Just bought a 2002 GMC Sierra pickup 4x4. Been having problems with this truck since buying it....

Most recent problem is when starting it first thing in the morning when it's cold. i'm talking -15 -20C (Ontario Canada).
Truck starts fine but after 5 - 10 seconds the idle slows down and begins to chug, then stall. I can restart it but it will repeat.
If i play with the throttle and keep the idle up it will stay running.
After 3 or 4 minutes the truck will warm up a little and idle on it's own.
Once the motor is warm it runs great!

No check engine light, truck has 240,000kms.

What could be the problem?

 

Check your throttle body to see if it is dirty inside. If so, buy some throttle body cleaner and clean the crap out of it. They get so carboned up that they will act just like your saying. If thats not the culprit you might need a temperature sensor.

 

Thank you for the info, i will check that out tomorrow.

Will also include the fuel gauge problem that i'm having, the gauge bounces back and forth from empty to full and all spots in between.. After searching the forums i can see this is a common problems on the 2000 - 2002 trucks.

Only hope it's just a dirty throttle body and not a fuel pump....

 

Checked the throttle body and it was very dirty, black inside.
Used a clean rag and some throttle body cleaner and sprayed/wiped it all out inside. Lots of yucky stuff came out. Once it's a bit warmer outside i'll redo and throw a toothbrush inside.

Engine didn't start the best right away but cleared up and idled nicely.
Will find out tomorrow morning when i do a cold start.

here's 2 pic's before i cleaned it up.

 

If your TB looks like that, then your IAC valve will probably be worse. Taking off the TB and cleaning it would be better. The IAC valve is what chokes it for cold start ups. Try cleaning this thoroughly to see if this helps.

 

Is it very difficult to remove the throttle body off this truck?
I've worked on other engines before but this is alot newer then my old 92 sierra.

 

Not to hard - it has 3 bolts, the wiring plugs, throttle cables, and a coolant line under it. The coolant line is the biggest pain in the ***, but it will come off.
I hope that clears it up. It is normal for it to run funny for a few seconds after cleaning the throttle body. The motor will get all that crap in it. That is another reason it is better to remove it, but you won't hurt anything. Good luck!

 

imo, best stuff in the world for cleaning carbs, throttle bodies, fuel injectors etc is Seafoam. Stuff does an unbelievably great job. I buy it at Advance Auto Parts or O'Reilley's.
On something that I know is dirty, I use more then the bottle says. I have used up to a full bottle in a half a tank of gas on a motorcycle.
Stuff really is fantastic. Saved me from pulling more then one carb due to varnish, dirt etc

 

Has anybody messed with the throttle adjustment screw???? The butterfly valve looks like its closed all the way.....sounds like a TPS or IAC to me especialy if it only does it cold

 

Dont think these TB's have an adjustment screw. The flap does close all the way, so the computer uses the IAC pindle valve to adjust for incoming air for loads or cold start ups. But I agree, the IAC valve has to be gettin stuck or its bad.