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1998 BMW 740iL Question: Misfires and loss of power

 

Question

Apollo13, Arlington, TX, June 23, 2010, 07:27
 Rookie

The car has around 83k miles, I've taken the car to a mechanic a few months back and he pulled the codes as P170 and P173 only. So I changed the O2 sensor on passenger side and MAF. Thinking this would clear the SEL. when it did not, I got my own OBD2 reader. I found the P170 and P173 along with P300, P305, P306, P307, P308 I cleared the errors to see what errors would come back, and when the SEL came back on, these are the errors showing now, multiple misfires on cyl 5,6,7,8 and P300 (repeat)10 errors showed back up. So I changed spark plugs and ignition coils from cyl 1,2,3,4, and put them on cyl 5,6,7,8. to check and see if the misfires would follow. I cleared the codes again, and when I rev up the engine to 4000rpms, the errors came back. I'm still getting the same error codes on the same cylinders 5,6,7,8. Don't understand why only on the right side cyl? What would cause misfires to just those cyl.? I would think a vacuum leak, or fuel pressure regulator would cause all cyl. to misfire. I'm at a loss of what could be causing the problem. Please help.
-Apollo.

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  • Answer #1

    Bret Bodas from RepairPal Test Shop, June 23, 2010, 09:57
     Master

    Apollo,
    This is odd. I would check the wiring diagram to see if all the coils or injectors on that side of the engine are controlled by a relay, or if they all share a common power source or ground. Check for anything that can have an effect on just those cylinders and not the others.

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  • Answer #2

    kanokla327 August 13, 2010, 13:13
     Rookie

    I have this exact same problom. Did u find out what was causing it? please let me know if u did im about to pull my hair out. lol

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    snow 70, January 01, 2014, 14:31
     Rookie

    I have the same car same problem. It doesnt make sense. Please let me know if you find a solution.

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