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2002 Dodge Durango Cylinder 1 Misfire After Tune-Up - Check Engine Light & Diagnostic Codes

Model: Durango Fault Code: P0300 Posted: 2015-11-30 07:54

I recently completed a full tune-up on my 2002 Dodge Durango. It ran smoothly for two days, but then began exhibiting a misfire in cylinder 1, causing hesitation specifically between 35 and 45 mph. I replaced the spark plugs first—no improvement. Then I changed the ignition wires, distributor cap, and rotor—all without resolving the issue. I subsequently replaced the #1 injector, still no fix. Finally, I replaced the coil pack for cylinder 1, but the misfire persists. I've now reinstalled all components twice (plugs, wires, cap, rotor), and the problem remains. The check engine light is on, and I haven't yet retrieved any diagnostic trouble codes. I've also performed a compression test: cylinder 1 reads 75 psi, while the other cylinders show around 160 psi. No visible vacuum leaks were found. Given the age of the vehicle (180,000 miles), I'm wondering if this could be an internal engine failure such as a stuck valve, broken valve spring, or piston ring issue. Any advice on next steps would be greatly appreciated.

Related fault codes
P0300
Comments (7)
Anonymous 2015-11-30 08:08

Did the misfire start after the tune-up? How did you confirm cylinder 1 was specifically misfiring? Is the check engine light illuminated? Are there any stored diagnostic trouble codes? Could a vacuum leak be contributing to this issue?

Anonymous 2015-11-30 11:17

When I first purchased the truck, the plug gap was set at 70mm. After the tune-up, it ran well for two days with strong performance in the 5.9L V8 engine. Then the dummy light came on and the vehicle began running rough—no power or smoothness. My compression test showed 75 psi in cylinder 1 and approximately 160 psi in all other cylinders. I've inspected for vacuum leaks but found none. This leads me to suspect a stuck valve or internal engine component failure.

Anonymous 2015-11-30 12:41

This could indicate an internal engine problem—how many miles does the vehicle have?

Anonymous 2015-11-30 13:47

180,000 miles

Anonymous 2015-11-30 13:52

autojoe wrote: Internal engine problem... How many miles? 180,000 miles

Anonymous 2015-11-30 15:41

180,000 miles

Anonymous 2015-12-01 08:38

An internal engine issue is possible—definitely needs proper diagnosis. Potential causes include a burned valve, broken valve spring, valve train problems, or piston rings. Given the vehicle's age and mileage (180,000 miles), significant repair costs may not be justified unless confirmed by professional diagnostics.