Hello. Got a 95 with the 3.1. When I bought the car a couple years ago I did a complete maintenance on it including running computer codes only to find out that I can't link to the computer. No biggie, no problems anyway. Fast forward- A couple of months ago I jump started my Girlfriends-sons car with my monte and ever since it has idled way too fast. Around 2600rpm on startup and after a few seconds slows to about 1400rpm until I put it in gear then back up again. Since I can't link to the comp I really don't know where to start with repair. Did I fry a sensor? ECM/Chip?ARGGG!!! Any ideas or suggestions would be very helpful and GREATLY APPRICIATED!!!!!!
Thanks, Nomad59

 

Wow, nobody has touched this thread. I would recommend bringing it into a garage at this point. Your going to be running OBD 1.5 I beleive and I am not familiar with a scanner that will pull that.

 

you could have a vacuum leak. check the plastic hose connected to the pvc valve. It makes a "T" connection to the intake manifold on top. it's probably lifting up or not seating right. on my 96 beretta, I was able to wedge in cardboard on top of the hose to hold it down at that spot. high idle is often a vacuum leak somewhere. if it's not where i said, check all vacuum lines. as long as you didn't hook up the wires wrong when jump starting, I don't think you fried anything. could just be a coincidence. You could unplug the battery over night to reset the computer to let it relearn everything.

 

try adjusting it..there should be an adjustment screw on the throttle body iself...have sum1 in the car and put it in drive and hold the brakes...u turn the screw un it get to about 100 or a lil less...usually 1k is a good idle....and there no mods to the engine right...like cams or anything...

 

there should be no need for adjustment!! It's not like the old days of carburators. the idle air control valve controls the idle from the computer. there should be no adjustments needed! something else is wrong. maybe a vacuum leak or maybe upper intake gaskets are creating a vacuum leak. but DON'T adjust anything. That's not the fix.

 

agree'd the only time to mess with the throtle set screw is if you dissasembled the TB and Ported it. like i have.... but NO do not play with the screw on the TB.

High idle is normally caused by a intake leak. so chances are something is letting air in. if thats not the prob, it could be a sensor. take it to a dealer or shop that can scan it and diganose the prob. i hate to tell you that but atleast you will know what your dealing with.

 

Maybe this will help. Your engine breathes just like you do---through your mouth an nose. The engine's mouth is the throttle plate which is totally closed at idle. Do NOT try to adjust it in any way. It's nose is the idle air control valve which is an electrical motor. This motor (driven by the computer) controls the air intake at idle when the throttle plate is closed. It has it's own air passage which by-passes the throttle plate. If you do not have a intake manifold, vacuum hose, or any other external leak to the engine --- then it has to be the idle air control system. They get dirty and full of gum and varnish which are by-products of gasoline. Find the valve located somewhere on the throttle body and remove it if you can. Get some throttle body cleaner (NOT carb cleaner) and spray the valve assembly and the throttle body chamber it goes in. Use the entire can and let it set for about 10 minutes. Re-install the idle air control valve onto the throttle body and see if that cures the problem.

 

OK, first off, did you jump it STRAIGHT off the battery? That is a HUGE no no. That can fry the ECM and Prom. Secondly, the OBD 1 was used until 96 so my guess is its an OBD1. Snap-On sells a scanner for it, but thats WAY too expensive. If its a typical Chevy, run a paperclip to (If I remember correctly) A&B connections on your ALDL, they should be the ones on the far left VERTICALLY. Lastly, what it sounds like you have is a fried IAC valve, hence its stuck shut, can happen when you jump a car and surge the system. The IAC is a three wire connection on top of the Throttlebody, generally sitting at a 90 degree angle to the TB. There are 2 Torx screws(t-27, I think) that hold it in. Swap that part out, should run about 15 bucks @ Advanced. and if you restart the car and the idle is STILL high, it CAN take up to 15 minutes to reset a new IAC valve. BTW Advanced Auto Parts offers diagnostic tool RENTAL, and (usually if you use it in their parking lot) its can be free. Easiest way to tell if youre OBD 1 or 2 is OBD 1 is rectangular and solid w/ plug reliefs, OBD2 is VERY distinguishable too. I am an auto servie technician I see that all the time.

 

Hmm. Considering it's been a month, has only posted once,and he hasn't replied I don't think he's going to be checking this thread anymore. =<