Engine Performance problem
1991 Ford Probe 6 cyl Front Wheel Drive Automatic 188000 miles
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My car was running great until I got near my home where it started to run rough and surge. The condition continued for several weeks continuously while at my mechanic. He tested the fuel pressure, compression, dropped the exhaust. Found nothing. Apparently there is no way to check for trouble codes. I tried the dealer; I don't think they looked at it. I changed the plugs, cap, rotor, fuel filter. Same. I let the car sit for a couple of weeks, it mysteriously started running fine again but only for a few miles. Seems temperature might be involved. I changed the ignition control module, but it's still running rough after a few miles. The tachometer is all over the place and stalls when in reverse while it's acting up. It's an old car, but is still in good shape. I have a feeling it's electrical, not mechanical. I am able to drive it when it's acting up, but it isn't pleasant. What do you think it could be?