Has anyone actually figured out the rough idle?

[ReD-rAnGeR]

forgot injectors, did them too

 

[94twodoor]

I just bumped the rpms a tad to about 950rpm at idle. Took away the rough idle at stops. It was a simple set screw.

 

[dopey fudd]

I am having a very similar issue.

93 3.0. when the temps drop below 50 degrees, the truck starts right up. runs at around 2500 rpm, then as it starts to drop to regular idle, I get a check engine that flashes 3 times, the idle then drops to around 500 rpm, or dies, of its really cold out. then it spikes back up to 2500, and slowly decreases to standard idle, around 1000 rpm. I have checked the idle air sensor, and replaced the coolant temp switch. cannot pull the code from ecm, due to being a soft code. throttle body is clean, maf is clean ,but will clean to be safe.

I'm at a loss at this point. it did it last year in the fall- winter but stopped. started in the spring, and stopped, all summer long. started again in mid november. its getting worse, to the fact that if it dies now, I need to hold the throttle open to restart.

any help will be appreciated.

 

[CraKel]

Exact same problem here!! 94' 3.0L. Need to giver gas just to keep it started sometimes.. After driving 5km its all good though? Iv'e changed or checked everything you guys have already mentioned and have the 5.0L goin in soon so really Im not worried anymore but it would be nice to know what the actual problem was!

 

[basketranger]

sounds like a vacuum leak!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[jim cafarelli]

It was a burnt valve on my 2004...

 

[rurouni20xx]

vacuum leaks are the major cause of that deal, i had tons on my 93 truck, fixed them and she idles great. then the cat stopped up and had it removed, really lopes now from lack of exhaust pressure. as for the suggestion of moving the "idle stop screw" DO NOT TOUCH THAT!!! it is not an idle stop screw, that is the baseline stop for the throttle position sensor, you tamper with that and the computer on startup is going to think that 3-8% throttle is zero. this will really cause idle problems since the iacv will start hunting in warm weather (rpm fluctuation in warm weather).

 

[dopey fudd]

been a while...but there have been a few changes.

I put the original iac back on the truck at the biginning of the summer. it choked off just fine for a few days, no issues. I started it a few days later, after a rain shower. the truck went back to th old, "flash, stall, surg" after that happended, the truck failed to choke off again. this time, there was and has been no check engine flash, and absolutely NO choking of the engine. I have to keep my foot on the throttle until it warms up or else it either stalls, or lobes significantly. I am at this point looking as if the ecm has crapped out. Seeing how I have replaced everything prior to the ecm..basicaly everything that tells the ecm how much to tell the iac to close.

vacuume is ok, fuel pressure is ok, air intake is ok, spark is ok,