JGibson

So, I have the high idle problem that I have seen and read about all over the internet…I have done everything that has been discussed and still no change, actually it has gotten worse. Any other ideas on what it could be? Timing maybe? Probably the only thing I have not checked other than the computer itself…

cruiser54

Make sure your intake manifold bolts are snug and check for vacuum leaks at fittings and hoses around the intake manifold.

Have you ever cleaned the throttle body and Idle Air Controller?

Roler

It might be helpful to list what you have done so far

cruiser54

Well, there's that too...................

JGibson

Checked every vacuum that I could see (Not sure if there's some hiding), changed the Map, TPS, IAC sensors (Not with new, but ones I know are working), cleaned the throttle body, IAC and every ground I could find. I did find that the housing where the IAC mounts is missing a bolt that holds it to the TB and I can also see that some gasket is missing, I haven't taken it off yet but I did spray Carb cleaner around/on it with no change so I figured it was ok. I've unplugged all of these sensors (One at a time and all at once) and they all seem to be working because they change the way the engine runs in some way. I have not tested any of the voltage coming out of any of the sensors but I did test to see if there was power coming through, all was fine. I have never had to use an OHM meter so I'm lost there towards checking the voltage coming through them. My son and I tried closing off the hole inside of the throttle body where the IAC is and it idled down to normal...as far as driving, no idea cause he used his fingers to block it off. Is there anything I may have missed? A vacuum line that is hidden, a ground, another sensor? The codes I get from the check engine are 12, 14, 21, 34 I've looked these up so I know what they are just not sure what to do about them and if they are responsible for the high idle...any help, criticism, idiot jokes are welcomed, I'm at a loss and very close to just getting rid of the Jeep...HELP! LOL

bluejeep2001

Idle speed or any engine run speed is determined on how much air goes past the throttle plate...the engine doesn't care where this air comes from. How high is your idle.? First make sure your throttle plate is closed and the cable linkages are all at the stops. Do you have cc. Disconnect that cable from throttle linkages. What happens to the idle speed if you turn on the ac and the lights and blower fan and defroster to load it down?. The iac is opened and closed by pcm to maintain 700 ish speed at all idle conditions. When the iac opens more air is allowed to pass around throttle plate and your speed goes up

exasemech

Tracking down the Map sensor error (14) would probably be a good idea. Start with looking for any sort of leaks or wiring/connector issues

cruiser54

IAC isn't sealed up? Intake bolts checked?

Roler

( I'm 97+ so a disclaimer- but there is a map sensor and vacuum systen code. Both can influence rpms)

Ok- assuming that your cracked housing AND missing gasket STILL don't allow for air to be sucked in, what you mentioned above is a clue.

It implies that if you take the IAC air out of the equation (blocking its hole), your idle returns to normal.
You disconnected the IAC and noticed a change in running (correct?): high or low?
If your IAC (which you said was not new but working and cleaned) is indeed working as it should, it behaves like it's opening more than it should at idle. That, or you're having such an amount of 'false' air, enough to keep it running at idle without the IAC (which you likely would have found when checked for leaks)

So, I'd be curious what the IAC sensor voltage is at this stage and what the TPS voltage is at idle.

JGibson

So this is what I did and got the idle down to about 900, I removed the IAC (again) and took it apart, cleaned everything I could get to, greased it but when I put it back together I did not screw it down to where it was when I took it out. This tells me that the IAC for some reason is not working (neither is the other two I tried). I used a test light to find out that the wiring for it DOES has power with key off (4 Prongs) 2 hot and two not, Key on, same thing, running, 3 are steady on and one pulsates every 2-3 seconds (still no ohm meter). I can also force the linkage on the side down a little to get it down to around 800. Only thing is, it does not idle up at start like I would expect it to do, it just starts at idle, no revving.

Roler

Does the 93 have the cable adjuster?

cruiser54

For the TV cable?

I'm thinking there is something wrong in the linkage and all this IAC work is some kind of band-aid "solution".

Roler

Yep

JGibson

Replaced the iac and hooked up the electric fan to a toggle switch, rode yesterday for more than 6 hours with no problems at all, not sure which one fixed the problem but it’s working great now 👍. Thank you all for the help and support.

Roler

Probably the IAC 😉

Thanks for letting the forum know about the outcome - we might actually have some closure in a thread 😊