I have another thread in the TBI section of this board that has been going on for the past year+. It is in regard to a high idle problem I am experiencing and, for the life of me, can not figure out what is causing it and how to fix it. I ask you to please read the thread, I know it is somewhat long (30 replies that are decent in length), but I don't think I can correctly sum up the information presented there into a new question without leaving out key details.

https://www.thirdgen.org/forums/tbi/...ng-issues.html

Thank you, I do appreciate any and all help I can get.

 

I'm no expert, but I have a few things you can try.

First, you never said how you checked for vacuum leaks. I would get one of those propane torches (used for plumbing). Turn on the gas a little and go around the TB, all connections to the TB and the TB around the heads on a cool engine. If the idle gets higher, you have a leak. Be sure to check all around the TB since there are a lot of opportunities for leaks to occur.

I had a problem just 6 months ago with my throttle sticking open enough to cause a high idle. I know you said you checked it and say it doesn't close any further, but you might want to check that again. I had two problems that I think contributed to my symptoms. I pulled the throttle body off and
saw that the blades were ever-so-slightly rubbing the bores. I removed the blades (since they were going to need adjustment anyway) and found that the shaft was very dry and didn't feel smooth like I thought it should. I completely removed the shaft and put a thin layer of sylglide lube on it and carefully reassembled it. Sylglide stays put and won't run out like other greases, so try to find some if you can. After that was done, the throttle opened and closed very smoothly. Now, with the throttle body still off, I shined a flashlight from underneath and centered the blades perfectly so there is no binding at all. While you are there, double check that the idle screw is backed out so that it isn't touching the throttle stop. Doing this completely solved my high-idle problem

I would do a search about finding minimum idle air requirements and follow the proper procedure about finding the correct spot for the idle screw adjustment. Then after you do that, recheck your TPS voltage. It should be at about .55 volts at idle. This is an important step as I'm sure you are aware.

You'll also need to do a search on resetting the IAC, though yours is already set correctly at around 10 counts at idle. However, if the IAC reported 0 counts and it wasn't completely seated, it's not really 0 counts, is it? The ECM wouldn't know that if it's given incorrect information.

That's all I have for now. Like I said, I'm no professional but have some experiences. Hopefully it helps you.

 

All right, I will definitely check into resetting the IAC and the slyglide.

As far as checking vacuum, initially I removed the vacuum lines from the car, turned the regulator on the air compressor down to around 10 or so PSI and then filled a bucket full of water. I caped one end of the hose with my thumb, and forced air into the other end and submerged the entire hose. I only found two small hoses that had ever so slightly small leaks in them, so I replaced them. Then a few weeks ago in my auto lab at my college I got a hold of a vacuum pump and used that to double check all my findings. That is how I found out the one going into the passenger compartment for the vents was not holding.

I properly set the idle screw using a Motus scanner in class. I followed the directions in my service manual. It states to set the IAC at 0 counts, disconnect the EST, then turn the idle down to around 475 plus or minus 25. I used the rpm gauge in the scanner so I knew it was accurate (as opposed to trying to rely on the tach in the car). I wound up setting it at 500. It then states to reconnect everything and reset the IAC I believe. I am sure I reset it then, but I will go ahead and try resetting it. I never did set the IAC to 0 counts the way they stated. Before correctly setting the idle the IAC was showing 0 counts, so I just left it at that before doing the idle adjustment. Afterwards was when I got the 10-12 counts at idle for the IAC.

Oh, also, the blades aren't scraping the bores. They migth be touching, but nothing to bind it up. I have tried forcing the blades shut more, but I can't do to the idle screw preventing the blades from shutting any further. Now, before when I messed with that idle screw, the throttle blades would get caught up in the bore and really stick. But I don't have that problem anymore.

However, what you are saying about centering the blades does make sense. Almost like over time the throttle shaft could have wallered a bigger hole and slightly shifted, and you re-centering the blades is just compensating for that. Next time I get a chance I'll try to pull the TB out and mess w/the blades.

 

You know that if you turn that screw at all you have to reset the IAC and TPS right? Otherwise the ECM thinks you are on the throttle.

 

I don't see how you can reset the TPS. The TPS has no movement on where it is mounted, it is a fixed position. It just sends different voltages to the ECU depending on where the throttle is. Also, I had read that if the voltage is within a certain range upon startup, the ECU makes that voltage closed throttle.

As far as the IAC, yea, I know I have to reset it.

 

TPS can be adjusted by sloting the holes if necessary.

 

Yes, if necessary. But Pre-Tuner is talking about resetting it. I don't get how that would even be done.

 

Well, you reset the tps by moving it to get the proper
voltage out.

 

Yes, that's what I meant. The range the ECM needs to see for closed throttle is between .55-.65 volts if I remember correctly. It doesn't take much movement to go outside of that.