So recently I have been going through and restoring a handful of sensors and such. I just not too long ago replaced both the IAC and TPS sensors (which yes, my car was running fine before but I wanted to update to newer sensors for the hell of it. Anyways...). I was driving afterwords and noticed that after an initial start and idle, any time I would drive and take it out of gear, or when idling, the car stays at around 1700-2000rpm. I figured it was the TPS, however I've gone through 2 of them and switched to the stock one again, and am still having the problem. Now when I changed the IAC, one of the bolts did break off, however I didn't think it was much of a concern because it still seems tightly secure by the other fastener. But does anyone have any idea what my problem may be? The car seems to run better with the new IAC valve, but could that be faulty and causing it to run like that?
-NOTE- When my car idles high like that, I shut it off and turn it back on and it idles where it normally does (900-1000rpm).

 

Have run though the IAC homing operations? Check your manual for the process as they can vary slightly bases on engine model. Certainly sound like your IAC thinks it closed and its not.

TPS causing high Idle RPMs does not sound possible on a drive by cable car. Any time you have high RPMs the engine is getting air from someplace. Either a vacuum leak or past the IAC motor. A TPS sensor can tell the PCM that the throttle is open and it may try to close the IAC (a stalling issue) but the TPS can not tell the PCM the throttle is more then closed so it should ignore the RPMs and add more air.

Changing sensors as a preventive process is a mistake. There is a much greater chance your wiring harness will become an issue in the near future then then the sensor itself. Going through a un-needed uninstall and reinstall of sensors is going to cause you more problems in the future then it will advert. Now if you are swapping in a new wiring harness then have at it. When it comes to 20+ year old wiring harnesses if it aint broke don't fix it.

 

I get that. So long story short, it's either occasionally having a vaccume leak from where the bolt broke on the top to mount it (yes, I'm an idiot for messing with it in the first place), or it's a **** valve from, well not to put any company's on blast but rhymes with mottozone. I'm going to try to re-install the original one, after cleaning the carbon residue off it. Hopefully it'll fix the problem.
On a side note, does restarting the car, which temporarily fixes the issue, have anything to do with it? Thanks for the response.

 

Have you done the homing procedure for the IAC motor? Honestly I am not sure how a car reacts over time if the IAC motor does not know its home position because step one after installing the working IAC is to home it. It will eventually re-home it self but that can take awhile.

Something like:
1. Remove battery power for one (1) minute. Restore battery power and place air conditioning controls (if equipped) in the "off" position.

2. Firmly apply the parking brake and block the drive wheels. Start the engine, shift the transmission to drive for automatics and neutral for manuals.

3. Allow the engine to run until the engine cooling fan has cycled once, or a maximum of 10 minutes.

4. Turn the ignition key to the "off" position for at least 5 seconds.

5. Repeat Step 2.

6. Allow the engine to run for at least five (5) minutes.


The correct IACV values for proper idle control will now be stored.

Its always best to check a manual for your car.

 

So quick update:
After doing the housing procedure for the IAC, the car seems to run better. However the problem I'm having is still occasionally happening, more after I've been in gear for a good 10 minutes driving on the HW, and when I come to a stop and shift out of gear it does it. It's to the point where it doesn't bother me much anymore or is much of a concern now, however being the way I am, I'd like to try to get to the bottom of it and fix it fully.
When I removed the old valve, there was a considerable amount of carbon buildup, and I wiped as much of it as I could out. Do you think some might have gotten lodged in one of the air passageways?
-thank you so much for all your help so far Gorn.

 

Yes depending on how you cleaned the port you have cause some issues. There are several how to clean the IAC/throttle body port videos on youtube. You should not have to rehome the IAC just because you remove it. Just DONT power the key on with the IAC connected and out of its port. You will be starting all over again if you do.