twan

iTrader: (2)

Hey guy's, I've been searching for an answer to my problem forever so I'm gonna ask For your help. Iv got a modded /street ported rebuild with stock ecu and almost no miles on the motor. Got her to start up and idle great with a readjusted TPS and simplified seq for no other issues. Did block off plates mod so only ISC, Fuel thermo, IAT, and coolant temp sensor in the filler housing is functional. When shes cold, she drives. Meaning I can drive her around the block a couple times. but as soon as shes warm with vacuum at 17hg and Fuel pressure at 38 psi, I don't loose my idle at all but shes completely undriveable. I can give her gas but I get nowhere near enough power to drive her at all. I have to rev her almost 2 to 3 times higher than normal and slowly ease off the clutch to move at all. Actually feels like the clutch is majorly slipping. but it's brand new!!! I guess some might call this boging. I'm thinking, since I still have the stock IAT in the Stock location, Its failing due to heat soak or age but I have no codes at all. When this happens, I have to wait about 20 to 30 minutes before I can drive her again. Does this even sound plausable regarding this sensor? I read somewhere that it could cause a rich condition. To me, that means my air mixture, after warmup, when I give it gas, is completely off resulting in no power and really poor fuel mileage. Another issue I seem to be having. Other wise, what other sensors come online, regarding the ecu, after warmup if the iat isn't the culprit?
Does anybody have a flow chart regarding the ecu and sensor process for cold to warm operation?
H E L P ! ! !

kensin

iTrader: (22)

When th stock iat goes nuts. Meaning read -numbers. It runs rich and idles really bad. When it's not reading at all I don't know what it does then. Just from my experience .

twan

iTrader: (2)

Yea, thats my issue. I need to know when it's actually read by the ecu to influence the injectors. I'm probably incorrect but I thought it wasn't read until the ecu was in closed loop. Meaning after warmup. Bottom line is that something that doesnt "Matter" to the ecu when the engine is cold, it is causing either a rich condition or a lean condition which, i believe, is causing my no power issue once the loop mode switches Possible suspects are, coolant thermo sensor, o2 sensor, ISC, the fuel thermo sensor, or the IAT. The iat is currently my primary suspect!

scotty305

iTrader: (2)

I don't know the exact AIT fuel correction used by the stock ECU, but my gut feeling says the air temp sensor doesn't have enough influence on fueling to cause that much of a problem. If it is reading abnormally high or low it may cause the ECU to pull ignition timing to the point that the engine lacks power.

Try disconnecting the air temp sensor plug when the car is warm, this will probably put the stock ECU into limp mode but if the engine runs better that may be a sign that the AIT sensor was your problem.


Personally I'd suspect the coolant temp sensor or O2 sensor. Coolant temperature tends to have a pretty large influence on fueling, and it is possible to connect the coolant sensor plug to the fuel temperature sensor and vice versa. One way to double-check this is to look at the wire colors compared to what the factory wiring diagram indicates. Another would be to use a multimeter and check for continuity between the sensor plug and coolant input pin at the ECU.

Again I'm not sure exactly what the stock ECU does with the O2 sensor, but if you disconnect it the car should run in a limp mode.


Unfortunately you're sort of flying blind, without a wideband AFR gauge and/or a timing light you can't do much aside from disconnect things or swap out parts.

kensin

iTrader: (22)

Borrow a PFC or buy mine. Lol.

eViLRotor

iTrader: (2)

The AIT sensor is read by the ECU at all times.
According to the FSM, it affects the injection amount, ISC and ignition.

Also, the failsafe is 20C (68F) intake temp. So, when it fails it will compensate quite rich.

Mahjik

iTrader: (1)

Did you verify that you have the correct connector on the fuel thermosensor and the coolant thermosensor? They are the exact same connector type (same sensors just different locations) so they can be easily mixed up.

twan

iTrader: (2)

Regarding the coolant and fuel thermosensor connectors, im pretty sure they are in there correct position but at this point im double checking everything twice, so i'll just switch them to see if there is any difference in performance. I also built a 4 led flash set to confirm the injector pulses. Especially the secondary injectors. I'm gonna pull the connector off the IAT to test as recommended but wont limp mode cause the same drivbility problem? BTW, good idea about checkin the continuity at the ecu. Never even considered that.
Might be interested in the pfc in the near future but for now, gotta get her running on the stock ecu before I try to calibrate to the pfc. And i'm negotiating on a LC1 wideband but until I get it; flyin blind is right, Im smackin into trees left and right. ASAP, i'm gonna build that data interface for the stock ecu that i found in here so I can watch all the ecu data in realtime.
https://www.rx7club.com/showthread.p...data+interface

twan

iTrader: (2)

ok, I have almost finished the led indicators but half way thru, I've noticed that my secondaries aren't coming online. Yea, I was running the engine while I was making the LED wire connections. I do have the elbow off so no boost is being seen at the TB but on 2nd thought, Should that even matter? They should be coming on either way!! Correct me if I'm wrong. And It looks like the thermo sensor connectors are correct and IAT caused a CEL when I disconnected it but didn't change the drivability issue. I'm betting it's the secondaries. Their not getting pulse! why? Gonna hit the source. Yep!! The ECU!!

twan

iTrader: (2)

Before I Went to the ecu, I went directly to the plug, Seems that with car on/ engine Off, I have voltage to the injectors. Well the front secondary. For some reason though, with the engine running, the led isnt flashing when I open the throttle by way of the cable under the hood. I know I have the polarity correct and the primaries have voltage with the car on/ engine off. What tells the injectors to pulse, or better yet, What tells the Ecu to pulse them?

twan

iTrader: (2)

Oh well, The FSM actually says that my secondary injectors should only come online after the primaries hit 40% and better. AKA when boosting. SO I take that to mean maybe my pressure sensor may be acting up. I don't know, Something is wrong. gotta get to the ecu and check for contunity on fuel and water thermo sensors, and injectors but for now, Screw it, I'm calling it a day. back at it tomorrow. ****, it's 10:30!!!

twan

iTrader: (2)

bump

wstrohm

This may not be relevant, but our '94 (108K+ miles) just started idling roughly and at a lower speed than normal when warm, and simultaneously threw a Code #11. So I ordered a new IAT sensor from Ray Crowe and will install it when it arrives. I don't think this was a coincidence.

kensin

iTrader: (22)

My problem was with the wiring harness. Changing the iat sensor will not help

twan

iTrader: (2)

i'm just gonna wait till i build thie data interface so i can see what is happening in the ecu. Hopefully i'll be able to see and fix the actual issue causing the prob. And i'm gonna do the IAT mod where mine will be in the existing elbow port where the fast warmup hose goes. Did the blockoff plate mod so i dont need it. All except the OMP and ISC or ICS (idle control Solenoid) wonder if that sticking closed or open might cause my symptoms. Hey, watcha think on that one?

twan

iTrader: (2)

The cel is not on but I found two codes in the ecu 30 and 40. 30 is Split air bypass. 40 is purge control. Im wondering if the Purge solenoid is stuck which is causineg a lean condition in the engine. Or maybe it's causing a rich condition by being stuck open. Not sure which but it's defititely throwing a code. The split air code, #30 will be fixed but I don't think that coule be causing my no power problem. I do know that when I take off the fuel cap i get a loud air bleed-off sound for a few seconds. Not sure if it's vacuum or pressure in the tank. Would either of these two codes cause limp mode but no CEL?