jimkf

My '99 Suburban is exhibiting an issue where the engine doesn't return to an idle until I've come to just about a complete stop. If I get the vehicle up to about 45 mph (12-1500 rpm) and take my foot off the accelerator pedal, it's as if the cruise control is on. I've also noticed that it's using a little bit of coolant as the overflow is empty. Could this be a vacuum leak between the upper and lower intakes? I've heard that the gasket between them tends to go bad. Any thoughts?

jimkf

I think I fixed the issue. The coolant loss was compliments of worn intake gaskets...in fact they were totally rotted away at the front inlets on each side. I replaced them and after about 50 miles of driving, my high idle issue disappeared. My guess is that the vacuum created by the leaking gaskets was causing issues with the ECM. All seems well now!

Jusjoe

Thanks jimkf. Symptoms totally match my newly acquired 99 suburban. I guess I have more work to do before I put it to good use.
Be blessed my friend.

Jusjoe

I found that I'm not loosing coolant as mentioned by jimkf. When I get the symptom that feels like the cruise control is on after releasing the gas pedal, I can drop the idle by putting the trans in neutral. Where would a vacuum leak occur only when my vehicle is in gear? Appreciate any input.