Engine idles down in cold weather.

[Mr. Remarkable]

I've got a 2001 Sierra with a 4.8 liter, that idles up and down (almost turns off) only on start up with the engine cold. Once the engine warms up, the idle levels out to normal. If I leave it sitting for a while and let the engine cool back down, which in this winter weather it takes just a couple of hours, it'll do it again. It started doing this when the temp dropped outside around 30 degrees. Anything above 30 degrees outside temp, it doesn't idle up and down on start up. Even if the engine is cold.

Any input would help, Thanks

_Mike

 

[Molson02536]

I've got a 2001 Sierra with a 4.8 liter, that idles up and down (almost turns off) only on start up with the engine cold. Once the engine warms up, the idle levels out to normal. If I leave it sitting for a while and let the engine cool back down, which in this winter weather it takes just a couple of hours, it'll do it again. It started doing this when the temp dropped outside around 30 degrees. Anything above 30 degrees outside temp, it doesn't idle up and down on start up. Even if the engine is cold.

Any input would help, Thanks

_Mike

Start with the simple and clean your throttle body, make sure you use throttle body cleaner and not Carburetor cleaner. Carb cleaner is to corrosive to the gaskets used on throttle body's and make sure you pay attention to the IAC (Idle Air Control) valve passage ways.

Common for Carbon to build up and cause the IAC to stick in cold weather and in the summer time when there is lots of carbon deposits.

Good luck and keep us posted.

 

[Mr. Remarkable]

I cleaned the IAC (carbon build up was sticky) and the idle has changed a bit, it's better. I'm betting that that's the problem. I won't know for sure until Wednesday when the temp drops again, we're back up to 45-50 degrees, Texas weather is crazy. I'll keep you posted.

 

[Dirtman09]

Anything new? I posted a thread about my 2010 Sierra doing pretty much what yours was doing...