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2001 Sable 24 Valve Duretec P0302 Cylinder 2 Misfire - Idle Issues and Diagnosis

Model: 2001 Sable Fault Code: P0302 Posted: 2010-01-29 09:48

My 2001 Sable with the 24-valve Duretec engine runs smoothly on highways but struggles to idle consistently. It occasionally idles perfectly, yet most of the time it's unstable. I've already replaced the upper and lower intake gaskets, spark plugs, wires, coil pack, and fuel injector for cylinder #2. Despite these repairs, the P0302 misfire code persists. The issue seems intermittent—why does it occur sporadically? What could be causing this variation in behavior? Any reliable troubleshooting steps or diagnostic tests to identify the root cause?

Related fault codes
P0302
Comments (4)
Anonymous 2010-01-29 16:46

A burnt valve is a common suspect for cylinder-specific misfires, especially in older Sable engines.

Anonymous 2010-01-30 20:33

Performing a compression test or leak-down test can help identify if any cylinder has significantly reduced compression, which may be contributing to the P0302 code.

Anonymous 2010-01-31 10:19

Is valve burning common in 2001 Sable Duretec engines? What factors could lead to this—such as fuel mixture issues, oil or antifreeze ingestion, or exhaust leaks? Could an electrical component be the source given that the misfire isn't consistent? How much compression loss is typically required to trigger a P0302 code?

Anonymous 2010-01-31 13:56

Burnt valves are indeed frequent in these engines. Causes can include improper fuel mixtures, oil or antifreeze ingestion, exhaust leaks, or overheating. While a 20% compression loss is generally enough to generate a misfire code, actual results vary. A cylinder leakage test provides more accurate diagnostics than a standard compression test.