Anyway, I have a '74 2.0 liter with stock Djet injection. I had a problem with a frequent stumble, like a miss, that would happen when cruising down highway, especially at any steady speed. I went throught the necessary steps of checking timing, adjusting valves, checking ohms at every relevant connector I could think of, etc. No luck. Replaced throttle position sensor circuit board. No luck. Eventually, borrowed a few important parts to swap out one at a time. No change.
I hooked up a wideband O2 sensor, and got one decent clue: the A/F ratio was going "rich" briefly when I felt the stumble. Through checking online, an ignition miss should show up as "lean", so I tentatively ruled out ignition fault.A call to Brad Mayeur provided the right place to look. He mentioned that sometimes the "ball contact" at the end of the metallic finger that rides on the curved throttle position switch circuit board track can sometimes wear "flat" so it contacts a larger spot than desired. I took off the TPS to check this, and found that my problem was similar, but different. In my case, the metallic "finger" was twisted just enough to allow contact along its edge, in addition to the ball contact point. A gentle twist to straighten it, and a quick test drive verified the fix!
Smooth as butter since!Strange thing is, I tried unplugging the TPS a few times earlier in my diagnosis, and still had issues. However, I can only assume that maybe there were other problems that got fixed or improved along the way that may have been causing poor steady RPM running even with the TPS disconnected.
Anyway, tons of thanks to Brad for his help in solving this mystery!
Ken
Good for you!
