Hello. I own a manual 1993 Ford Probe, and it has given me a strange problem I simply ignored for a little while. But now I am traveling more often and I started to worry about it.

After driving for a while, such as on the interstate for more than half an hour, the engine revs down when I have the clutch down and take my foot off the gas, such as stopping at a red light in town. The engine revs downward from 1.5 RPM, it's normal neutral position on the tachometer, down to 1 and back. It revs down in a pattern, every 10 or 20 seconds at a steady rate.

I have found it tends to do this more often during the summer, but will still do it during the winter.

I mainly am worried about what it may be doing to my milage, my engine, and people who look at me strangely, as it sounds like I am revving up my engine for a race with them.

I think your throttle position sensor is going bad. If you have a tester monitor the voltage. You can check the ohms. The resistance should as the accelerator pedal is pushed. Look for abnormal jumps.