I have removed my Tach filter and taped off the wires. The tach usualy is at 0 rpm. but if I lay into it the tach will jump all over it never seems to drop below 0rpm or above 3k rpm. what could cause this?

Guess that tach filter was there for a reason. Get a Rodney Dickman replacement.

could be picking up noise. could be a wire rubbed thru someplace and the vibration makeing a false signal.

Could that be at reason the car surges at constat rpm? it'll surge hard enough to chirp the wheels in 2nd. but it will idle fine, it seels to miss a bit at WOT but the real problem in the surgeing during normal driveing. I'm hopeign to have it back on the road in "Good shape" by next weekend.

The Haynes manual is telling me...

Engine surges while holding accelerator steady. (I'm assuming this means RPMs are not holding steady at a steady speed)

- intake air leak
- fuel pump faulty
- loose fuel injector harness connections
- defective ECM

If your RPMs are steady and the tires are chirping then I'd say it could possibly be something in the tranny. Prob the clutch... that's if your's is a stick. I don't know, could be the lockup sensor too. Maybe someone knows for sure what could cause that.

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HugGRRRFiero@hotmail.com

My 86 Gt was doing exactly the same thing a couple of weeks ago. The tach went crazy while holding the throttle steady at cruising speed and would miss at that stage something awful. I started by changing the plug wires. CURED THE PROBLEM...Hope that works for you. I really thought is was going to be something more serious, because the wires were really not that old. Conrad

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Radcon