RPMs are stuttering/surging at highway speeds, check engine light code was for the coolant sensor. I replaced it but the surging is still happening. The wiring didn't look fabulous, I put a little electrical tape around a spot by the sensor so I don't know if maybe the wiring is bad. A mechanic told me to replace the thermostat. Any other suggestions? Thank you so much in advance for any assistance.

Bryan

UPDATE: Replaced the thermostat but nothing changed. Transmission fluid was low so I added some still no change. I think there may be a fluid leak, will investigate more tonight. The surging only seems noticeable at highway speeds when I ease up off the gas, on cruise control it's very obvious.

 

check fuel pressure? spark to each cylinder wire successful?
check wiring on coolant sensor routing back. a misfire was fixed on this board by someone else who noticed bad wiring with that sensor.

 

Thanks for the response. It did seem that the wiring wasn't great when I replaced the sensor. Had a new fuel filter and pump installed 2 years ago but haven't recently checked the fuel pressure or cylinder sparks. I did have a random misfire code pop up last time I took it in to get tags but it never came back after it was cleared a few months ago. I will see if I can figure out how to check all that and go from there. Thanks again.