When driving at a steady speed of 60 to 70 MPH, if I tried to accelerate slightly the engine would buck a bit. If I accelerated more aggressively it would kick down a gear and there would be no bucking. I originally thought it was a transmission problem, but came to believe it might be a bad throttle position sensor. I changed the TPS last this past weekend, and the bucking problem was eliminated. Not only that, throttle response is hugely improved. If feels like the car woke up a little.

Now the strange part.

My Bonneville has had a single cylinder misfire that has been getting worse over the last couple of weeks. It would stumble under WOT, but the CEL did not flash and it did not throw any codes. My LS1M scanner will scan for misfires, so after I installed the new TPS I hooked up the scanner and went for a ride. No misfires. I scanned all the way to work this morning, including a few WOT'* up to 80 MPH, and not one single misfire.

All I did was change the TPS. How can that correct a misfire? Maybe it was just the temperature and humidity conditions this morning and the misfire will come back, but I don't think so.

Roy,

Good stuff. Wonder if replacing the TPS at 200k is a good preventative maintenance action.

Our car does the same thing except the RPM'* would go down to 0 and then back up. Replaced the TPS but still doing it. Any suggestions? We have replaced The MAF Checked all and I mean all the wiring. Even went as far to changed the PCM in it. It seems to effect the car more at lower speed.