GMC Idle Problem

hybridtj · October 28, 2003

I have a 2001 GMC pickup with the 6L engine. Truck has about 45000 miles.

I have a problem where the truck stalls quite often, always under the same circumstances. When I am pulling into say a parking spot and am slowing down or braking, the rpms drop pretty low. Then when steering into the parking spot it is like the power steering pump adds just enough extra work to the low idling engine that my engine stalls. Once I restart the engine, the idle speed is always sufficient to run everything.

This never happens when just coming to a stop only. It is only when turning while coming to a stop. Its like the idle drops too far before it compensates back up.

Any suggestions about what to do or what the prob is? Air filter is clean, fuel filter is new, all that kind of stuff.

Any help would be appreciated.

asepgrad98 · October 29, 2003

first thing i would do is clean the throttle body and have the PCM updated at your dealer

hybridtj · October 29, 2003

Thanks for the reply. What is involved in having the PCM updated by the dealer?

One other thing that I was checking yesterday. If I am sitting at idle and I turn on the defroster for instance, the idle drops pretty low and then recovers. I can make it do that repeatedly if I keep turning it off and on. Why does the rpm drop so low like that? Is the idle just set too low?

Thanks

asepgrad98 · October 29, 2003

the idle drops because the defrost puts a huge load on the alternator. if your still under warranty then you may be able to get the dealer to update the PCM for free. otherwise 70$ or so.

hybridtj · October 30, 2003

Thanks. I guess I'll clean the throttle body and call the dealer. Do I just make an appointment and tell them that all I want done is to have the PCM updated? What does the anacronym PCM stand for exactly, so I don't sound stupid? Thanks again.

silverado man · October 30, 2003

PCM is the Power and Control Module. Basically the trucks computer.

hybridtj · October 30, 2003

Thanks.

GMike · December 11, 2003

Your problem sounds exactly like mine! Here is my post:

Any ideas what to check for this? I have a 2002 Escalade with around 60K miles. I have recently had the fuel filter replace, new Bosch Platinum +4 plugs, changed oil to Mobil 1 (w/Fram doubleguard filter). The truck runs strong, but after it gets warmed up and I come to a stop, the idle starts to drop below 500 RPM's. The PCM seems to catch it some of the time, and tries to keep the engine running, but occasionally it dies. I put it back in park and she starts right back up. Unfortunately, it just seems she wants to idle at too low an RPM.

I have a preditor programmer and can change a few things, but not idle (not for 2002). Any suggestions as to what to monitor, and or change? I also noticed the knock sensor retarded timing at WOT. So, I richened up the fuel mixture a little bit. So, far no difference regarding the "idle stall" problem when using the stock program or the preditor programmers standard performance tune.

Your help and suggestions are appreciated.

What did you find out? Did you find a fix? Throttle body cleaning work? I would love to know!

Regards,

Mike

TexMan · December 12, 2003

Also have them check the ECM.

chuckp · December 12, 2003

First i thing i would put ac plugs in it.Also if you put your serial number on this web page it will tell you if there is a update for your computer.

http://calid.gm.com/vci/

chuck

GMike · December 12, 2003

Hey, thanks! That was a good link. I ran my VIN and the Engine Calibration mentions a "New calibration to address idle surge condition caused by throttle body coking, to be used in conjuction with throttle body cleaning."

So, I will use my programmer to se if the CVN# 0000E4E8 shows up in the PCM. If not, I guess I will need to show around at a GMC dealer (Cadillac is too expensive). I would think a chevy/GMC truck shop should be able to do both procedures, recalibrate and clean.

Any other suggestions?