Intermittent High Idle?

[choinga]

After my MAF install, I reset my idle per manual (warm idle, jumper the DME test port, set idle with screw to 840) and haven't seen any major problems but I also haven't driven the car as much as I did today.

I ran a 40 mile errand with a little of that in stop-n-go traffic and hit a few lights. After driving on the freeway for about 15 miles I hit my first stoplight on the first leg of the trip and noticed that the idle had jumped to about 1200RPM. Rev'ing the engine wouldn't get it to settle back down. It only did that few other times (out of ~15 or so that I was at a light or otherwise idle for the trip) and I'm curious what that might be?

ICV maybe? I pulled the hoses off a while back and sprayed carb cleaner w/ compressed air behind it and finished it with a shot of WD40 to clean it out. TPS? I've got a new TPS I'm going to install when I pull the TB off to re-seal with the Arnworx kit.

Anywhere else to look?

Probably worth noting I have a weird what I call 'idle bomb' condition. Basically, at anything higher than about 3k RPM if I let of the gas and clutch the idle bombs to about 300-400RPM before catching and idling up to 850ish. This is very repeatable and the car doesn't have to be at boost to make this happen.

[voodooecon]

i have a very similar high-idle issue. It only manifests itself after the car is up to temperature, and usually only when its 75 degrees F outside. My idle can seemingly get stuck in the 2-3k rmp range after a stop. I replaced the ICV and it didnt make a difference.

I just bought a new TPS which i'll install soon. I also got a thermo-fan switch and coolant temperature sensor as it seems to be temperature related (for me anyway). I think i'm just going to install all of them and hope for the best. I hate the "throw parts at it" method, but they're cheap and I dont have enough time to diagnose everything - i'd rather rule things out.

i read somewhere (cant remember where now) that high idle at warmer temperatures is a sign of the TPS being bad, but I cant figure out why that would be. Does anyone know enough about the inner-workings of the sensor to explain that?

[V2Rocket_aka944]

unplug the ICV and see if the high idle continues; the bomb thing definitely sounds like TPS

[choinga]

I may drive around a bit tomorrow with it unplugged and see...

Interesting thing though...where does the hose that connects to the middle connection on the intake (not the hose to the ICV) go? I had my shop install an aftermarket hose there (one of those blue flexible ones) and I noticed that at pressure it pinches a little at the bend. If I pinch it all the way it dramatically affects the idle speed. Maybe that has something to do with it? Anyone know where that goes - and better yet a part number of the 'real' hose to replace that thing?

I went ahead and bought a new Bosch ICV and I already have a new TPS - just waiting to get a full day so I can take the intake off and get to all of this at once. It's really driving me nuts.

I'm guessing that either of these problems can affect AFR. As soon as I turn the car my WB drops down into the 12's at idle. Would a ICV going bad (or gone bad) have this effect as well?

[choinga]

I may drive around a bit tomorrow with it unplugged and see...

Interesting thing though...where does the hose that connects to the middle connection on the intake (not the hose to the ICV) go? I had my shop install an aftermarket hose there (one of those blue flexible ones) and I noticed that at pressure it pinches a little at the bend. If I pinch it all the way it dramatically affects the idle speed. Maybe that has something to do with it? Anyone know where that goes - and better yet a part number of the 'real' hose to replace that thing?

I went ahead and bought a new Bosch ICV and I already have a new TPS - just waiting to get a full day so I can take the intake off and get to all of this at once. It's really driving me nuts.

I'm guessing that either of these problems can affect AFR. As soon as I turn the car my WB drops down into the 12's at idle. Would a ICV going bad (or gone bad) have this effect as well?

[V2Rocket_aka944]

the ICV makes the car run rich to warm up; sometimes when they fail they make it run rich even while the car is already warm and can cause the idle to surge.

[choinga]

thanks guys - well, mine's getting replaced. I've got my IM off now and waiting on a new one from Paragon. Hopefully the combo of this getting replaced, a TB rebuild, a new TPS and replacing a few suspect hoses under the IM will get me back on track.

[Supernotch93]

Originally Posted by choinga

thanks guys - well, mine's getting replaced. I've got my IM off now and waiting on a new one from Paragon. Hopefully the combo of this getting replaced, a TB rebuild, a new TPS and replacing a few suspect hoses under the IM will get me back on track.

Did you ever find out the problem to this..?? I having the same problem with my 88 turbo, I have a new ICV installed and all vacuum lines are new and look good and tight, I'm running the Huntley MAF.. I cant get the car to idle below 1200!!!, No matter if its hot or cold, I try to adjust idle air control on the TB adjustment screw and the throttle stop bolt.. nothing lets me go below 1200 rpm, yes ICV is taken out of loop while setting the idle via B&C shorted on the tester, tried also blocking the ICV from the IC pipes as well to set idle and nothing, also when i drive around the hotter the car gets the more the idle wants to soar averaging around 2k. What the hell....Over!

[choinga]

mine was only interimittent so never had it where it was stuck at 1200RPM or higher. It would just appear after I had it set right...was weird.

Since then I took the intake off and gutted everything...did a venturi delete since I had added a Tial, replaced all the hoses, installed a brand new ICV, installed a brand new TPS and then bought the Arnworx throttle body rebuild kit and did that. When I put everything back together, it ran and idled perfect so not sure which one of those actually fixed the problem.