GMC Envoy XL 2003 Idle Up and Down

[timezone]

:( My Envoy has been giving me problems since I replaced the temperature sensor(sender), thermastat, and the fan clutch. Now I'm getting a problem when I turn my heat on. The car idles up to about 1and a half rpms then it drops all the way down to zero rpms and then it shuts off. (only when in park). If the heat is turned off it runs perfectly fine. Does anyone know what tcould be the problem ?

[protech]

The problem you are having is due to excessive carbon build up inside the throttle body. There is more load put on the engine, especially at idle when you have heater or air conditioning running. When the engine can't enough air, due to the carbon build up, the idle dips very low and often times ends up stalling out. What you need to do is remove the air filter ducting and plastic housing that attaches to the throttle body. With an approved cleaner, like brake clean or comparable cleaner, you should spray all inside the throttle body and throttle blade, then spray a rag and wipe out the inside of the throttle body housing really good. There will be a black residue from the carbon that you need to get all cleaned out of there and on the throttle blade as well. That will take care of your problem.

[Luvlylane]

What causes the emc to have to be replaced in 2004 gmc envoy

[ProTech]

Usually an internal failure will require the PCM to be replaced in any vehicle. Depending on what trouble codes you had stored, they can lead to PCM replacement as well.

Or, if the technician was unable to communicate with the PCM, that can be cause for replacement as well.

There are lots of reasons that can determine if the PCM needs replaced or not, so I can't really give you a specific answer.

[csherman]

Our '06 Envoy head lights have a mind of their own much of the time they stay on for an excessive amount of time killing the battery. Some times they go off immediately, I've even seen them come on while parked. There is no adjustment for how long they stay on so what controls them?

[carriedi]

the headlights are controlled by the body control module under the left rear seat on rear fuse block. Try scanning the BCM and see if there are any codes. Is it just the headlights that come on or does the running lights come on too. the lowbeam relay is #46, the highbeam is #43 (under hood fuse block) and the running lights relay is #30 (in rear fuse under rear seat)

[LuvGMC]

I have a GMC Sierra..checked all the relays and grounds. The truck will not shut off until the one of the head light fuse is taken out. When headlights is switched to off the fuel pump shuts off too. Why would the headlights have control of the relays?

[carriedi]

GMC Sierra wiring diagrams change over the years. What is the year, model, engine, trans and drive train (2 or 4wd) do you have?

Also you say when you one headlight fuse, which one? or does that make any difference? Either one can shut off the fuel pump?

Here's the thing, it's gotta be more than just the fuel pump that keeps running. Or are you saying the fuel pump keeps running but the truck shuts off? If the engine keeps running then it's a lot more than the fuel pump keeps running. That would mean the the computer is not seeing the ignition switch power off. That why the spark and fuel injector keep working as well as the fuel pump. If the computer doesn't see the key turn off I would look for a short to power somewhere in the computers battery feed wire and the power to the headlight power circuit.