Engine Mechanical problem
1996 Geo Prizm 4 cyl Front Wheel Drive Automatic 83000 miles
When I start my 96 Geo Prizm car when its cold, there is alot of what seems to be engine vibration, felt inside the car during high engine idle. The idle drops in speed to around 1000 RPM, once the car is fully warmed up in about 15 minutes. And then eventually drop to around 700 RPM after another 5 or 10 minutes. At 700 RPM, the engine quiets, and the loud engine vibration is gone.
Same thing when driving, if I do not let the car warm up for 15 to 20 minutes, I feel alot of vibration in the cab when I drive, until the Idle drops to 700 RPM and then it drives perfectly fine. I had the motor mounts checked, I was told they are worn - but seem to be ok.
My main concern is Engine Vibration - it is strong enough to make the hood and front fenders vibrate to the noise of the engine when warming up, then its fine!
Sensor check showed all sensors working!
I changed wires, spark plugs, and rotor cap/button.
I'm at my whits end to trying to resolve this - having several day - here and there - trying to figure it out!
Trying to avoid going to a costly repair shop - any solid advice would certainly be most helpful!
I have the same problem and have been researching it for a few days now and so far it is sounding like one of the three mounts(motor or transmission). My vibration is more prominent toward the #1 cylinder (pass side). Its either the motor mount or the harmonic balancer is rusted because it has a bit of woble to it. I will post my resolution here once I know for sure what it is.