Rpms are going crazy?!?!?

[dogcmp6]

The past few months my RPMS have been going crazy, spiking between 200 and 1000 (and you can hear the revving when this happens to) when I am coasting, braking, or driving at a low speed, since I have a hard time explaining things, here is a video of it 2003 taurus rpm issue - YouTube any ideas what could be causing this?

[behlinla]

Are the engine RPMs actually changing with the tachometer? I can't really hear the engine in your video (microphone covered?).

If the engine sounds like it's running steady then I would suspect a crankshaft sensor.

[dogcmp6]

Originally Posted by behlinla

Are the engine RPMs actually changing with the tachometer? I can't really hear the engine in your video (microphone covered?).

If the engine sounds like it's running steady then I would suspect a crankshaft sensor.

Oops, I meant to add that I can hear the engine reving with the tach

[behlinla]

Okay, then it's probably an IAC problem. Take it off (two bolts, save the gasket) and see if it looks real dirty.

[dogcmp6]

Pulled off my old IAC, there was no gasket, and the inside was dirty as all hell, bought a new one, popped it on with the gasket in 5 minutes, drove around for an hour, and no more problems!!!!! im so happy

[behlinla]

Congrats, glad it's fixed.

[dogcmp6]

Well, my rpms are no longer erratic while I am coasting, but now when I am at a stop, the rpms keep moving between 6 and 900

[behlinla]

You should check for vacuum leaks.

[dogcmp6]

There was not a gasket when I removed the old IAC, and I installed the new one with a diamond shaped gasket that was in the box, would this have anything to do with it?

[behlinla]

If you used the ∞ shaped gasket and your throttle body don't have a groove for it to fit in it's going to leak. If you have a flat surface, then you need a flat gasket like this: