I have a 2000 Saturn SC2 with 128k miles on it. Wife drove it home Friday. No start Saturday. It had become increasingly hard to start in the mornings. Occasionally it would nearly stall when completing a stop at a red light. The starter cranks with no problem. So far I have replaced the battery, fuel filter, spark plugs, plug wires, coils 2x(DIS with waste spark), ignition module, and crank position sensor. I have used a spark plug tester set at 25kV and checked all four plugs - spark looks strong and snaps in the tester gap. Fuel pressure tester right at the fuel rail says 55psi and does not drop while cranking to start. Tailpipe smells of unburned fuel after cranking though I have not used Noid lights yet to check the injectors. I’ve found no burned fuses - especially checking ign, fuel, etc. I have an OBD-II scantool but the ECU reports no error codes. Any help would be fantastic - I’m coming to the end of my diagnoses thoughts. Thank you CarTalk!
I would do a compression check. You may have a leaking head gasket.
Turns out this was an ECTS problem. The sensor was causing the engine to run too rich and flood the cylinders. The compression test came back with erratic readings - especially since it had been trying to start so rich and washing out the cylinders.