3k RPM hesitation - INTERESTING !
11-12-03, 04:34 AM
#26
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Cruiser i have an european FD and i DO have that damned hesitation, even i think it is a problem with O2 sensor or maybe fuel pump/pressure regulator...
i tryed grounding but nothing changed.
For me it happens only with light acceleration, some times it last only a fraction of a second, other times more than one seconds , causing the car to stumble a lot
i tryed grounding but nothing changed.
For me it happens only with light acceleration, some times it last only a fraction of a second, other times more than one seconds , causing the car to stumble a lot
11-12-03, 10:22 AM
#28
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You got the M2 Stage 3?
maybe with chipped ecus they changed a parameter that sets the rpm at which the fuel pump changes speed but i'm not sure of this
even in the power FC i cannot see any param that controls it even with datalogit
the fact is that i don't have it all the times
in any case that damned hesi is really weird...
BTW i wanted to change the fuel pump
any of you knows where to get a new stock one at reasonable prices or a replacement one (maybe a little bigger than original) that can work with stock ecu or so?
maybe with chipped ecus they changed a parameter that sets the rpm at which the fuel pump changes speed but i'm not sure of this
even in the power FC i cannot see any param that controls it even with datalogit
the fact is that i don't have it all the times
in any case that damned hesi is really weird...
BTW i wanted to change the fuel pump
any of you knows where to get a new stock one at reasonable prices or a replacement one (maybe a little bigger than original) that can work with stock ecu or so?
11-12-03, 10:55 AM
#29
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I have extra grounding and a brand new Cosmo fuel pump but yet still have the hesitation.
I agreee with Max. you need to drive around on the ECU so that it will learn some of the settings. Then see if you hesitation goes away. Every time I remove the power to the ECU the hesitation will go away.
I'm going to swap out my 5 year old battery and try removing the hose for the fuel pressure regulator.
-Jeff
I agreee with Max. you need to drive around on the ECU so that it will learn some of the settings. Then see if you hesitation goes away. Every time I remove the power to the ECU the hesitation will go away.
I'm going to swap out my 5 year old battery and try removing the hose for the fuel pressure regulator.
-Jeff
Originally posted by maxcooper
I'm not the first person to suggest this, but the 3K hesitation seems to be the result of a number of different factors, and may even have totally different causes from car to car.
I had the 3K hesitation for a long time. I got a PowerFC and it was totally gone and I never had it again. The PowerFC seems to be a sure-fire solution. My car drove MUCH better after the PowerFC install.
But that doesn't mean that the ECU is the only cause. It could be several other factors that all "conspire" with the ECU to give you a hesitation. You might put that same ECU into another car and it would have no hesitation because the other circumstances aren't there to give the hesitiation.
Grounding has been a highly touted solution for a long time. It did not work on my car in the long term. I believe that many of the ground strap success stories are the result of someone resetting the ECU by disconnecting the ground terminal from the battery while working on the car and then declaring success when they hook everything back up and the hesitation is gone or reduced. After the ECU has a little time to (mal)adapt to the car again, the hesitation comes back. But you don't see many of those posts -- its no fun to report the return of a gremlin. And then again, bad grounds may be one of the conspititors in some instances of the hesitiation and it is possible that the ground strap really does fix it. But ground straps did not provide a lasting fix on my car.
-Max
I'm not the first person to suggest this, but the 3K hesitation seems to be the result of a number of different factors, and may even have totally different causes from car to car.
I had the 3K hesitation for a long time. I got a PowerFC and it was totally gone and I never had it again. The PowerFC seems to be a sure-fire solution. My car drove MUCH better after the PowerFC install.
But that doesn't mean that the ECU is the only cause. It could be several other factors that all "conspire" with the ECU to give you a hesitation. You might put that same ECU into another car and it would have no hesitation because the other circumstances aren't there to give the hesitiation.
Grounding has been a highly touted solution for a long time. It did not work on my car in the long term. I believe that many of the ground strap success stories are the result of someone resetting the ECU by disconnecting the ground terminal from the battery while working on the car and then declaring success when they hook everything back up and the hesitation is gone or reduced. After the ECU has a little time to (mal)adapt to the car again, the hesitation comes back. But you don't see many of those posts -- its no fun to report the return of a gremlin. And then again, bad grounds may be one of the conspititors in some instances of the hesitiation and it is possible that the ground strap really does fix it. But ground straps did not provide a lasting fix on my car.
-Max
11-12-03, 10:59 AM
#30
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I think the capacitor is a great idea. And I too think the hesitation is due to the voltage drop when the solenoids come online.
How about adding grounds directly to the ECU input wires? I'm also thinking of adding a relay with power directly from the battery to the power inputs of the ECU.
-Jeff
How about adding grounds directly to the ECU input wires? I'm also thinking of adding a relay with power directly from the battery to the power inputs of the ECU.
-Jeff
Originally posted by James Paventi
I added a battery to frame and bat to engine ground on my 7. This made a noticeable difference. However my hesitation has definitely not left.
I’ve read some threads that blame a sort of valve cracking or wearing out in the fuel pump, grounds, the fuel pump not transitioning from high to low quick enough, different ECU firmware versions, etc. I think that any of these are reasonable explanations but no single one is the silver bullet. That is there are probably several possible explanations outside of the ECU.
My current theory (in my car) is that the ECU isn’t supplied enough current to properly open the secondary set of injectors (around 3K RPMs). Once the inrush current of opening the secondarys is over with everything is OK. If this is true, why does the hesitation not exist under heavy boost? I don’t know. I haven’t had the change to track down the positive and negative (other than ECU case ground) power inputs to the ECU. When I do have a chance, I’m going to buffer the inputs with a large capacitor … something similar to what is done on high powered stereo amps. It’s just a guess … I may find nothing or it may solve it for me. I’ve read threads where a fuel pressure gauge gave away the fuel pump valve problem and others that showed perfect fuel pressure during the hesitation. What I’m saying is that there are probably several problems that cause the hesitation … much like the sequential turbo system malfunctions in so many ways.
I added a battery to frame and bat to engine ground on my 7. This made a noticeable difference. However my hesitation has definitely not left.
I’ve read some threads that blame a sort of valve cracking or wearing out in the fuel pump, grounds, the fuel pump not transitioning from high to low quick enough, different ECU firmware versions, etc. I think that any of these are reasonable explanations but no single one is the silver bullet. That is there are probably several possible explanations outside of the ECU.
My current theory (in my car) is that the ECU isn’t supplied enough current to properly open the secondary set of injectors (around 3K RPMs). Once the inrush current of opening the secondarys is over with everything is OK. If this is true, why does the hesitation not exist under heavy boost? I don’t know. I haven’t had the change to track down the positive and negative (other than ECU case ground) power inputs to the ECU. When I do have a chance, I’m going to buffer the inputs with a large capacitor … something similar to what is done on high powered stereo amps. It’s just a guess … I may find nothing or it may solve it for me. I’ve read threads where a fuel pressure gauge gave away the fuel pump valve problem and others that showed perfect fuel pressure during the hesitation. What I’m saying is that there are probably several problems that cause the hesitation … much like the sequential turbo system malfunctions in so many ways.
11-12-03, 03:08 PM
#31
It might help to bring a heave gauge power (positive) wire directly to the ECU ... say 10 gauge.
I'm not so sure that a ground wire to the ECU would help though. The ECU is housed in a metal case that is grounded by it's mounting bolts. It's a well designed ground that connects strait to the frame. This may be why grounding the frame (hyperground style) helps a bit.
I'm currently thinking of relocating my battery to make some room in the engine bay. After this, I'll add the capacitor where the battery was and or try directly powering the injectors.
What I mean by that last power to the injector comment is to bring a heavy gauge (switched via relay) wire to each injector. See this thread https://www.rx7club.com/showthread.p...readid=237041. Tim, I'm really curious how much a new battery helps you.
I'm not so sure that a ground wire to the ECU would help though. The ECU is housed in a metal case that is grounded by it's mounting bolts. It's a well designed ground that connects strait to the frame. This may be why grounding the frame (hyperground style) helps a bit.
I'm currently thinking of relocating my battery to make some room in the engine bay. After this, I'll add the capacitor where the battery was and or try directly powering the injectors.
What I mean by that last power to the injector comment is to bring a heavy gauge (switched via relay) wire to each injector. See this thread https://www.rx7club.com/showthread.p...readid=237041. Tim, I'm really curious how much a new battery helps you.
Originally posted by rx713bt
I think the capacitor is a great idea. And I too think the hesitation is due to the voltage drop when the solenoids come online.
How about adding grounds directly to the ECU input wires? I'm also thinking of adding a relay with power directly from the battery to the power inputs of the ECU.
-Jeff
I think the capacitor is a great idea. And I too think the hesitation is due to the voltage drop when the solenoids come online.
How about adding grounds directly to the ECU input wires? I'm also thinking of adding a relay with power directly from the battery to the power inputs of the ECU.
-Jeff
11-12-03, 04:04 PM
#32
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i was wondering if any one else has taken their computer apart. the cage is made of aluminum which oxidizes over time. i actually took off some of the internal grounds from the computer to the case and cleaned those. this helped some for the hesitation. if the computer is having internal grounding issues over time that could explain alot. it could affect different systems depoending on which ground is loosing continuity. adding external ground staps everywhere would help mask the internal grounfding issues
just a thought
jury
just a thought
jury
11-12-03, 04:09 PM
#33
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Hesitant
I had the 3k hesitation. So i ground the engine, down pipe, cat etcc... the standard wiring ground still exists on the standard ecu. I guess i should ground the ECU to the engine and then from the engin eto the negative battery terminal right?
However, i did notice that a grounding wire had broken away from from my ecu. Regrounded that and also sprayed a battery terminal protection solution on any exposed connections. I also replaced the oxy sensor.
Now i find the acceleration is much smoother and hestitation is not present. However, every so often the cheeky b4$tard comes back along with idle surging!!. So i am trying to gather the funds for a Microtech ...hoping this will fix the problem.
However, i did notice that a grounding wire had broken away from from my ecu. Regrounded that and also sprayed a battery terminal protection solution on any exposed connections. I also replaced the oxy sensor.
Now i find the acceleration is much smoother and hestitation is not present. However, every so often the cheeky b4$tard comes back along with idle surging!!. So i am trying to gather the funds for a Microtech ...hoping this will fix the problem.
11-13-03, 03:37 AM
#34
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I have a brand new 60Ah Banner Battery, i disassembled the ecu when socketed the eprom and cleaned all contacts and replaced every washer with corrugated type, cleaned and sprayed battery contacts and grounds (BTW can someone put a list of all grounds in order to check them all??) added grounds from battery to chassis and from intake manifold to firewall, repalced fuel filter with Mazda genuine (what a pain in the ***!!) NOTHING changed.
I noticed that the previous owner changed throttle body leverage, that may increase the hesitation i think
i will check also fuel pump and it's ground
do you think that changing fuel pump with that Nippondenso on RX7Store will help?
I noticed that the previous owner changed throttle body leverage, that may increase the hesitation i think
i will check also fuel pump and it's ground
do you think that changing fuel pump with that Nippondenso on RX7Store will help?
11-14-03, 09:31 AM
#35
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Originally posted by CapitanCombo
(BTW can someone put a list of all grounds in order to check them all??)
(BTW can someone put a list of all grounds in order to check them all??)
Grounds to check:
1. The two black ground wires that run from the ECU harness to the ECU
mounting bracket. Move these wires directly to the vehicle chassis. (bottom
10mm bolt through ECU mount)
2. Fuse panel to vehicle chassis. (next to the drivers left leg there is a
ground point. Doesn't require replacement, just sand & apply Dielectric
grease)
3. Upper intake plenum to firewall.
4. Battery to vehicle chassis.
5. Engine to vehicle chassis. This is where you use a 14mm bolt in the
Pettit kit and bypass the metal plate.
6. The braided strap that runs from the bottom of the floor pan to the main
cat/catback connection (under the rear passenger side aluminum pan).
7. There's one that bolts to the rack that holds the solenoids to the rotor housing.
8. Also one down on the driver's side of the motor above the oil level sender.
Maybe others can contribute some that I've missed.
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