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  1. #1

    Join Date
    09 Oct 2019
    2008 9.3 - 2004 9.3 AERO - 2006 9.3 AERO
    Thumbs Up:   0

    P0304...I'm Stuck...Please help!!!

    I just brought my 2006 Saab 9.3 Aero with the 2.8 liter 6 cylinder turbo (126,000 miles) into the shop because the check engine light came on and it has been running fairly rough since. The shop who specializes in Saab repair used a Tech 2 diagnostic scan tool and found a P0304 cylinder #4 misfire. Below is the list of diagnostic testing that was performed.

    **Remove and replaced coil on cylinder#4 which was in two pieces.
    **Moved plug to adjacent cylinder and misfire stayed in cylinder#4
    **Number 4 injector is shut off after 30 seconds via engine computer to save converter from damage.
    **Completed injector volume test to confirm even fuel displacement on all cylinders.
    **Checked for sticking injector using stethoscope and found to be fine.
    **Test drove while watching live computer data. MAF, fuel trims, etc...All normal...MAF 7-145 gr/sec
    **View valves fully opening and closing using digital baroscope inside cylinders.
    **Vacuum test shows low vacuum 10-13" mercury.
    **Compression test normal @ 150-160 all cylinders.
    **Perform running compression test - slightly low readings on front bank of all 3 cylinders.
    **Catalytic converter is not plugged.
    **Cam timing is proper.
    **Performed a smoke test on intake to check for vacuum leaks.

    Mechanics notes:
    " I was initially suspecting a faulty ECU but now believe there could be something internal going on but not sure at this point."

    Has anyone experienced this issue or know what my next step should be. Did the mechanic miss something or possibly overlook something that could be the culprit. Would an engine tear down be the next step? The engine starts up great and sounds normal and does not make any noises that would indicate something internal would be wrong, i still drive the car and it really only misfires under acceleration and hardly noticeable at idle. Please help!!! Any advice would be greatly appreciated.

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  2. #2
    Saab Fan
    Join Date
    05 Oct 2017
    Saab 9-3 2006 2.8 Turbo V6 Hirsch
    Thumbs Up:   0
    Change your boost solenoid. Change your spark plugs. I have iridium ngk and gap your plugs at 0.8mm. This is a cheap beginning but it helpt a lot. Had same prob. I also changed 2 coils. Oh the low vacuum, check the lines near the ecu.

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