Engine Continously Revs 500 RPM

When I start my 99 EX V6 the engine initally revs higer than normal (around 2000 RPM) for about 5 seconds then goes into a continous sequence of reving from about 1500 to 2000 RPM once every second. Up and down, over and over again.

The reving stops when I put the car in drive and the car accelerates normally, but the engine shudders any time I release the gas pedal, and the it holds a high idle when braking and when stopped in drive. I can feel the car fighting the brakes.

As soon as the car is put into park again, the 500 RPM revving every second starts again!

Neither the throttle or cruise control cables move so it seems to be a computer or sensor thing. I checked the PCV valve and air filter. I've had the EGR valve replaced twice now (last time was in Oct. about 12,000 miles ago).

ANY THOUGHTS?!

Well, for any one who may have this problem in the future it was the Idle Air Control (IAC) valve. $260 for the diagnosis and replacement. Looking at it now its probably something I could have done on my own but oh well... live and learn.

:banghead:

Well, for any one who may have this problem in the future it was the Idle Air Control (IAC) valve. $260 for the diagnosis and replacement. Looking at it now its probably something I could have done on my own but oh well... live and learn.

:banghead:

FADEtoBLACK, I'm a real newbie. Just registered today to see if I could find the problem I was having. Boy did I hit paydirt. This is the problem I'm seeing down to the last detail.

I'm fairly handy, but I don't do much work on cars. What's involved in replacing the IAC valve?

yup sounds like the IAC valve. Its on the under side of the throttle body. It is easier to get to if you just pull the throttle body off.