Ok, I got my 94 HG job done and everything is good. Now it is time to resolve rough warm idle on my other truck, a 93 2wd 22re. Symptoms are starts and idles fine cold, very low and rough idle warm, almost stalls at idle warm. Give it gas it runs fine. I started looking at my egr system, vacuum etc. Sprayed carb cleaner where egr bolts to back of air chamber and got a very slight rise in idle so must have a very slight leak there and intend to change this gasket. No other vacuum leaks found. I tried pulling vacuum lines from EGR and blocking them. I found no vacuum on any lines at EGR when checked at warm idle. Should this be the case? Thanks

 

you sounds just like me. my 94 22re runs beautiful when i first crank it up but after it runs and warms up it starts to idle low, so hopefully someone can answer us both

 

Ok, I did find that the slight leak where the EGR Pipe bolts to air Plenum was simply a loose bolt. Tightened it and no more leak. It did not have any effect on the rough low idle though...still searching

 

Hard to say from this distance, but if the timing is a bit retarded it can cause a slightly low idle speed.

 

but if it was timing it would do it from the start, not just cause it got warm. It runs good when you first start it but when it gets warm it idle lower and lower.

 

Have you adjusted your idle screw? can you get it to idle at 750rpm?

 

Maybe. You have a fast idle until the engine warms up. Could be that the fast idle is a little low too, just not low enough to be readily apparent.

Could be a lot of things, but timing is easy to check and besides, I've got it on the brain.

However, with the EFI engines and ECUs setting the timing, once it's set, it shouldn't change. That is, the distributor's not going to rotate itself and there aren't any points to wear out and the dwell won't change. So, if the timing was set properly some time in the past, and nobody's messed with it, somewhere else is the place to look. Maybe I should replace the part of my brain that's currently obsessed with timing with a part that's obsessed with the TPS or something. Or maybe just thoroughly cleaning the TB.

About the EGR, Here's the link to the EGR page from the 93 FSM:http://personal.utulsa.edu/~nathan-b...18egrsyste.pdf

 

You set the idle when the engines warmed up. It doesn't matter a rat's arse how it runs cold as long as it runs properly warm. You fix the cold issues (if there are any after fixing the idle) after everything else is fixed.

If it idles bad when warmed up... get it idling properly when warmed up.

Come back if you have cold idle issues.

 

Sorry, don't mean to sound so terse and mad.

 

I have been searching for answers for my rough idle for months. Just found out today that the tube from the Plenum down to the Air Valve had a huge crack down at the air valve out of sight and was letting large amount of air through. I have fixed it temporarily with correct dia tubing that I had but it's not pre bent.

Here are things it wasn't caused by but I wasted time on them anyway:
Ign timing
TPS
EGR
Spark Plugs
AFM
Valve Timing
Knock Sensor (relocated it)


It now idles nice and smoth at 750 RPM just like Abe always says they are supposed to.

 

A picture to show severety:

 

Thanks for the input...the problem continues. I haven't had time to chase it more yet. The plenum appears to be pretty clean and the truck runs great, except at idle. I adjusted the idle screw but this is not the issue. I continued to check for vacuum leaks and so far have found no others.

 

Pull the plug on the TPS while it is idling roughly, if that fixes it, follow the TPS adjustment procedure on the following link EXACTLY!

http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

I finally fixed my rough idle problem, exact symptoms as you. I couldn't figure it out because I thought I adjusted the TPS correctly. I followed the steps in the above link exactly, and now my truck idles perfectly, and feels 100% better to drive!

 

I guess the '93 doesn't have the same Air Valve setup as my '88. I had a '94 up until 2002, but can't remember dealing with these issues on it. Here is a link to FSM for your type Air Valve. http://www.ncttora.com/fsm/1993/engine/35auxiliar.pdf

Have you already inspected the tube from the Air Box to the Throttle Body. It's pretty common to have leaks there that cause rough idle.

Good Luck. Mine is running like a champ since I bought and installed the two hoses that run to the Air Valve.