I have a 1997 3.5L Dodge Intrepid that the engine wants to surge at about 1000 RPM regardless of the gear it’s in. When the car is in park it doesn’t surge, the RPM stays steady. I have replaced the TPS sensor. I also had the fuel preasure checked and it is normal, 40 - 48 PSI. There are no codes in the engine CPU and no codes in the transmission. I have had this car to three mechanics and all hav been unable to fix the problem. This car has 198,000 miles on it and I really hate to put a lot of money in it.
Well, this is a bit of a poser. If it was a problem with one of the usual suspects (idle air controller, throttle position sensor), the surging would also occur with the car in Park.
WAG: Worn engine mounts are allowing the engine to pull on a connection, perhaps a vacuum fitting, that is in turn causing the surging.