RPMs surge when at steady speed

[Capot]

Explanation - between 30 and 65mph while keeping the speed and rpms as steady as possible I can see on the TAC that the rpms rise by about 100 or so and I can actually hear it through my flowmaster exhaust. For instance at 40mph and 1400rpm I can see the TAC go up to 1500 then back down again this continues about every few seconds. I had a thread on this earlier but the opinion was that it was just the exhaust. At idle the rpms are steady. Above 70 I don't see this, it starts around back when speed drops to around 65. Neither the SES or check engine light are on. Anything simple I can check?

[ACiFiC]

Re: RPMs surge when at steady speed

Try Transmission fluid

[Capot]

Re: RPMs surge when at steady speed

Checks good, right at the top of the crosshatch. That was about an hour after I got home from work, I'll check it again tomorrow when I get to work.

[bigbrian442]

Re: RPMs surge when at steady speed

Torque converter clutch may be slipping. The faster you drive the higher pressure the trans pump makes, so it slips less.

[Capot]

Re: RPMs surge when at steady speed

Hmm, didn't want to hear that. Every time I get my tax refund in something comes up. Guess I need to get it check out.

Thanks

[Capot]

Re: RPMs surge when at steady speed (Solved)

Pretty embarassing actually, my son who also drives a 99 Firebird suggested I change the air filter - that did the trick.

Thanks to all who replied.