guess on malfunctioning part

[Jonn]

91 LUm. 2.5
Car has new plugs wires and coils. Has new map/iac/Tps/coolant temp sensor/manifold air intake temp sensor/
have cleaned the Throttle body and put in a new fuel pressure regulator/
Only parts i "know" that need replaced is the EGR valve, it reciently got a bad diaphram. It "IS" sealed. hose disconnected and plugged. If i lift the diaphram, engine misses and trys to die as it should. So there shouldnt be any Vac leak there. I have also checked the MAP hose.

Before the TPS, car would start to what seemed like miss on one cylinder when you were at about 3/4 on steep hiway hills, that has been cured with TPS.(only on 3d gear pulls)
Now it is acting up in a different way, when starting cold, you have to hold the throttle open a little even with a good IAC, soon as it starts, it will run on its own. But as it warms up, fast idle will not so much fluctuate, but sound like you quickly turned the key off and back on
And also it will sound on and off during warm up like you pulled a plug wire off for a few seconds and reconnected it again, over and over.

Does this a few times till it warms up, then when warm, idle will not go down to normal untill you decend a steap hill in low gear, get to the bottom idle will be perfect, once you give it gas and stop again, idle will be high again.
BUT, last night after it was warm, out on the road, about 1/4 throttle, it would do the "turn key off and back on quickly" thing, also spit and pop/backfire, in between it would run fine, then miss, run fine, miss, run fine.... I stoped and sit and gave it gas in neutral, it would be smooth, miss, backfire, smooth, over and over. I let it sit and run while wife was in store, we started home, it didnt miss once all the way home, ran fine.
Im am leaning toward ECM/ICM/crank sensor. BUT only thing that dont make sense to me is how it can run fine for miles, then act up so bad.
ALSO, during ALL these problems, full throttle is ALWYS fine, floor it anytime and it will run just fine up or down hill, no problems at all.
I can live with the high idle, but the missing/popping/backfire has got to go. ANyone? and to anyone who helps, thanks..

[jeffcoslacker]

Have you ever tried doing the PCM reset procedure, just for laughs, and see if anything changes? If it does, even temporarily, that could be helpful in trying to sort it out.

[Jonn]

Originally Posted by jeffcoslacker

Have you ever tried doing the PCM reset procedure, just for laughs, and see if anything changes? If it does, even temporarily, that could be helpful in trying to sort it out.

What exactly do u mean a pcm reset? If you mean disconnected battery, yes. Or is there anoter way?

[jeffcoslacker]

No. Not that I know of, really. Just wondered if it had learned a bad strategy that it couldn't get out of after all the new parts. Is that the TBI version? If so, check your connections/grounds to the injectors. Move the wires around slightly as it runs. I'm almost wondering, if your dealing with a wiring sag kinda problem, where something is intermittantly touching something hot or grounded that it shoudn't be. I'd suggest try letting it idle, and move/twist on every bit of wiring you see, and see if it stumbles. pull every sensor pigtail apart and reconnect them. Pull the main harness connectors apart and check for moisture or corrosion. Spray some WD-40 into each one as you go.

I've solved a lot of phantom problems doing this.

It has been said that up to 90% of all performance issues on feedback controlled cars stem from bad connections and grounds.

[Jonn]

Originally Posted by jeffcoslacker

No. Not that I know of, really. Just wondered if it had learned a bad strategy that it couldn't get out of after all the new parts. Is that the TBI version? If so, check your connections/grounds to the injectors. Move the wires around slightly as it runs. I'm almost wondering, if your dealing with a wiring sag kinda problem, where something is intermittantly touching something hot or grounded that it shoudn't be. I'd suggest try letting it idle, and move/twist on every bit of wiring you see, and see if it stumbles. pull every sensor pigtail apart and reconnect them. Pull the main harness connectors apart and check for moisture or corrosion. Spray some WD-40 into each one as you go.

I've solved a lot of phantom problems doing this.

It has been said that up to 90% of all performance issues on feedback controlled cars stem from bad connections and grounds.

Well, i finally got all the stumble, cough, spit, backfire, high idle stuff fixed. All it took was a new crank pos. sensor and a new Ign. control mod. In all my searching online and books i have not once saw anyone say that a ICM had anything to do with idle air control, but apparently it does. Crank sensor had cracks around it, looked like plastic fatigue from heat/cold/age. Im not sure if it was "totally" bad or not, but it was cheap enough to replace. ICm on other hand was 80.00
Running fine now, smoother than it ever was. Oh, by the way, its 91 2.5 TBI engine with DIS Ign.
I also used heat transfer compound between the IDM and its alumium heatsink, none provided with new ICM though, cheap A***
thanks for the replies, yours and the other hundered's of posts i have read about stuff like this helped make the decision to buy those parts.