Low RPM *lean* hesitations... Fuel-pump resistor relay?
04-10-08, 02:14 AM
#1
Low RPM *lean* hesitations... Fuel-pump resistor relay?
The RX-7 and it's background:
1987 Turbo II running stock ECU, FD fuel-pump, high-impedance s5 injectors, full emissions removal with block-off plates, free intake and exhaust, FD-alternator etc.
This car had been running perfectly in the past, but recently underwent some transformation. The ECU went from an (87) N332 with R-Tek, to a stock (88) N333. All of the grounds were redone at the ECU as recommended by HAILERS and others. The ECU is assumed to be in good-condition, but it's still an unknown variable until this problem is fixed.
The old AFM and pressure-sensor were also swapped for use in another vehicle several months ago. The current N318 AFM and N318 pressure-sensor were removed from a running/driving TII.
The s5 TII (high-impedance) injectors were swapped because I could not find my complete set of low-impedance s4 TII injectors. Because of this, I removed the fuel-injector resistor pack and spliced all of the wires as recommended when deleting the pack.
All of the engine-bay grounds were redone (in addition to the ECU-grounds), including an extra pressure-sensor ground, the small ground under the air-filter, the fuel-injector ground (on the engine-block), the tranny to firewall ground, the battery grounds and the coil-pack grounds.
All alternator, CAS and plug-wires have been heavily shielded for added "comfort" due to the higher-output FD-alternator mod that this TII has.
The problem:
The car starts great and fires right up. The engine revs freely at any RPM and is perfectly smooth. If warm, the engine can rest and hold a perfect 800 RPM idle. In first gear, the car will rev smoothly with basically any throttle imput, and at any RPM. The problem begins in second gear (or under more significant load)...
Upon shifting, and applying throttle, the engine will momentarily stumble, and if more throttle is initially added, the car will simply want to bog (for example, between 1500 and 2500 RPM's). After several moments, and with light throttle-play, the problem will go away and the engine can freely rev to the next shift point (example 4000 RPM's). Shifting into third gear, causes the same lower-RPM hesitation to occur. If the throttle is "eased" into, the problem does not exacerbate and the car will avoid obvious stumbling. Climbing a hill proves difficult because the added load makes the problem much more dramatic with additional popping and hesitation until the problem "rights itself" with some light throttle-play and increased RPM's. After the hesitation, the problem is minimized with higher RPM's and sustained load.
The problem also manifests itself in a different problem that at first seems unrelated... When I come to a stop, the idle will frequently drop dramatically--almost to the point of stalling before quickly righting itself and bumping up to normal.
I have measured the fuel-pump voltage and it stays between 10.3V and 10.6V and *does not change* during the hesitations and bogging, idle, normal-cruising and deceleration. This is not normal. The pump should see around 12V during load/cruise scenarios and approximately 9V at idle. I'm guessing 0V at deceleration should be seen?
The AFR's however, *DO* change, and change dramatically while the hesitations are occurring. Initially upon applying throttle (and experiencing the hesitations), the AFR's jump anywhere from the 15's to the 19's and the lean condition is increased depending on the amount of throttle. More initial throttle causes a greater lean condition to register on the wide-band, which means more hesitation and bogging. If throttle-play is used to let off the throttle and "ease" back into it, the problem is undramatic and hardly noticeable.
Monitoring the AFR's for the idle-problem, when coming to a stop and and letting the RPM's drop (with no throttle input), the AFR's will dramatically drop to the mid-20's, dropping the RPM's close to 0, before stabilizing (with much sputtering) and raising to a 800 RPM idle with mid-12 AFR's--as if nothing had happened.
Next step:
I have been troubleshooting this problem for several days now, and I initially thought it was a problem with alternator and CAS/spark interference. I swapped my FD alternator with an s5 alternator, but had serious issues because the s5 alternator did not have a dual-pulley and quickly ate a belt. I have since swapped the FD alternator back in, and spent some time shielding all of the 12V, spark-plug wires and CAS wiring. The alternator is still a somewhat unknown variable. The spark-plugs and plug wires were replaced, and (as mentioned) all grounds were cleaned and redone.
I have not checked the fuel-injector voltage yet, but am not quite sure how I should be doing this... Should I expose the ECU and use a multimeter to back-probe the various injector/plug wires to look for differences/voltage drop while the hesitations are occurring? I've never done this before.
Regarding the fuel-pump resistor relay... The 10.3V-10.7V is obviously low, and as mentioned does not change like it should. I'm guessing the problem *could* be that the relay is messed up, causing the resistor to clamp down on the voltage at all times (instead of letting it freely move from 9V at idle, to 12V under load). This would explain the constant voltage, and *might* explain the initial lean condition? I don't quite see this last part--but it could be that the fuel-delivery might have to "kick-start" it's way to a normal fuel-delivery with this lower voltage? Kind of a stretch--but I'm going to be removing the relay and will attempt a "direct-wire" to bypass it.
I have also not ruled out a bad fuel-pressure regulator (on the secondary fuel-rail), but this seems like an unlikely suspect simply because I've never really heard of them failing. However, I read that a bad regulator can cause a lean condition.
Other than this, I'm at a loss because I can't think of any variable that's been changed or tampered with.
Help?
1987 Turbo II running stock ECU, FD fuel-pump, high-impedance s5 injectors, full emissions removal with block-off plates, free intake and exhaust, FD-alternator etc.
This car had been running perfectly in the past, but recently underwent some transformation. The ECU went from an (87) N332 with R-Tek, to a stock (88) N333. All of the grounds were redone at the ECU as recommended by HAILERS and others. The ECU is assumed to be in good-condition, but it's still an unknown variable until this problem is fixed.
The old AFM and pressure-sensor were also swapped for use in another vehicle several months ago. The current N318 AFM and N318 pressure-sensor were removed from a running/driving TII.
The s5 TII (high-impedance) injectors were swapped because I could not find my complete set of low-impedance s4 TII injectors. Because of this, I removed the fuel-injector resistor pack and spliced all of the wires as recommended when deleting the pack.
All of the engine-bay grounds were redone (in addition to the ECU-grounds), including an extra pressure-sensor ground, the small ground under the air-filter, the fuel-injector ground (on the engine-block), the tranny to firewall ground, the battery grounds and the coil-pack grounds.
All alternator, CAS and plug-wires have been heavily shielded for added "comfort" due to the higher-output FD-alternator mod that this TII has.
The problem:
The car starts great and fires right up. The engine revs freely at any RPM and is perfectly smooth. If warm, the engine can rest and hold a perfect 800 RPM idle. In first gear, the car will rev smoothly with basically any throttle imput, and at any RPM. The problem begins in second gear (or under more significant load)...
Upon shifting, and applying throttle, the engine will momentarily stumble, and if more throttle is initially added, the car will simply want to bog (for example, between 1500 and 2500 RPM's). After several moments, and with light throttle-play, the problem will go away and the engine can freely rev to the next shift point (example 4000 RPM's). Shifting into third gear, causes the same lower-RPM hesitation to occur. If the throttle is "eased" into, the problem does not exacerbate and the car will avoid obvious stumbling. Climbing a hill proves difficult because the added load makes the problem much more dramatic with additional popping and hesitation until the problem "rights itself" with some light throttle-play and increased RPM's. After the hesitation, the problem is minimized with higher RPM's and sustained load.
The problem also manifests itself in a different problem that at first seems unrelated... When I come to a stop, the idle will frequently drop dramatically--almost to the point of stalling before quickly righting itself and bumping up to normal.
I have measured the fuel-pump voltage and it stays between 10.3V and 10.6V and *does not change* during the hesitations and bogging, idle, normal-cruising and deceleration. This is not normal. The pump should see around 12V during load/cruise scenarios and approximately 9V at idle. I'm guessing 0V at deceleration should be seen?
The AFR's however, *DO* change, and change dramatically while the hesitations are occurring. Initially upon applying throttle (and experiencing the hesitations), the AFR's jump anywhere from the 15's to the 19's and the lean condition is increased depending on the amount of throttle. More initial throttle causes a greater lean condition to register on the wide-band, which means more hesitation and bogging. If throttle-play is used to let off the throttle and "ease" back into it, the problem is undramatic and hardly noticeable.
Monitoring the AFR's for the idle-problem, when coming to a stop and and letting the RPM's drop (with no throttle input), the AFR's will dramatically drop to the mid-20's, dropping the RPM's close to 0, before stabilizing (with much sputtering) and raising to a 800 RPM idle with mid-12 AFR's--as if nothing had happened.
Next step:
I have been troubleshooting this problem for several days now, and I initially thought it was a problem with alternator and CAS/spark interference. I swapped my FD alternator with an s5 alternator, but had serious issues because the s5 alternator did not have a dual-pulley and quickly ate a belt. I have since swapped the FD alternator back in, and spent some time shielding all of the 12V, spark-plug wires and CAS wiring. The alternator is still a somewhat unknown variable. The spark-plugs and plug wires were replaced, and (as mentioned) all grounds were cleaned and redone.
I have not checked the fuel-injector voltage yet, but am not quite sure how I should be doing this... Should I expose the ECU and use a multimeter to back-probe the various injector/plug wires to look for differences/voltage drop while the hesitations are occurring? I've never done this before.
Regarding the fuel-pump resistor relay... The 10.3V-10.7V is obviously low, and as mentioned does not change like it should. I'm guessing the problem *could* be that the relay is messed up, causing the resistor to clamp down on the voltage at all times (instead of letting it freely move from 9V at idle, to 12V under load). This would explain the constant voltage, and *might* explain the initial lean condition? I don't quite see this last part--but it could be that the fuel-delivery might have to "kick-start" it's way to a normal fuel-delivery with this lower voltage? Kind of a stretch--but I'm going to be removing the relay and will attempt a "direct-wire" to bypass it.
I have also not ruled out a bad fuel-pressure regulator (on the secondary fuel-rail), but this seems like an unlikely suspect simply because I've never really heard of them failing. However, I read that a bad regulator can cause a lean condition.
Other than this, I'm at a loss because I can't think of any variable that's been changed or tampered with.
Help?
04-10-08, 02:23 AM
#2
"I have measured the fuel-pump voltage and it stays between 10.3V and 10.6V and *does not change* during the hesitations and bogging, idle, normal-cruising and deceleration. This is not normal. The pump should see around 12V during load/cruise scenarios and approximately 9V at idle. I'm guessing 0V at deceleration should be seen?"
I'm pretty sure 9-10V is the lowest the voltage is supposed to go while the motor is running. Furthermore I think fuel is still injected on decel, just not a whole lot. You are right though, it should see 12V under load and moderate load and up cruise conditions. I would also check your TPS just because it can frequently contribute to and cause problems. Search 'rewire fuel pump', there's a way to set up your fuel pump wiring to still work with the lower pump voltage when appropriate but if done right it should work better and last longer than the stock configuration.
I'm pretty sure 9-10V is the lowest the voltage is supposed to go while the motor is running. Furthermore I think fuel is still injected on decel, just not a whole lot. You are right though, it should see 12V under load and moderate load and up cruise conditions. I would also check your TPS just because it can frequently contribute to and cause problems. Search 'rewire fuel pump', there's a way to set up your fuel pump wiring to still work with the lower pump voltage when appropriate but if done right it should work better and last longer than the stock configuration.
04-10-08, 03:25 AM
#3
ive got the exact same problem, im pretty sure its my injector connectors, i tugged on them while replacing a fuel hose, because i kept having to pull it off to change the size.
Ever since then my car has had this problem.
I'm putting in a haltech soon though, so im not very worried about it.
Ever since then my car has had this problem.
I'm putting in a haltech soon though, so im not very worried about it.
04-10-08, 03:47 AM
#4
"I have measured the fuel-pump voltage and it stays between 10.3V and 10.6V and *does not change* during the hesitations and bogging, idle, normal-cruising and deceleration. This is not normal. The pump should see around 12V during load/cruise scenarios and approximately 9V at idle. I'm guessing 0V at deceleration should be seen?"
I'm pretty sure 9-10V is the lowest the voltage is supposed to go while the motor is running. Furthermore I think fuel is still injected on decel, just not a whole lot. You are right though, it should see 12V under load and moderate load and up cruise conditions. I would also check your TPS just because it can frequently contribute to and cause problems. Search 'rewire fuel pump', there's a way to set up your fuel pump wiring to still work with the lower pump voltage when appropriate but if done right it should work better and last longer than the stock configuration.
I'm pretty sure 9-10V is the lowest the voltage is supposed to go while the motor is running. Furthermore I think fuel is still injected on decel, just not a whole lot. You are right though, it should see 12V under load and moderate load and up cruise conditions. I would also check your TPS just because it can frequently contribute to and cause problems. Search 'rewire fuel pump', there's a way to set up your fuel pump wiring to still work with the lower pump voltage when appropriate but if done right it should work better and last longer than the stock configuration.
Originally Posted by HAILERS
12vdc when starting.............drops to approx 9vdc while idleing (sp).........back to alternator output when you have a load on the engine.
Originally Posted by HAILERS
This is because when you just barely let off the front rotor gets cuts fuel and only the front rotor (see Training Manual)
IF you let off quite a bit, then both rotors have fuel cut off and the afr goes to ?????21-22afr. Depends on the widebands range.
IF you let off quite a bit, then both rotors have fuel cut off and the afr goes to ?????21-22afr. Depends on the widebands range.
(I should've mentioned) That being said, I have been having a minor issue with "sticky" throttle-linkage causing a slight 2-stage idle--meaning at "one" idle the TPS is set correctly, but the other (higher) idle would be off. If the voltage to the fuel-pump remains below 11V after bypassing the fuel-pump resistor/relay then I will rewire the fuel-pump--even if it's unrelated to this specific problem.
Originally Posted by TehMonkay
ive got the exact same problem, im pretty sure its my injector connectors, i tugged on them while replacing a fuel hose, because i kept having to pull it off to change the size.
Ever since then my car has had this problem.
I'm putting in a haltech soon though, so im not very worried about it.
Ever since then my car has had this problem.
I'm putting in a haltech soon though, so im not very worried about it.
The reason why I don't think I simply have a "loose" connection at one or both of the primary injector-plugs is because the problem happens in exactly the same way every time, and a loose connection would imply erratic behavior. The symptoms I'm dealing with involve lean conditions based upon several observed variables.
Thanks again for the replies!
04-10-08, 04:46 PM
#5
New findings:
I bypassed the fuel-pump resistor relay by cutting the Green/Red wire coming into the resistor-relay (engine-bay). From what I've read, this means that the ECU cannot "put a ground" on the relay (which in turn would force the voltage through the resistor). This is supposed to allow full battery/alternator voltage at all times to the fuel-pump, instead of "resisting" it to 9V during idle and light-load.
Anyways, I saw no change in the fuel-pump voltage and it remained a steady 10.3V-10.7V. I don't know what this means about the condition of my resistor/relay--but it does mean that a fuel-pump rewire is in order, even though I'm pretty sure a rewire won't fix whatever problem I'm dealing with.
Interesting observation:
I think I have found an important "lead" in this puzzle... Let me try to explain:
Occasionally the idle will remain "high" when coming to a stop (now in neutral)--let's say around 1300 RPM's. However, if I put the transmission IN GEAR, the engine will literally CUT FUEL, which drops the idle to it's "normal" 800 RPM's. :
WHAT *SYSTEM* CAUSES THIS?
If I leave the transmission IN GEAR (any gear) and attempt to "free rev" the engine with the clutch pedal pushed in, the engine will refuse to "hold" a steady RPM below 2000 RPM's... So for example, if I slowly increase the REV's to 1500 RPM's (in gear), the engine will reach a point and CUT FUEL, which drops the REV's well below 1000 RPM's before correcting itself and coming back up. It will do the exact same thing all the way up to nearly 2000 RPM's--reaching a point at which the fuel is literally CUT (16-20 AFR's), dropping the RPM's significantly. The entire time the accelerator-pedal is held at a sustained position... If I were to hold my foot in the same position indefinitely (for example, 1800 RPM's), then the engine would basically just pulse... The RPM's would increase to about 1800 RPM's, and then the fuel would be cut, the RPM's would drop back down and then the RPM's would increase after "correcting" itself--and it would go on forever...
In juxtaposition, if I were to simply place the shifter in NEUTRAL and change NO OTHER VARIABLE, then "magically" there would be NO FUEL-CUT at any point in the lower-RPM's and I could "free rev" to my hearts content... The only variable is that the transmission is in gear...
Whatever is causing this to happen--I guarantee that this is also the source of my drivability problem... Think about it. I'm cruising down the road, IN GEAR, in the lower-RPM's when for whatever reason the engine starts bucking and I register lean-spikes on my wideband. Just like what happens when I'm stationary and I "simulate" cruising down the road (by slowly increasing rev's in the lower RPM's).
Any clues?
I bypassed the fuel-pump resistor relay by cutting the Green/Red wire coming into the resistor-relay (engine-bay). From what I've read, this means that the ECU cannot "put a ground" on the relay (which in turn would force the voltage through the resistor). This is supposed to allow full battery/alternator voltage at all times to the fuel-pump, instead of "resisting" it to 9V during idle and light-load.
Anyways, I saw no change in the fuel-pump voltage and it remained a steady 10.3V-10.7V. I don't know what this means about the condition of my resistor/relay--but it does mean that a fuel-pump rewire is in order, even though I'm pretty sure a rewire won't fix whatever problem I'm dealing with.
Interesting observation:
I think I have found an important "lead" in this puzzle... Let me try to explain:
Occasionally the idle will remain "high" when coming to a stop (now in neutral)--let's say around 1300 RPM's. However, if I put the transmission IN GEAR, the engine will literally CUT FUEL, which drops the idle to it's "normal" 800 RPM's. :
WHAT *SYSTEM* CAUSES THIS?If I leave the transmission IN GEAR (any gear) and attempt to "free rev" the engine with the clutch pedal pushed in, the engine will refuse to "hold" a steady RPM below 2000 RPM's... So for example, if I slowly increase the REV's to 1500 RPM's (in gear), the engine will reach a point and CUT FUEL, which drops the REV's well below 1000 RPM's before correcting itself and coming back up. It will do the exact same thing all the way up to nearly 2000 RPM's--reaching a point at which the fuel is literally CUT (16-20 AFR's), dropping the RPM's significantly. The entire time the accelerator-pedal is held at a sustained position... If I were to hold my foot in the same position indefinitely (for example, 1800 RPM's), then the engine would basically just pulse... The RPM's would increase to about 1800 RPM's, and then the fuel would be cut, the RPM's would drop back down and then the RPM's would increase after "correcting" itself--and it would go on forever...
In juxtaposition, if I were to simply place the shifter in NEUTRAL and change NO OTHER VARIABLE, then "magically" there would be NO FUEL-CUT at any point in the lower-RPM's and I could "free rev" to my hearts content... The only variable is that the transmission is in gear...
Whatever is causing this to happen--I guarantee that this is also the source of my drivability problem... Think about it. I'm cruising down the road, IN GEAR, in the lower-RPM's when for whatever reason the engine starts bucking and I register lean-spikes on my wideband. Just like what happens when I'm stationary and I "simulate" cruising down the road (by slowly increasing rev's in the lower RPM's).
Any clues?
Last edited by eriksseven; 04-10-08 at 04:51 PM.
04-10-08, 08:53 PM
#6
More findings:
I mentioned "sticky" throttle-linkage previously, and decided to remove the TB to make sure there was no interference from any of the various TB screws, stops, dash-pots or whatever. I also noticed that the "scissor-like" brass-colored linkage-components--that together manipulate the TPS (with the spring and screw for adjustment) had a very difficult time coming to a rest. In essence, I could "set" the TPS, but the spring was not strong enough to "push" the linkage back to my setting. It was very sticky. I removed the front 12mm nut on the throttle-"rod" that goes from the front of the TB, to the back and cleaned everything to insure smooth TPS operation. This was successful and the TPS is fully able to respond (and return) with throttle-operation. THIS DID NOT FIX THE PROBLEM, and I am still getting a "two stage" idle that drops significantly once the car is put into gear...
I also replaced the fuel-pressure regulator. THIS DID NOT FIX THE PROBLEM--and I'm still seeing hesitations with 16-19 AFR's during the low-RPM's when applying throttle.
I also removed the alternator belts and unplugged it to fully eliminate the "spark interference" variable. THIS DID NOT FIX THE PROBLEM.
Next step is to monitor all of the ECU pin-outs while the problem is occurring, for any unusual activity that could remotely be related. Fuel-injectors etc.
Any advice at this point would be greatly appreciated. My main question is:
What system has the ability to cut fuel if the transmission is put into gear?
Note: I noticed my E-BRAKE idiot light flickered as I repeatedly revved the engine in neutral up to it's "idle spot", before putting the transmission in gear and watching as fuel was cut and the RPM's dropped to the "other" much lower idle...
I mentioned "sticky" throttle-linkage previously, and decided to remove the TB to make sure there was no interference from any of the various TB screws, stops, dash-pots or whatever. I also noticed that the "scissor-like" brass-colored linkage-components--that together manipulate the TPS (with the spring and screw for adjustment) had a very difficult time coming to a rest. In essence, I could "set" the TPS, but the spring was not strong enough to "push" the linkage back to my setting. It was very sticky. I removed the front 12mm nut on the throttle-"rod" that goes from the front of the TB, to the back and cleaned everything to insure smooth TPS operation. This was successful and the TPS is fully able to respond (and return) with throttle-operation. THIS DID NOT FIX THE PROBLEM, and I am still getting a "two stage" idle that drops significantly once the car is put into gear...
I also replaced the fuel-pressure regulator. THIS DID NOT FIX THE PROBLEM--and I'm still seeing hesitations with 16-19 AFR's during the low-RPM's when applying throttle.
I also removed the alternator belts and unplugged it to fully eliminate the "spark interference" variable. THIS DID NOT FIX THE PROBLEM.
Next step is to monitor all of the ECU pin-outs while the problem is occurring, for any unusual activity that could remotely be related. Fuel-injectors etc.
Any advice at this point would be greatly appreciated.
My main question is:What system has the ability to cut fuel if the transmission is put into gear?
Note: I noticed my E-BRAKE idiot light flickered as I repeatedly revved the engine in neutral up to it's "idle spot", before putting the transmission in gear and watching as fuel was cut and the RPM's dropped to the "other" much lower idle...
04-11-08, 03:28 PM
#7
HAILERS
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Under Load the voltage at the pump should go to whatever the alternator is putting out. It does this by removing the gnd from green/red wire at the fuel pump resistor relay. I *think* the pin on the ECU is pin 3D on a series four. IF you depin that wire at the ECU, the voltage should rise to alternator output voltage, FROM whatever it is at idle. The FSM says 9vdc but in real life with a good alternator output it'll be a bit higher. Like 10 to 10 1/2 volts or so. Remove that green/red wire and the voltage should immediatley go in the upper 13's or low 14's. Just remove that wire from the ECU plug temp and see if the voltage goes up or not from what your seeing right now.
If the voltage isn't rising when you get into boost/load, then go to the pin 2B which is the output of the boost sensor to the ECU (2.3 to 2.7 vdc or real close to that), and see if that voltage is right or not. It's stated in the FSM, Fuel and Emissions section, section called Control Unit. You could just backprobe 2B and look at the voltage at idle then go around the block and go into boost just a touch and see if the voltage rises or not. Should.
When you let off the throttle, the fuel gets cut, but not by the fuel pump. The ECU shuts off the fuel injectors. IF you lift off completly both front and rear injectors cut off. If you just barely let off the throttle, just the front rotor gets the fuel cut by the injector/ECU.
Yeah. Go to the CONTROL UNIT section that gives the output/input of each wire on the ECU wires and compare it with what you have.
If the voltage isn't rising when you get into boost/load, then go to the pin 2B which is the output of the boost sensor to the ECU (2.3 to 2.7 vdc or real close to that), and see if that voltage is right or not. It's stated in the FSM, Fuel and Emissions section, section called Control Unit. You could just backprobe 2B and look at the voltage at idle then go around the block and go into boost just a touch and see if the voltage rises or not. Should.
When you let off the throttle, the fuel gets cut, but not by the fuel pump. The ECU shuts off the fuel injectors. IF you lift off completly both front and rear injectors cut off. If you just barely let off the throttle, just the front rotor gets the fuel cut by the injector/ECU.
Yeah. Go to the CONTROL UNIT section that gives the output/input of each wire on the ECU wires and compare it with what you have.
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04-11-08, 04:28 PM
#8
Under Load the voltage at the pump should go to whatever the alternator is putting out. It does this by removing the gnd from green/red wire at the fuel pump resistor relay. I *think* the pin on the ECU is pin 3D on a series four. IF you depin that wire at the ECU, the voltage should rise to alternator output voltage, FROM whatever it is at idle. The FSM says 9vdc but in real life with a good alternator output it'll be a bit higher. Like 10 to 10 1/2 volts or so. Remove that green/red wire and the voltage should immediatley go in the upper 13's or low 14's. Just remove that wire from the ECU plug temp and see if the voltage goes up or not from what your seeing right now.
If the voltage isn't rising when you get into boost/load, then go to the pin 2B which is the output of the boost sensor to the ECU (2.3 to 2.7 vdc or real close to that), and see if that voltage is right or not. It's stated in the FSM, Fuel and Emissions section, section called Control Unit. You could just backprobe 2B and look at the voltage at idle then go around the block and go into boost just a touch and see if the voltage rises or not. Should.
When you let off the throttle, the fuel gets cut, but not by the fuel pump. The ECU shuts off the fuel injectors. IF you lift off completly both front and rear injectors cut off. If you just barely let off the throttle, just the front rotor gets the fuel cut by the injector/ECU.
Yeah. Go to the CONTROL UNIT section that gives the output/input of each wire on the ECU wires and compare it with what you have.
When you let off the throttle, the fuel gets cut, but not by the fuel pump. The ECU shuts off the fuel injectors. IF you lift off completly both front and rear injectors cut off. If you just barely let off the throttle, just the front rotor gets the fuel cut by the injector/ECU.
Yeah. Go to the CONTROL UNIT section that gives the output/input of each wire on the ECU wires and compare it with what you have.
04-11-08, 06:31 PM
#9
HAILERS
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Is this a stock installation of the fuel pump resistor relay? Voltage should have gone up with the green/red wire removed.
There should be two blue/red wires in the fuel pump resistor relay plug. Both are the same and come from the circuit opening relay. I'd ***** one of the two blue/red wires and put a meter to it to see what the voltage is coming into the fuel pump resistor relay with the engine running. If it's alternator voltage, then ***** the pure BLUE wires leaving that fuel pump resistor relay plug. It should be the same voltage as the Blue/Red wires. IF not, then I'd guess the relay inside the fuel pump resistor relay package is stuck.
I'd do that before doing the other things mentioned.
To depin a wire from a ECU plug, you pull the plug off the ECU. You look into the end of the plug opposite the wires. You depress the small tongue while pulling on the wire from the other end. Wire comes out with no damage.
There should be two blue/red wires in the fuel pump resistor relay plug. Both are the same and come from the circuit opening relay. I'd ***** one of the two blue/red wires and put a meter to it to see what the voltage is coming into the fuel pump resistor relay with the engine running. If it's alternator voltage, then ***** the pure BLUE wires leaving that fuel pump resistor relay plug. It should be the same voltage as the Blue/Red wires. IF not, then I'd guess the relay inside the fuel pump resistor relay package is stuck.
I'd do that before doing the other things mentioned.
To depin a wire from a ECU plug, you pull the plug off the ECU. You look into the end of the plug opposite the wires. You depress the small tongue while pulling on the wire from the other end. Wire comes out with no damage.
04-11-08, 10:22 PM
#10
Is this a stock installation of the fuel pump resistor relay? Voltage should have gone up with the green/red wire removed.
There should be two blue/red wires in the fuel pump resistor relay plug. Both are the same and come from the circuit opening relay. I'd ***** one of the two blue/red wires and put a meter to it to see what the voltage is coming into the fuel pump resistor relay with the engine running. If it's alternator voltage, then ***** the pure BLUE wires leaving that fuel pump resistor relay plug. It should be the same voltage as the Blue/Red wires. IF not, then I'd guess the relay inside the fuel pump resistor relay package is stuck.
I'd do that before doing the other things mentioned.
To depin a wire from a ECU plug, you pull the plug off the ECU. You look into the end of the plug opposite the wires. You depress the small tongue while pulling on the wire from the other end. Wire comes out with no damage.
There should be two blue/red wires in the fuel pump resistor relay plug. Both are the same and come from the circuit opening relay. I'd ***** one of the two blue/red wires and put a meter to it to see what the voltage is coming into the fuel pump resistor relay with the engine running. If it's alternator voltage, then ***** the pure BLUE wires leaving that fuel pump resistor relay plug. It should be the same voltage as the Blue/Red wires. IF not, then I'd guess the relay inside the fuel pump resistor relay package is stuck.
I'd do that before doing the other things mentioned.
To depin a wire from a ECU plug, you pull the plug off the ECU. You look into the end of the plug opposite the wires. You depress the small tongue while pulling on the wire from the other end. Wire comes out with no damage.
04-12-08, 03:11 PM
#11
Wow... This is where someone E-slaps me. 
As I was trying to delve into the ridiculous and technical workings of the FC, the "problem" was laughing at me, deep within the engine-bay... Can anyone guess what it turned out to be? And no, it wasn't the fuel-pump resistor relay--nor was it some complicated ECU electrical-gremlin that I've been foolishly stressing out about and hunting for, for days.
Clues: It's a common, off-the-shelf generic item.
And yes, I can be E-slapped again. 
Either way, my days are now filled with joy and peace as I rip around in this now *perfect* running RX-7!
As I was trying to delve into the ridiculous and technical workings of the FC, the "problem" was laughing at me, deep within the engine-bay... Can anyone guess what it turned out to be? And no, it wasn't the fuel-pump resistor relay--nor was it some complicated ECU electrical-gremlin that I've been foolishly stressing out about and hunting for, for days.
Clues: It's a common, off-the-shelf generic item.
And yes, I can be E-slapped again.
Either way, my days are now filled with joy and peace as I rip around in this now *perfect* running RX-7!
04-12-08, 03:49 PM
#13
HAILERS
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I meant to say earlier, that low rpms and low load wouldn't be be a fuel pump resistor relay problem since the voltage is always low under the above.
I've no idea what caused your problem.
I've no idea what caused your problem.
04-12-08, 03:58 PM
#14
Bad fuel-filter... 
I know it sounds n00bish, but the filter was less than 6 months old with around 8k miles on it. I discounted it almost immediately after noticing the problem because (in my mind) it had already been "replaced"... Either way, not sure if it was from running pre-mix and then having it sit for a while, or if something "got into it" while the engine-bay was being painted.
Either way, I woke up this morning with the idea (crossing my fingers), threw a new one in there and WA-LA... Pure rotary perfection.
Thanks for the input HAILERS, speed and monkay. You provide hope and motivation! Not saying I would ever give up when trouble-shooting a problem, but it's always nice to hear from other members!
I know it sounds n00bish, but the filter was less than 6 months old with around 8k miles on it. I discounted it almost immediately after noticing the problem because (in my mind) it had already been "replaced"... Either way, not sure if it was from running pre-mix and then having it sit for a while, or if something "got into it" while the engine-bay was being painted.
Either way, I woke up this morning with the idea (crossing my fingers), threw a new one in there and WA-LA... Pure rotary perfection.
Thanks for the input HAILERS, speed and monkay. You provide hope and motivation!
Not saying I would ever give up when trouble-shooting a problem, but it's always nice to hear from other members!
04-23-08, 08:34 PM
#16
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similar problem
I have an 86 na car with an 88 jdm engine. it is running extremely lean and i actually went out to check everything under the hood tonight to find that my turbo and downpipe were glowing cherry red. When i hit the throttle hard, i can usually accelerate ok through 1st gear and most of 2nd gear. when i start to build boost in 3rd, it feels like the fuel is cut and the car starts bucking, sputtering, and shaking. to me this seems like a lean condition. i have an fmic, boost controller, and a beigi rising rate fpr, 255lph fuel pump(12v at all times) Everything else as far as engine management goes is from a stock tii.
Does anyone have any clues as to what i may have going on? feel free to ask me anything if you need more info to help
ps....im tapped at the moment, and unfortunately do not have a wideband o2 sensor yet
Does anyone have any clues as to what i may have going on? feel free to ask me anything if you need more info to help
ps....im tapped at the moment, and unfortunately do not have a wideband o2 sensor yet
06-17-08, 02:47 PM
#17
Exhaust Manifold Leak
Hi,
I still have the problem with my FC series 5 convertible..
I measured fuel pressure after the fuel filter, stays above 2 bar at anytime so that isn't the problem..
I checked the TPS according to the manual, and the position was still fine..
Under higher load the car drives very well.. It has a knightsports big compressor kit, and 3" exhausqt with cat..
So under light load in the 2000-4000rpm range it just leans out, afr goes to 21 and the car stumbles.. I noticed the problem is worse when driving with the lights on.. alternator seems fine, batterij voltage stays arounnd 14v when driving..
I now tried a 20B mass airflow meter and open airfilter, problem is the same.. all the emissions crap is removed.. could it be a ground problem somewhere? I checked the ground under the airfilter, and the ecu ground and the gorund at the intercooler support, and they all look very clean..
the problem looks a bit like the ecu wants to lean out the primaries as the secondaries are coming online, but it happens a very light load under vacuum so the secondaries should not come online..
any one has some things I can try?
I still have the problem with my FC series 5 convertible..
I measured fuel pressure after the fuel filter, stays above 2 bar at anytime so that isn't the problem..
I checked the TPS according to the manual, and the position was still fine..
Under higher load the car drives very well.. It has a knightsports big compressor kit, and 3" exhausqt with cat..
So under light load in the 2000-4000rpm range it just leans out, afr goes to 21 and the car stumbles.. I noticed the problem is worse when driving with the lights on.. alternator seems fine, batterij voltage stays arounnd 14v when driving..
I now tried a 20B mass airflow meter and open airfilter, problem is the same.. all the emissions crap is removed.. could it be a ground problem somewhere? I checked the ground under the airfilter, and the ecu ground and the gorund at the intercooler support, and they all look very clean..
the problem looks a bit like the ecu wants to lean out the primaries as the secondaries are coming online, but it happens a very light load under vacuum so the secondaries should not come online..
any one has some things I can try?
06-17-08, 09:47 PM
#18
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Hi,
I still have the problem with my FC series 5 convertible..
I measured fuel pressure after the fuel filter, stays above 2 bar at anytime so that isn't the problem..
I checked the TPS according to the manual, and the position was still fine..
Under higher load the car drives very well.. It has a knightsports big compressor kit, and 3" exhausqt with cat..
So under light load in the 2000-4000rpm range it just leans out, afr goes to 21 and the car stumbles.. I noticed the problem is worse when driving with the lights on.. alternator seems fine, batterij voltage stays arounnd 14v when driving..
I now tried a 20B mass airflow meter and open airfilter, problem is the same.. all the emissions crap is removed.. could it be a ground problem somewhere? I checked the ground under the airfilter, and the ecu ground and the gorund at the intercooler support, and they all look very clean..
the problem looks a bit like the ecu wants to lean out the primaries as the secondaries are coming online, but it happens a very light load under vacuum so the secondaries should not come online..
any one has some things I can try?
I still have the problem with my FC series 5 convertible..
I measured fuel pressure after the fuel filter, stays above 2 bar at anytime so that isn't the problem..
I checked the TPS according to the manual, and the position was still fine..
Under higher load the car drives very well.. It has a knightsports big compressor kit, and 3" exhausqt with cat..
So under light load in the 2000-4000rpm range it just leans out, afr goes to 21 and the car stumbles.. I noticed the problem is worse when driving with the lights on.. alternator seems fine, batterij voltage stays arounnd 14v when driving..
I now tried a 20B mass airflow meter and open airfilter, problem is the same.. all the emissions crap is removed.. could it be a ground problem somewhere? I checked the ground under the airfilter, and the ecu ground and the gorund at the intercooler support, and they all look very clean..
the problem looks a bit like the ecu wants to lean out the primaries as the secondaries are coming online, but it happens a very light load under vacuum so the secondaries should not come online..
any one has some things I can try?
06-18-08, 02:40 AM
#19
Exhaust Manifold Leak
no, it happens between 2000-4000rpm under closed loop operation.. then after a sec or two at that light load, like when taking a round-about in 2nd gear, afr goes to 21, when you get of the throttle or give mroe throttle it goes away..
I have a zeitronix wideband gauge with narrowband output for the ecu.. mostly closed loop operation works very good, and afr is close to 14.7 then, but just sometimes, especially with the lights on it lean out and stumbles hard.. :/
I have a zeitronix wideband gauge with narrowband output for the ecu.. mostly closed loop operation works very good, and afr is close to 14.7 then, but just sometimes, especially with the lights on it lean out and stumbles hard.. :/
06-19-08, 04:22 AM
#20
This thread is incomplete.
My problem was NOT the fuel-filter, it was actually poorly seated fuel-injector grommets. The injector grommets that I received with my freshly cleaned injectors were slightly too "short" and were not firmly sealing. I had removed the injectors several times during trouble-shooting and ironically re-sealed them at the same time I also replaced my fuel-filter. It made me attribute the better AFR's to the filter and NOT to the real culprit which were the injector seals.
To check your fuel-injector grommets/seals, spray a TON of carb/brake fluid/starter fluid onto your injectors while the car is idling. If there is any change in the idle, then you've discovered a poorly sealing injector which should get new grommets/rubber boots ASAP.
My problem was NOT the fuel-filter, it was actually poorly seated fuel-injector grommets. The injector grommets that I received with my freshly cleaned injectors were slightly too "short" and were not firmly sealing. I had removed the injectors several times during trouble-shooting and ironically re-sealed them at the same time I also replaced my fuel-filter. It made me attribute the better AFR's to the filter and NOT to the real culprit which were the injector seals.
To check your fuel-injector grommets/seals, spray a TON of carb/brake fluid/starter fluid onto your injectors while the car is idling. If there is any change in the idle, then you've discovered a poorly sealing injector which should get new grommets/rubber boots ASAP.
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trickster
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