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Thread: CTS V P0305 Engine Misfire Code

  1. #16
    04SilverV is offline Cadillac Owners Member
    Automobile(s): CTS-V
    Join Date
    May 2009
    Age
    38
    Posts
    70

    Re: CTS V P0305 Engine Misfire Code

    I've always had a slight mis at idle but never a code and I suspected maybe a bad valve. That all changed recently when I installed a cam... Code P0300. Oddly enough when I was changing the valve springs I noticed that the first cylinder on the pass. side didn't pump up with air right away like all the others when I put 100psi to it (I actually used my leak-down tester to charge the cylinder). That cylinder took about 10 seconds or so and I could clearly hear the air coming from the throttle body especially when I opened the plate!
    Other than that I haven't ever done any tests like leakdown or compression. My mis is very very slight which most don't even notice, I think with the cam it's just now more pronounced for the PCM setting the code off.

    Although it's not a clear cut answer maybe it's a lead for you.

    Btw, I've got 73k miles on the clock and I bought the car with 30k bone stock.

    John

  2. #17
    jshaw is offline Cadillac Owners Member
    Automobile(s): Cadillac
    Join Date
    Oct 2008
    Posts
    9

    Re: CTS V P0305 Engine Misfire Code

    After much more diagnosis, I am still having this problem. Leak down tests, used engine block tester, cut open the wiring harness to find any problems, etc.

    Brought it to the dealership and they said I needed a new computer. Got a new computer, still the same problem.

    It was suggested that I swap o2 sensors on the front bank, but I can't see a good way to get to them. I have been searching on this forum, but can't find it mentioned. Anyone know a good way to get at the front o2 sensors?

  3. #18
    jshaw is offline Cadillac Owners Member
    Automobile(s): Cadillac
    Join Date
    Oct 2008
    Posts
    9

    Re: CTS V P0305 Engine Misfire Code

    I found the problem. The roller on one of the lifters on cylinder 5 was galled.

    I just wanted to post in case someone else goes through these issues.

    Now I have to figure out what kind of cam to put in. Any suggestions? I really don't want to have to put on headers and all that stuff, but might as well get some more power out of it.

  4. #19
    heavymetals's Avatar
    heavymetals is offline Cadillac Owners Master
    Automobile(s): 05 maggied CTS-V, 03 maggied Z06
    Join Date
    Nov 2004
    Posts
    8,788

    Re: CTS V P0305 Engine Misfire Code

    Use Morel lifters.

    You won't regret it.

  5. #20
    darkman's Avatar
    darkman is offline Cadillac Owners Master
    Automobile(s): 2005 CTS-V
    Join Date
    Nov 2005
    Location
    Spring, Texas
    Posts
    8,207

    Re: CTS V P0305 Engine Misfire Code

    I would call Geoff Skinner with Engine Power Systems. Geoff can set you up with an EPS-lobed cam designed to get the most power out of an otherwise stock engine.

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