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P0304 Misfire Code Repeatedly Appears on 1997 Chevrolet Lumina 3.1L Engine

Model: 1997 Lumina Fault Code: P0304 Posted: 2007-09-15 09:51

I recently purchased a 1997 Chevrolet Lumina equipped with a 3.1L engine. The vehicle exhibits a rough idle and poor performance at lower RPMs. A persistent P0304 diagnostic trouble code (DTC) indicates a misfire in cylinder #4. I've already performed several diagnostics: replaced the spark plug and ignition wire, verified that push rods are correctly installed (I suspect previous repairs may have reversed them), checked the injector connector, and recently replaced the cylinder #4 fuel injector. After the replacement, the engine ran smoother for about 10 minutes with the check engine light extinguishing momentarily. However, the misfire returned immediately, and the P0304 code reappeared. Given that the injector was replaced less than 10 minutes ago, I find it highly unlikely that the injector is faulty or clogged. What could be causing this recurring issue? Any insights from owners of similar models? Jason

Related fault codes
P0304
Comments (9)
Anonymous 2007-09-15 12:13

Perform a compression test — cylinder leak-down may be the root cause of the misfire in cylinder #4.

Anonymous 2007-09-15 12:28

I've been testing the throttle response and noticed that when I hold it at half-throttle or slightly lower, the engine cycles between revving up and dropping down every 2 seconds. After about three minutes of this behavior, idle stability deteriorates significantly — the engine either stalls or sputters severely. Once I release the throttle and allow it to return to idle, acceleration becomes inconsistent; the vehicle spits and sputters and fails to accelerate properly. The only persistent code remaining is P0304.

Anonymous 2007-09-15 13:35

Great point — check compression levels first. Also verify for vacuum leaks, which can cause misfires in specific cylinders.

Anonymous 2007-09-15 19:09

Consider the electronic ignition module — it may be degraded or burned out, leading to intermittent spark failure in cylinder #4.

Anonymous 2007-09-15 20:15

Does the engine have proper spark on cylinder #4? If not, that would explain the misfire.

Anonymous 2007-09-16 09:23

I haven't yet performed a compression test. I'm currently borrowing a compression tester and will conduct it this afternoon. The engine does show spark on all cylinders — which makes me even more puzzled by the recurring P0304 code after injector replacement.

Anonymous 2007-09-16 10:27

Could there be debris or contamination in the fuel rail affecting cylinder #4's fuel delivery?

Anonymous 2007-09-16 21:34

Problem identified: cylinder #4 shows only 30 psi compression. Anyone interested in purchasing a 1997 Chevrolet Lumina with this issue? Might be a good deal.

Anonymous 2007-09-17 13:59

Do I hear $10? $10. $10 going once, twice…