1993 Loyale, 5 speed , EA82 SPFI

Vehicle does not idle smoothly. Engine speed will fluctuate +/- 500 RPM at idle. It also seems to occasionally misfire while cruising. There has been no check engine light, and no codes until I replaced the wiring harness (see below).

Around 6 weeks ago, the car would stall when ever I stopped. This continued for about 25 minutes, and then suddenly started working fine. Same problem occurred about 4 days later, and started working normally later that day.

November 27th, I replaced the leaking power-steering pump, and while I was at it, removed and cleaned the idle air control valve and replaced the connector at the wiring harness. Vehicle has been running great until December 9th.

Last weekend, I replaced all four spark plugs, re-examined the IAC valve, and checked the mass airflow sensor and the TPS. These components seem to be working within parameters.

This may be a “red-hearing”, but I have noticed that if I “jiggle” the wires leading to the MAF sensor, the engine will either “smooth out” for a few seconds, or it will stall. But I can’t do this with any consistency.

I have tightened the tension on the throttle cable to temporarily increase the idle speed to make the car “drivable” until this problem can be diagnosed.

I took the car to my local dealer. The mechanic apparently found that “the IAC circuit was open”, indicating a short and recommended replacing the wiring harness. I purchased and installed a new wiring harness and a new IAC valve, but the problem continues, and new problem has occurred.

The new wiring harness was apparently for a “California” car, and had a plug for an EGR temp. sensor. Now I’m getting a code 55 (EGR temp sensor). Is there any way I can just jumper this plug, or should I pull the pins on the harness plug where it attaches to the main bus?

Does anybody have any ideas as to what could be causing my idling / stalling problems?

Edited December 25, 201015 yr by jimbo747
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Try moving the harness more. I had a wire fail in the engine harness on one of my cars some years ago. I eventually found it by using an ohm meter while flexing the harness to narrow down where the break was.

I replaced the wiring harness with a brand-new one.

how about the engine temp sensor, the one on the thermostat withthe green plug and the 2 wires. the reading from this will affect the ecu's calibration of the IAC

Iac has nothing to do with fluctuating idle if you dont believe me unplug it and youll find out anyways I found out my injectors needed cleaned with mine but also what can do it is the mass airflow cleaner may need to be cleaned alittle spray from your auto parts store can help a whole lot.

 

other than that i have had issues with fluctuating fuel pumps lol

but to figure it out for yourself unplug sensors until it works normal.

 

Dont overthink things it only drives you crazy

Did you clean the MAF sensor? and check the wires to the coil.

I visually inspected the MAF sensor and it looked clean. I think I sprayed it with some electronics cleaner, but I will try that again. Also, I will look at the coil and distributor wiring. Thanks.

I've cleaned the MAF, and checked to wires to the coil. Coolant temp sensor is also giving specified readings. Everything seems to be as it should. I also replaced the TPS (that alone is a story for another thread). Anyway, I'm now thinking it could be:

 

O2 sensor

MAF sensor

Fuel Injector itself (this is an SPFI)

 

Any thoughts?

o2 has nothing to do with idle issues only driving issues maf sensor should only be cleaned with maf cleaner

o2 has nothing to do with idle issues only driving issues maf sensor should only be cleaned with maf cleaner

 

I had a almost plugged cat and this happened to my car

Solved the problem. After replacing the IAC, the TPS (needlessly -- that's a whole post in itself) and cleaning the MAF, I bought and installed a replacement FUEL INJECTOR!!!!! Started right up and is purring like a kitten.

 

Thanks for all the advice.