The last two weeks I've been noticing something odd.

When I start up the car and drive off, it starts and goes normally. Then I roll up to a light and stop. The rpms drop all the way down to 500 then up to 1000 then down again, and it finally settles in at 750 like normal. This happens a couple times then stops once I've been driving for a while.

It's a worse if I have the air conditioning on. It'll happen the same way but won't stop.

The only change to my car recently has been a new battery about a month ago.

 

It could be the A/C kicking on and off, it could be the PCM making adjustments due to a poor signal from the battery or alternator. Everything is controlled by the PCM, something is obviously bothering it. Injectors could also be a little clogged causing variations in fuel mixture. When was the last time you changed your fuel filter?

 

Or the last time you ran a tank of gas with a fuel system cleaner?

If you have your heating system on DEFROST, it also runs the compressor so that would act like the A/C was on.

 

Clean the MAF sensor and throttle body

 

The fuel filter was changed 2 months ago - its been about 3k miles. I haven't used a fuel system cleaner.

Thanks for the quick responses guys. I'll give this stuff a shot.

If anybody got more idears keep em comin.