Anyone? Im really in need of some suggetions here. Ive seen alot of posts on this problem. No one has posted any solutions. No one has figured this out?

 

Check engine mounts. Also vaccum leaks. Also very rare make sure cruise control is off. Never heard of it but one time similar condition.

 

Yeah already have checed those things and replace vacuum lines. Did just pull the fuel filter. Picking up. A new one after work tomorrow. Parts stores closed now since Sunday. It was pretty plugged. Could barely blow through it. Don't know if that would affect the idleing high in gear or not. Had wife holdbrake and put in gear and I watched to see. Throttle moves and it doesn't.

 

Within the last year my brothers 1997 did what you are outlining, high idle from time to time almost like a sticking cable or bad return spring. Ended up being funk built up on the throttle blade. Pulled the throttle body cleand it well with carb cleaner and no more problem. My speculation was because it was a EGR motor the intake air was "dirty" and caused a quicker build up.

 

I cleaned the TB few weeks ago. Seems like that is what causedt he probem to start with. It was fine till i saw all the build up and cleaned it up.
Just put new FF on, which was WAY PAST due. Didnt make anydifference.
New vacuum lines, new iac, new ff, clean TB again. Problem is still there. Only high idles in gear, Its an auto as well. You can sometimes do 40 without touching the accelerator. When idle kicks up, throttle cable does not move.

 

I am having a similar problem in my 94 ss 4.3 cpi. First starts it will die and will only start if u hold down easily on the gas. Few mins later will idle on its own but will idle around 850 to 900. U turn it off and back on it will idle down to 650 and then go back up to 850 to 900. Changed(IAC,TPS,MAP,FF,fuel press reg,) and still have the problem. Hopfully we can figure this out! Ur not alone on this.

 

Just because the IAC is new dont mean its good. As i recall there is some wacky relearn process for the mid 90's s10. and i THINK there is a plunger setting that needs adjusted on new. I know there is on the old TBI setups.

 

There is not a setting for anew IAC on obdII. Ivetried 2 IACs with the same result. Doubt 2arebad out of box. I dont get a code anymore for IAC. Just idle jumps up soon asput in D or R.

 

Researching your problem a bit... Has the VSS (vehicle speed sensor) ever been replaced? Or the wiring around it ever been jacked with?

 

AND what kind of condition is your EGR valve?

 

EGR valve is fine. But I'm looking into the vss possibility. I just unhooked it and did a test drive. Only problem is its an auto and won't shift past 2nd. And anti lock came on. But I puut in gear with brake on and rpms didn't not jump to 1500 like usual. Plugged vss back in and rpms went to 1500 in D with brake on . So thinking maybe vss? Its never been messed with. I've had jimmy 4 years.

 

I have had some very crazy driveability problems with various s10's and GM in general and several were cured by a VSS replacment. Not trying to spend your money but if it were mine and it was speed related I would look at / replace VSS.

If you pull your VSS you may be able to see a pile of clutch material collected on the metal tip of the sensor. Clean it off and try it again if you dont want to replace it.

 

For the life of me i cant find a VSS testing procedure. I have seen one somewhere but cant find it.

 

I think i will probably go ahead and replace it. If that doesnt work, I guess its time to lube up and hit the shop. Been messing with this for like 3 weeks or so.
At first it gave me P0507 for idle higher than expected. After some tinkering and TB cleaning fro a second time, and IAC replaced the check engine code has not come back. That was over 2 weeks ago. But the problem still exists. I dont know if its changed the problem at all, cause its been my wifes dd for last 2 years. I only occassionally drive it or when she says Check engine light is on.

 

Anyway by having a build up on the VSS sensor tip that is somewhat magnetic it tends to send a "dirty" VSS signal to the ECM.

Another thought and question have you replaced or checked your TPS?

 

Anyway byt having a build up on the VSS sensor tip that is somewhat magnetic it tends to send a "dirty" VSS signal to the ECM.

Another thought and question have you replaced or checked your TPS?

I hadnt ran any test on the TPS, From all thesearching ivedone on here about this problem. Seems alot had replaced the tps and it did nothing. I just recently came across possibly being vss.
Makes me hope im in the right direction with vss. With it unplugged, the rpms didnot jump up in D or R. Plugged back in and the do. Ill try cleaning it first and see what happens.

 

Well a known good working vss didnt fix it either. After i thought about it. Ididnt thinkit would.
The rpms jump up to 1500+ as soon as shifted into R or D. Even with the brake on and not touching accelerator. Soon as in P or N rpms go back to normal.

Surely someone had asolution to this problem as many problems like this came up in searches.

 

Well ive given up. Jimmys going into shop this week.

 

What year Jimmy? 4x4? When you start it and it is in park what does it idle at? If it idles, with the engine is warm at between 600-800 rpm, disconnect the IAC and shift into drive. Do the rpms jump?

 

Its a 97 4x4. 4wd works perfectly. As soon as i disconnect IAC rpms will jump upto 15-2000. So not a chance to shift into drive to see if they jump they are already there. Like isaid,in park its 6-800 no up and down or anything. Perfect idle till it goes ingear. IAC was swapped with a known for sure good one as well.
RPMS do the same thing with tps unplugged and with a different tps.

 

The IAC is a simple circuit. The VCM controls it and that is it. I suspect that if you have a normal idle in park and it revs in drive, the VCM is controling it that way. I do have one more thing to have you do. I would like you to start the truck and then disconnect the MAP sensor. If the engine doesn't die, put it in drive and see what happens.

My money is on the VCM being bad. You could try the "tap test". Have someone in the truck with it in drive and holding the brake and then tap on the VCM and see if the idle goes down. This was a common test for older PCMs.

 

Well today i go out to run the check you suggested,andof course its running fine. This problem doesnt always happen. But does most of thetime. Ill take it on a drive after the wife gets home for thekids.

 

Ok. Took it for a drive just a few minutes ago. Went on about a 10 mile drive and could not get it too act up. About 3 blocks from home i made a quick 3 minute stop and after restarting the jimmy. It acted up. Got in drive way and popped the hood. Unplugged the map sensor and put it in drive. Problem still there.

 

Yep, if I was a betting man, my loot would be on the VCM is causing it.

 

I must be drawing a blank, but what is vcm?

 

PCM with ABS integrated. Black 'ribbed' PCM under the hood on many GM products.

 

I just had the same problem with idling high in gear but my problem was a bad connection on the cts. I lost the rubber seal on the plug and that made the plug go all the way in and get a good connection. Now my car runs fine. Just a suggestion, hope it helps.

 

Ok. I'm lost. What is cst

 

Coolant temp sensor? How will that affect anything?

 

When problem is occurring give TB and all vacuums a light spray of TB cleaner. I would suspect a leak somewhere. The idle will change if the TB cleaner finds the leak. Make note of the area and start digging.