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Thread: Need help with diagnosis

  1. #1
    Join Date
    Sep 2013
    Location
    Orlando, FL
    Posts
    1
    My Cars
    2003 BMW 325i

    Unhappy Need help with diagnosis

    I need help. I am not mechanically inclined but I'm learning. I have a 2003 BMW 325i SULEV, M56 engine.. I started having issues with the car not running smoothly, it had a like shake and didn't ride as smooth as it use to. I took it to my mechanic and he changed the MAF sensor. It rode better but I still had the shaking. I took it back to the mechanic because the service engine light came on. He checked the codes and it read that the O2 sensor was bad so I got a new sensor and the car ran worse than it did before. I changed coils 4,5 and 6 because the codes read they were bad coils. Those coils were switched out and the car ran smooth until I tried to accelerate. I had no power when accelerating and the misfiring and bucking continued. My mechanic switched out the three coils again and I still had the same issues. I changed all 6 spark plugs, I put in NGK (3199) and 6 new coils (OEM). The car runs a little better but I still have the misfiring and bucking, I have no power when accelerating and my oil light flashes red when I'm idling. Could it possibly be my engine ignition wiring harness? I tested each coil after I replaced them and they all had a reaction except the 6th coil. I replaced that coil with 6 different coils and I still got no reaction when testing it. I few years ago I made the mistake of taking my car to the dealer because it shut off on me while I was driving, luckily I was exiting the highway. The dealer told me my wiring harness was bad but they did something to fix it. Didn't have any issues with that until now. This car is in excellent condition except for this issue. My other issue is if it is the wiring harness, finding the correct harness for my engine. I have the M56 engine (SULEV) and I'm having a hard time finding this part. Does this sound like a wiring harness issue or should I throw in the towel and get another vehicle? I forgot to add that I also took the vehicle to Firestone where they tried to tall me into new plugs and coils. They told me I needed Bosch plugs instead of the NGKs and new coils. I told them thanks but no thanks.

  2. #2
    Join Date
    Dec 2013
    Location
    Chicagoland area
    Posts
    4,372
    My Cars
    EXOTICS
    Your symptoms either suggest an intake leak,
    which a pro smoke test can pinpoint and confirm,
    Or possibly a failing fuel pump/filter,
    which a fuel pressure test can confirm,
    by observing readings with a fuel pressure gauge.

    You have quite possibly purchased replacement parts needlessly,
    stay away from that Firestone, and find a reputable BMW specialist shop.
    This is an example of when membership in BMWCCA,
    or previous contact with a BMW enthusiasts club, would be most helpful.
    Last edited by MIKYZZ4; 04-30-2017 at 09:16 AM.

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