On my 1995 GXE I have been having high idle issues for a while. The car idles smooth, but it is idling too high. It idles around 1100. My IACV screw is all the way in and it still idles this high. I am not throwing any codes. Also when I come to a stop and clutch the car the idle will surge up to around 2k then drop, then surge and drop again. What causes this? I am guessing my IACV is bad, but would that throw a code? The surging idle started happening after I ported out my TB and intake plenum neck. I did the plenum while it was on the car with a rag stuffed in the neck to block shavings from going down the tube. I figured I just got my IACV dirty, so I cleaned it but that did not change anything. Any ideas? Its pretty annoying. Thanks for any help.

 

Sounds like a lil air is getting in through the throttle body since you said you ported it? Did it completely port it including the part that the butterfly valve sits on?

Theres a screw on the TB, I dont know if you have messed with it, or it comes slightly open from factory, but maybe closing it a little more can lower the idle.

 

I did not take the butterfly out. I used a flapper wheel so I really do not know how I could have ported where it is suposed to be. I do have another throttle body so I could always swap them to see if that is the problem...the only problem with that is that the tps hook ups are different. On my 95 it a one plug set up, and on my other throttle bodies its a two plug set up.

Also what screw? I never knew there was an idle adjustment screw on the TB. The screw on the IACV is all the way screwed in.

If my TB gasket was leaking or if I had a leak anywhere past the maf I think the car would run like crap. The car is running fine, I just ran it in the 1/4 mile last weekend and had some pretty decent times so i doubt its that.

Could I have clogged the PCV valve with my porting job? I doubt it, but worth asking.

 

Theres a screw that pushes that butterfly valve open, its pretty small.. Here's a pic of my extra TB...



I doubt you clogged your PCV Valve..

Since you said it happend after the porting job, it has to be something related, so I dont THINK the IACV is malfunctioning..

 

My idle was high even before I did the porting, but the surging happed after the port job.

that screw pushes the butterfly open? I'll have to check that out.

 

Oh, high idle from before I see now hmmm...

Surging could be cause of a vacuum leak correct? Did you replace the TB gasket? Your running the stock TB and USIM right?

I know when I removed my TB off my old USIM that paper gasket was toasted, but when I put it back I never replaced the gasket and it never had a problem... I really dont know how it didnt leak because most of the gasket was gone.

Im sort of out of ideas right now, let me know if you figure anything out.

 

yeah, its the stock tb on the usim

 

when i had this problem with my car it was the 02 senors that were fried and needed to be changed.After i changed the burnt out o2 the car idle fine again.

 

My front two 02 sensors are brand new. I am however throwing a code for the rear sensor. But my understanding of the rear sensor is that it only moniters the cat, and does not affect how the car runs (I could be wrong).

 

My rear o2 sensor has been out since i've bought the car, never had any idle issues.

 

bump it up.

I'm having the same problem now. It was idling perfect at 700rpm today, and all of a sudden it started idling at a solid 1500. I played with the IACV screw and screwed it all the way in but it still idles high at 1100....wtf? Did you ever get this fixed cardana?

 

To properly adjust the idle you will have to warm the engine to full temp, unplug the sensors circled in the picture, you will have to unscrew the idle screw about 2 or 3 full turns since it's all the way in. Start the car with these sensors unplugged and adjust. For the first few seconds the idle will be high but should come down.

If that doesn't work than try adjusting that stop screw mentioned earlier.

 

hmmmmm....I'll have to try that. I always try to adjust the screw while the sensors are plugged in.

for the record no I have not fixed the problem yet...I am going to get an IACV and see if that fixes it. I'll report back when I swap the IACV.

 

Hey thats a picture of my engine before the VI... lol

 

I think you need more armor all on your throttle cables

 

I heard that if its ultra slick and shiny thats 30whp? Did those ricers are the rice convention the other month lie to me?!

lol

 

have u check the maf ? when my idle was acting up i had to change mine

 

no I have not checked my maf....I assume if that was bad I would have more problems other than at idle. The car runs smooth at all rmp's it, just idles high and surges up to 2K when I clutch the car when coming to a stop. I just ran the car at the track and it ran a 14.2 so I think it running fine over all.

When your maf went bad did it only act up on idle or did your car have other issues when running?

 

sounds like it could be a leak, did you put on a new gasket or re-use the old one?

 

Sorry! I needed an example and that was the cleanest picture I could find.

Cardana25, I would strongly suggest adjusting the idle with those 2 sensors unplugged, that's what every book says to do. Your IACV is probobly fine. Sure you can fine tune the idle with those sensors plugged in but not very much. You gotta unplug those bastards!

 

ok, so you are saying warm the car up and turn it off. Then unplug the sensors. After they are unplugged start the car again. While the car is running unscrew the plastic screw on the IACV 3 full turns. Then do I plug the sensors back in while the car is running? Or do I turn the car off and then plug them back in? Should the idle correct its self when the sensors are plugged back in?

As for my TB gasket I did not use a new one, but I figured if this was the problem, it would be taking in extra air past the maf and cause the car to run crappy.


**also for the sensors that you have circled is it just the brown and grey one? Or do you un plug all of them that are hooked to the IACV (I think there is a purple one too)

 

let us know how it turns out after you do the procedure crazy97 said. The high idle can possible be fixed, but the surging may be a leak. did you tighten everything to spec? Have you thought about putting a grounding kit or cleaning the grounds.

 

I have not done anything with the grounds since I did an engine swap. I did not think of checking those.

 

Warm the car up, maybe drive it for a few minutes to make sure.
Turn it off.
Unplug those two sensors.
unscrew the idle screw about 2 turns since it's all the way in.
Start car. Wait couple seconds.
Adjust idle, if it's high screw the bolt in.
If idle is low, unscrew the bolt until the idle comes up enough.
Shut off car.
Plug the sensors back in.
Start car and fine tune the idle if nessesarry.
Hopefully this will work.

 

cool man, I'll try it when I get back to my house from work.

 

Ok, I tried this but I am not sure I unplugged the right two sensors. Can you please tell me the colors of them. When I did this and started the car back up the idle went to 1500 then reved up to 2000 then back down again, just a constant up and down from those two spots. Did I do something wrong? What I did, did not help out at all. Thanks for the advice though.

 

One is brown and the other is grey. They are side by side. I've never had the idle go up and down like that over and over.

 

might as well check your TPS, since you have checked just about everything else. I had a similar problem last year and it was challenging to figure out. But it was the TPS that had went bad. Everyone on the org said it was either my MAF, IACV, or coils. All of those were fine

 

Have you looked at your throttle cables to see if they might be too tight? And have you ever messed with that stop screw on the TB?

 

Just to eliminate some things, I completely disassembled the IACV and cleaned it out real good, but I still get the surging. I also cleaned/recharged my K&N air filter and changed all the spark plugs with new NGK's.

This idle issue only started happening after I took the supercharger off temporarily for a rebuild. Problem is it doesn't always happen. It only happens sometimes, whenever I've been driving the car for a while, it will just start idling at 1500rpm for no good reason.

 

throttle cables are fine....if they were stuck up a little bit then it would not surge, it would just stay high.

 

let me know if you figure anything out too....I sould have a different IACV on the car by this weekend. I tried setting the idle again by disconnecting the grey and brown plugs and I still get the surging.

 

ok I put on a diffrent IACV and I am still having the exact same problems. I am still idling at 1100. I am thinking that the problem is the TPS. I have to **** it all the way towards the passenger side to get the lowest idle possible, but when I do this there is play in the pedel before it engages the pedel so that is super annoying. I was under the impression that is the TPS was set correctly it sould be pretty close to right in the middle (not cocked one way or the other). I could not find my multi meter last night so I could not test it.

 

the only way to make sure the TPS is correct is with the multi meter and feeler gauges

 

Any update on this cardana? My problem is getting worse and worse. Plus I just stripped the plastic IACV screw just now when I was trying to force it to be more closed. Some of the old threads point to a faulty TPS, so that would be my next guess. Did it end up being the TPS for you? I'm going to try to the TPS rotation fix.

Also, when I unplug the brown TPS connector and start the car, it idles superrr high at almost 2000. That might have something to do with it....

 

hahahha....yeah I have to turn my IACV screw with pliars. My IACV screw is all the way down and I am still having the same problems. I did order another TPS and it should be here this week. I'll update you once I replace that. I tried adjusting my TPS sensor with out a multi meter, I just cocked it all the way towards the manifold...that's where it gave me the lowest idle speed, but the throttle response is off now. I'll let you know if the tps does it.

 

I successfully adjusted the idle on the 95 last week. I would first back out the IACV valve a couple of full turns. Have the car warmed and then turn off. Turn the ECU screw all the way to the right, unplug the two sensors like previously mentioned, I think they are the TPS sensors. Put car in N and start. Adjust the screw on the TB to desired RPM then turn off car. Turn ECU screw back to the left, attach the two sensors and start. I got this info from this site and it worked for me!

 

did you have a surging idle or just a high idle? I have tried this several times but I cannot get my car to idle under 1k.

I just got a new TPS in the mail yesterday, so hopefully I can get that put on the car this weekend, and I will report back.

 

So that's all well and good, but what if your ecu screw is stripped? That is the problem I have, once while doing a self diagnostic, the screw basically turned to a white powder on me. Not sure where on the idle it broke at either... But I do know that my surging idle is very bad and affects driveability almost constantly now.

 

tried switching MAF sensors, both worked fine. TPS, both worked fine. PCV valve, both worked fine. cleaned IACV, have one coming from an org member soon. cleaned TB, and all electrical connections. Switched back to complete stock air intake, didn't help. Switched back to my K&N WAI after recharge, nothing. checked plugs for gap, torque and visual inspection seemed fine.