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Thread: Loss of power and code 1221

  1. #1
    Join Date
    Oct 2005
    Posts
    518

    Default Loss of power and code 1221

    Hello all!

    I just bought my first E34. Car info: 1990 BMW 535i Automatic
    I'm experiencing a rather unique issue with the engine. Whenever the engine exceeds 2500rpm under acceleration, the CEL comes on and the car looses power. The code is 1221, which points to the O2 sensor. If the engine is kept under 2000rpm, there is no problem at all. I'm inclined to think that this is an issue with ignition, particularly spark plugs causing an incomplete combustion, in turn alerting the ECU that there is an excessive amount of unburned fuel in the exhaust gases. The engine tends to have a problem during warm up as well. Has anyone had such symptoms with worn spark plugs? I've already purchased new plugs, but can't test my theory out until the car gets out of the paint shop. It may also help to mention that if I back off the throttle and let the car cruise at normal RPM, the CEL goes out and the engine once again has power. Thanks in advance for any help with this issue.

    P.S.: How often should the distributor cap and wires be replaced? I haven't been able to find any service information for these items in BMW documentation.

    P.P.S.: Did all E34 models come equiped with the tilting passenger side mirror? Mine does nothing when Reverse is selected (mirror control in driver-position).

  2. #2
    Join Date
    Jul 2004
    Location
    Kernersville, NC
    Posts
    186

    Default

    Tilting passenger side mirror is a 540i only feature, if I am not mistaken.

  3. #3
    Join Date
    Oct 2005
    Posts
    518

    Default

    My owner's manual lists models 525i, 535i, and M5. The same manual also describes the operation of the tilting mirror. I know my father's 735il had that feature.

    More development on the engine issue. The car passed the emissions tests but the Nox content in the exhaust seems to be borderline high. As far as I've been able to research, this is caused by unburned fuel. Looks like the spark plug/ignition system theory is being confirmed.

    P.S.: Great forum! I'll make sure to make a more formal photo introduction once I get my car repainted.

  4. #4
    Join Date
    Dec 2003
    Location
    Eastern Tennessee USi
    Posts
    14,839

    Default

    Could be a multitude of things, start by inspecting all of the intake hoses, tubes etc. You probably have a leak somewhere, then replace your plugs and crap and finally reboot the computers and see how good you did.

    Good luck Bro.
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

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