I just replaced the head on a 1997 Saturn SL2 due to it running rough and low compression on one of the cylinders. It idles very smooth now and has at least 160 PSI on all 4 pistons. The problem is that it surges as your are accelerating slowly, gets poor gas milage and it seems that the oil level is raising on the dip stick. I’m guessing that gas is some how getting into the oil. I checked the spark plugs for carbon build-up which would indicate a rich gas mixture but they’re clean (lite tan color). I also replaces some of the vacume lines where I found cracks, but I may have missed a few. Overall the car seems to run perty good. The problem is that this is my duaghter’s car who lives 10 hours drive away and I don’t want to stick her with any problems. I don’t want to take it to a dealership where they’ll charge me a lot of money but my mechanic that I normally deal with doesn’'t know what to do with it since there arn’t any fault codes on the computer. Any suggestions?
Check the Engine Coolant Temperature Sensor (ECTS) and it’s connector. This is a common failure on the Saturn that makes it run just as you describe. It’s the sensor with two prongs on the Pass. side of the head. You can also check over at SaturnSpot as they are nothing but Saturn heads.
If the warm idle is a little high, anything above 950 rpm, then check for a vacuum leak in the intake manifold gasket around the #1 cylinder.