In the past few days the temp has dropped from around 0C to between -10 and -15 overnight, and its expected to get colder. Ive noticed that when I start the truck up its revving much higher than it usually does and its also not very steady.

It usually (cold engine in warm temps) will sit spot on 1400 rpms until it warms a bit and then it idles at about 800 rpms when warm.

Now its shooting straight up to 1800 - 2200 and kinda goes up and down between those values for a good 5 mins or so until the temp gauge starts to move off cold.

What would be some things to check or suggest that my mechanic checks? This never happened last winter, though last winter I was parking in a heater garage half the time and the winter was much milder.

Thanks!

 

sounds like its revving too high when cold it will surge like that when it revs too high, not sure how to reduce the cold idle, Not sure if the a/c idle up is what brings the idle up or not, but if you lower the cold idle abit it will stop surging!!

 

I think the IACV ( Idle Air Control Valve) has lots of the RPM control when cold.

Allows extra air to into the intake, bypassing the throttle body, till the coolant reaches _____? temp then the valve shuts and airflow is back to just the settings on the throttle body BBS (big brass screw).

I'm sure there are other things???? and I'm not even sure the proper check for the IACV, though I believe it is in the FSM and has something to do w/ clamping the lines when ??cold/ hot ?? to see if it changes idle.

Best of luck

Repo

 

It's the IACV as mentioned above. Mine does the same thing.

 

There are a number of threads about this, as a lot of people have this problem. Aside from the "obvious" (like a bad plug wire, plug, distributor cap, etc) common causes of this are bad cold start injector, bad cold temp sensor, and TPS being out of adjustment. Although I think these all tend to act up in the low idle end (<1000 rpm). I been' workin' through this one meself!

 

Thanks for the replies. Does this mean my IACV might be on its way out? It didnt happen 2 years ago when I first got the truck and we had a similarly cold winter. Ill look at the IACV and see what I can find out.

 

most likely taking it out and cleaning it out real good works. My BMW has something similar to this as well. They have a problem with them too.

 

Have you ever tried cleaning it to see if it would fix the issue?

 

have you done any other modifications or work to the truck lately that could possibly have triggered this condition?

Whereabouts in BC are you? It's -17c this morning and freaking cold!

 

No mods or anything recently or ever as far as I know. Im in the Okanagan and its about the same temp. -16 or something now, got to -22 the night before last

 

I've cleaned it but had no change. I need to replace it but it is a pain in the butt to remove from the throttle body.