I have a '97 LT1 with A4 tranny. Well, here's what I did this past week...
--new entire opti distributor
--160 deg. T-stat
--Removed Donkey Dong
--replaced PCV hose
--new water pump

Yesterday, while checking everything at idle, the engine ran really smooth and normal at 800RPM.
Today, it idles steady at 2200 RPM. Even after revving the engine a couple times, it still doesn't drop below 2000RPM.

What prompted me to do everything was a code I got indicating random misfire associated with a very noticeable smell of unburnt fuel and that smoke you see with a rich or unburnt fuel condition. I have a set of injectors coming in the mail, but I wanted to see if I had the Opti in correctly, and it started right up without a single miss...in fact, the misfire code disappeared!

I double checked all the vacuum hose the best I could and everything was hooked up correctly and seemingly nice & tight too.

I wonder if an injector or 2 that is stuck partially open is dumping a higher amount of fuel making the engine run at the high RPM, but not too much fuel to cause a miss or throw a code. What gets me is that a couple "bad" injectors should be indicated by a rough or surging idle right? This engine runs very steady at 2200 RPM.

Any thoughts or suggestions?

 

Id check for vacuum leaks , if none are found then Id close the throttle blade stop screw a little bit , BUT FIRST Id check whatever you used to close the donkey dong hole cuz it might have come undone or fell out.

 

The "Pert plug" is tight on the elbow. I used an epoxy and made sure it sealed all the way around the entire cap.

Where do I find the throttle blade stop screw? I do see what looks like the tip of a crew where the throttle cable attaches to the TB, this acts as the stop for the cable, but there's no way to access the head of this screw.

 

yeah you can its in that round cavern behind the tip of the skrew , I think it was a t-30 torx bit. I used the torx bit and a mini locking plier to turn it . left closes the blades and of course right opens them . do this with the car running and see if it brings the idle down , beware tho if you have a vacuum leak and this works then your just covering up the problem

 

IF you didn't touch that scrwe theres no reason for it to go that far out of adjustment. I would look for a vaccum leak especially around that PCV valve.

If not that, then I would think it would be a bad IAC valve.

 

Problem Fixed!!!!

Well, I surprised myself! WHile reading through the Chilton's manual, I came across the section about "Idle Learn Procedure"....I had forgot to mention in my original post that I always disconnect the battery for safety when working on the car (except when I need something running).
Chilton's stated that whenever the PCM loses power, the control module's learned position of the IAC valve pintle is lost. Thus, the PCM was searching for an idle speed I guess and decided on the 2200RPM.

I re-learned the PCM and now my baby runs smoother than when I first bought her!
Free fix that took only 30 minutes (due to the stages of letting the car idle)!!!

 

So all you had to do was let your car idle?

 

Yep..There's a specific procedure for re-learning the PCM's idle control module, according to the Chilton's manual. It work perfectly for me. Here it is:


You will need a couple of wheel chocks. Chock the front of both rear tires to prevent the car from moving forward.

-- Turn OFF the AC. Apply the parking brake and start the engine.
-- (For safety, apply pressure to the brake pedal) Put the car in DRIVE. the car will obviously try to move forward. Slowly ease off the foot brake until you are certain the car will not move forward. (My car didn't move at all, but I still sat in the car and had my foot near the brake pedal just in case.)
-- Let car idle for 8-10 minutes (manual says 10 minutes, but my car worked using 8 minutes) while in DRIVE. The idle should drop down to around 800-1000 RPM.
-- WHile still in DRIVE, turn on the AC and let idle for another 8-10 minutes.
-- Put the car in PARK with AC running, let run for 8-10 minutes (here I noticed the RPM returned to normal 800)
-- Turn OFF AC and leave in PARK with engine running for another 8-10 minutes.

-- Turn engine off for at least 30 seconds.

VIOLA!!!! Idle speed corrected!