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Nissan Altima 2.4 P0304 Code: Diagnosis and Troubleshooting Guide

Model: nissan altima Fault Code: P0304 Posted: 2014-07-30 11:14

Hello, I'm experiencing a P0304 diagnostic code on my 1997 Nissan Altima 2.4L engine. I've already replaced the spark plug wires, distributor cap, ignition rotor, ignition coil, fuel injectors, and intake manifold gasket, as well as checked the crankshaft position sensor. Despite these repairs, the P0304 code persists. I'm looking for further guidance on how to properly diagnose this issue. Any insights or recommended next steps would be greatly appreciated.

Related fault codes
P0304
Comments (7)
Anonymous 2014-07-30 11:20

What model year is your vehicle? Is P0304 the only code present? Have you verified spark at cylinder #4? What's the appearance of the #4 spark plug—wet, dry, black, or tan? I recommend performing a compression test to rule out mechanical issues.

Anonymous 2014-07-30 11:59

It's a 1997 Nissan Altima. I've completed the compression test and all cylinders show readings above 150 psi. The #4 spark plug appears slightly black at the tip, which suggests incomplete combustion but not necessarily a faulty component.

Anonymous 2014-07-30 12:05

did you confirm spark at #4 plug?

Anonymous 2014-07-30 12:13

Yes, I have verified spark at cylinder #4 using a spark tester.

Anonymous 2014-07-30 13:20

Given the symptoms, something is likely missing. Have you checked live data with your OBD2 scanner? Is P0304 the only code displayed—does your scanner show all stored codes? Cylinder #4 is located on the driver's side, outboard position. Are compression readings within ±10 psi of each other? Has cylinder #4 been confirmed to fire using a removed and grounded plug test? Have you tried swapping fuel injectors or spark plugs? Did you use a noid light to verify ignition coil pulses? Could there be a vacuum leak—try the old carburetor spray method as a diagnostic tool? Any signs of oil consumption?

Anonymous 2014-07-30 13:29

If possible, swap the spark plug wire and fuel injector tubes. If the P0304 code moves to the new location, it may indicate a faulty tube or wiring issue. A recent TSB suggests that tube-related problems can trigger this code—let's test this hypothesis.

Anonymous 2014-07-30 20:34

kev2 wrote: If possible, swap the spark plug wire and fuel injector tubes. If the P0304 code moves to the new location, it may indicate a faulty tube or wiring issue. A recent TSB suggests that tube-related problems can trigger this code—let's test this hypothesis. I've already swapped both the spark plugs and injectors, with no change in the code behavior.