I had previously posted the problem quoted below, but my I have more to share on it and have brand new problems popping up with the car.
"My 2007 Chevy Impala has developed a brand new problem today. Driving down the block to the store, the speedometer started fluctuating wildly. I was going a consistent speed of about 10 mph in my parking lot and when I braked to a stop the speedometer started swinging all over the place, from 10 to 35 mph. It then gave me a message on the dash saying “Speed Limited to 107 MPH” and somehow killed my accelerator because the gas pedal no longer did anything. I restarted the car and the accelerator worked again for a bit and then pulled the same problem again. The speedometer is now fluctuating wildly the entire time I drive, including while stopped, but so far the message seems to have kicked on and disabled my accelerator only when slowing to a stop and accelerating out of a stop (it happened three times).
I know that the Impala’s governor is set to 107 mph so I can guess why that message exists, but I wouldn’t think a governor would actually kill the car even if it kicked in at the right speed.
It wasn’t that long ago that we had to have our pedal position sensor resynchronized and the mechanic had mentioned that it was possible the sensor was going bad, but I don’t think that would be the problem here as it seems like the car would actually have been accelerating sporadically, whereas in my case just the speedometer is swinging around despite an even speed."
As an update to that problem, I took the car to my mechanic (a very good mechanic, but not a GM dealership), and he could not get the car to recreate the problem and the computer was not producing any error messages. As it had happened on a night that was especially cold and with freezing rain, my mechanic suggested that the cold/damp mixture may have caused the sensors to act up. A couple of nights later, in identical weather conditions, I got the exact same problem again, but not again since then (and we haven’t had the same weather again).
Now, the car has a brand new problem in addition. After driving about a mile from our home in the car, the temperature gauge shot all the way up to highest level, the thermometer light came on, and the car began alternating messages between “ENGINE OVERHEATING/AC OFF”, “ENGINE OVERHEATING, IDLE ENGINE”, AND “ENGINE OVERHEATED, ENGINE OFF.” I might be paraphrasing a bit, but that is how I remember them.
After parking the car for a couple of hours, it ran just fine for at least a few blocks.
A few days later, we used that car again for the first time. We drove a couple of miles with no problem, and parked for lunch. On our drive back, we got the exact same messages. Now, the coolant seems to be filled up to the right level, and the engine was not actually overheating. I turned the heater to full blast and the air was cool (it was 33 degrees outside and the Impala has always taken a long time to heat up). After telling me that it was reducing engine power, the car developed an unusual engine shudder. When I parked the car and opened the hood, it wasn’t even as warm in there as it would be on a normal day after driving for half an hour. The car apparently thinks it is overheated, though, because after I shut it down, the fan continued to blow despite the keys being removed.
I should also note that during this recent event, it also started telling me to change engine oil, and is indicating that my engine oil quality is at 0%, despite the fact that it was at 31% three days ago.
I don’t know if these are related, but sense my speed sensor seems to be feeding bad information now and then and apparently my temperature sensor is feeding bad information, and possibly my oil change sensor is feeding bad information now and then, it certainly seems like something is wrong electronically.
I called GM and was told there are no recalls or bulletins for the Impala, and of course they want me to visit a dealership but offered, at best, to try to get me a bit of a discount on labor.
Anyone have any ideas?