Accelerating when idling and in neutral

CIBARRAS

MEMBER
2003 CHEVROLET MALIBU
3.1L
2WD
AUTOMATIC
140,000 MILES

Car overheated resulting in blown hose. Radiator hose was replaced, along with other hoses as they seemed to be expanded and close to breaking as well. Coolant cap and radiator cap were replaced as they looked worn, engine oil was not replaced
Days prior to that, the ignition would stick until the drive selector was wiggled a little bit, plus when starting up the car it will accelerate to 2,000-2,500 rpm's in park an neutral but drops to 1,000 or less in reverse and drive. It still did this after getting the car back and driving a mile out, stopping the car for errands and going back home, motor started sounding louder and very slightly resisting when brake was applied. Acceleration was still happening after parking at home. Any ideas are appreciated.

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

This issue could be a couple things. First and foremost let's check for codes. If you cannot check codes yourself, then stop by a parts store and they can scan it free of charge. Assuming there are no codes the next thing we need to do is check for a head gasket leak.

https://www.2carpros.com/articles/head-gasket-blown-test

I am thinking that due to the overheat we have some base engine issues that are causes other issues. If the head gasket passes then we need to do a compression check.

https://www.2carpros.com/articles/how-to-test-engine-compression

Assuming all this checks out and there are no codes, then we need to look for air leaks in the intake system. This would explain the louder engine and erratic idling. For this we need to look for vacuum leaks.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Based on the info you provided, I am sure we will figure this out with this info. Even if nothing changes with these tests, that will be good info as well.

Thanks