Cold Idle Issues

yfz450_117 · January 27, 2007

Hey guys,

I also posted this in the gm technician section. I'm a newbie here and I'm just looking to get some replies. By the way, great site! I have a 2002 Silverado 1500HD. I'm having some cold idle issues. It starts fine. Idles up to around 1200rpms, then it dips way down to around 500 (normal idle) and spits and sputteres then it will surge back up to around 1000rpms. It does this for the first 2 minutes or so of running. It is like it is too cold for it to idle that low. Once the truck has been running for a good 3-4 minutes, it gets better and better until it is warmed up then it is completely fine for the rest of the day. It only happens when I let it sit overnight for like 10 hours. The colder the weather the worse it is. It actually shuts off on me. This morning it shut off twice on me. I've replaced the coolant temp sensor and that didn't help. I've cleaned the throttle body and IAC valve and that seemed to help it run a little better. It seemed like it had a bit more power, but it didn't help with my cold idle issue. My mechanic is pretty confident that it is still the IAC valve. Even though I cleaned it, it still may not be working properly. I was going to check for an intake leak today using the starting fluid method and see what I come up with. My mechanic is steering me away from the intake leak. He says it would do it all the time if it was the intake, not just when cold. I guess my question is, is it sometime necessary to replace the IAC valve?? Does cleaning it not always cure the problem?? The IAC valve is $120 bucks at advanced auto that is why im hesitant on getting it. Could it be the throttle position sensor? I can get that sensor for $30 bucks. Thanks in advance for your help.

diehrd · January 27, 2007

Are there any codes ? ? ? A check engine light ? ? There should be something logged and most sensors when there giving up will generate a code

yfz450_117 · January 27, 2007

Nope, sorry I forgot to mention that. I'm not getting any check engine lights. I didn't get it checked for codes though.

kdog55 · January 28, 2007

Hey Kale, after talking to you at work yesterday, I checked with my neighbor Shawn S., and told him your problems. As expected he said it is hard to say without looking at it, but one easy thing to try is some dry gas, as he has had a rash of water in fuel poroblems around here. If not then he said he would check the throttle positioning sensor or maybe the MAF sensor.

I'll talk to you at work, man.

~~~~~Koondog~~~~~

GeoHawk · January 28, 2007

I had the exact symptoms you did and ended up being a leak in the intake gasket on my truck. The dealer replaced it and it runs fine now.

yfz450_117 · January 28, 2007

Thanks for the replies. I think it is the intake gasket leaking. I sprayed carb cleaner around the base of the intake and at one spot the engine stumbled every time I sprayed it there. I guess I'm going to get the gasket changed and hopefully that clears my problem up.

Thanks for your help koondog. I had already tried the dry gas and it didnt seem to help. I tried a number of different sensors including the throttle position sensor and they didn't help either. I'm almost positive it is the intake. I'm gonna have Dave put a new gasket on for me.