I have a 1995 Pontiac Bonneville that runs great except when driving on the interstate at a steady 75 mph, the Rpm’s will jump from 2200 to 2700, sometimes 3,000 rmps, hang there for a while and back down again. When the Rpm’s change, you can feel the car jerk, but the speed remains the same.
Also, the cruise control won’t work when at the higher rpm’s, which is where it mostly stays, lately. When it drops back down, it’s only for a few seconds. IF I manage to get the cruise control to set during that few seconds, it will stay at 2200 rpms, and obviously my gas mileage is better. But it will suddenly “surge” occasionally and disengage the cruise control. I have to wait, sometimes for many miles for the rpm’s to drop again.
What could be wrong? The previous owner said they had the same problem and changed a very dirty fuel filter and the problem stopped. I don’t know when they had it changed but the problem has been there since I bought the car. Thanks for any advice.
Have you changed the fuel filter yourself after knowing this?
Another problem may be a loose or broken TPS.
A broken or loose Throttle Position Sensor can cause intermittent bursts of fuel from the injectors and an unstable idle because the PCM thinks the throttle is moving.
I haven’t changed the fuel filter yet, because I’ve only had the car for a month, and it was my understanding that they just recently had the car completely tuned up, plugs, wires, oil change and fuel filter.
I know a little about cars, and I had a Chevy Blazer that was guzzling gas would idle fast because of a bad MAP sensor or TPS, (we changed both). So, I was more suspicious of a sensor problem than a fuel filter.
Also, the car idles steadily, and the problem is unnoticable at lower speeds.
I would consider changing the fuel filter.