Engine Performance problem
2001 Saturn SC2 4 cyl Front Wheel Drive Manual 171000 miles
In the morning my Saturn starts and runs fine. It goes to about 1200-1300 rpms, but a little slower than it used to.
If I try to restart it after sitting for 2-3 hours, the engine starts, but the rpm's don't jump up to 1200 like they normally do. It starts but the fuel mixture doesn't seem right because it hesitates, rps fluctualte around 700-800 rpm, it runs rough and then quits.
To start it I have to depress the accelerator all the way to the floor and recrank the engine. It then starts with the engine running rough for a few seconds before running normally. When I do this I also noticed black residue coming fromn the tailpipe on the ground.
It seems like the mixture at startup is too rich, which causes the engine to fllood (black residue from tailpipe). I just changed spark plugs and ignition coils with no improvement. One started, the car runs great.
Sounds like a bad coolant temp sensor that's what controls ur fuel mixture at differnt engine temps. They go bad and read colder then actual temp so when the car is hot it makes the engine run way to rich. It's screwed into the head with two wires going to it a yellow one and a black one. Make sure the engine is cold when u change it u will loose coolant. Also inspect the connector going to it if it's corroded then u will have to change the connector too. Make sure u get a brass tipped one the plastic tipped ones crack. That's what I would start with there only like 10. Let me know how it goes and if u need anymore help.