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Thread: Injector replacement

  1. #1
    New Member
    Join Date
    Jan 2008

    Default Injector replacement

    I am in the process of getting a tune from Blackbear performance. I was sent the flashscan and cable to get information from my stock set up. The scan read that my bank 2 trim levels were 16% higher than my bank one, but I had a miss on cyl #3. I replaced plugs and wires and PCV valve. The miss in #3 went away, but the DTC code of P0300 was still there. I am going to change all 8 injectors this weekend and hopefully that will cure the problem. But for some chance it doesn't cure it, what should I check next? Coils, fuel pressure regulator?

  2. #2
    Joe (Moderator) joecar's Avatar
    Join Date
    Apr 2003


    Sierra, welcome to the forum... ...I sometimes miss a few threads, I do apologize.

    If you still get unbalanced LTFT's, check for air leaks between heads and cats.

    If you get misfires, do these things:
    - change fuel filter and air filter;
    - clean MAF (use MAF cleaner, not brake clean),
    - do a CASE relearn (just in case you're seeing false misfires),
    - ohm your plug wires while wiggling them around, they should all be close, reject the one(s) that differ significantly (but see next test),
    - using a spark tester (looks like a spark plug with no ground electrode and has a grounding alligator jaw clip, available from AutoZone) test the output of each coil (should see bright fat spark),
    - observe plugs/wires at night in pitch darkness, if you see corona glow or arcing, then you're losing spark strength and misfiring,
    - measure fuel rail pressure with key on engine off (pressure should hold steady for a minute or so; if not then either injectors and/or regulator leak), then measure again with engine running (should be close to 58 psi and close to steady, if not then check fuel filter, regulator, pump) [AutoZone sells a $30-40 GM fuel rail compatible pressure gauge],
    - check all your grounds (look also behind the LHS head, and on either side of block).


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