Surging idle?

RACE.FAN3

MEMBER
2003 OLDSMOBILE AURORA
V8
FWD
AUTOMATIC
78,000 MILES

When the car is hot and at idle the engine surges - in or out of gear. The idle speed is not smooth and constant it raises by 50 rpm and then drops by 50 rpm. I liken it to the motion of rolling a water balloon. My commute to work is approx 35 miles and hghway. Lately when I get off the ramp and go to pull out after stopping the car will bog then take off. It runs fine at high speed. The check enging light will come on after this episode but will go back out in a day or two. The code indicated a mass air sensor - it appears to be OK. In stop and go traffic the car seems to hard shift and not drop to an idle rpm until after a stop. At high speed when suddenly lifting the gas you get a backlash feeling. Any ideas?

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

There are a couple things that will cause this, so we need to start with these two guides and see if we have a vacuum leak or one of the other common causes for this.

https://www.2carpros.com/articles/engine-surges

https://youtu.be/4ktw1X4W_-k

The next thing is we need to check what codes are there so that we can find out if there is an issue that will point us in the right direction.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Basically, the code is what is going to be telltale. If it is related to this issue, then we are going to have to track that down. Otherwise, I am pretty sure you will find a vacuum leak.

Please run through this info and let me know what questions you have.

Thanks