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Thread: Not another rough idle thread!!!

  1. #1
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    Not another rough idle thread!!!

    Yup, here we go ANOTHER rough idle post. Ive done some extensive research on this issue and after replacing several components i want to start documenting my progress somewhere and maybe get some insight from you smart guys and gals here at bimmerforums. So i just bought my 89 325ix and it had a rough idle problem. I replaced:
    6 injectors
    spark plugs(w8lcr) gapped at .028
    Crank case breather hose
    Fuel pressure regulator vacuum line going to manifold
    The purge valve line from manifold to the purge valve
    The line from purge valve to the charcoal filter
    Cleaned MAF
    Cleaned ICV
    Replaced CPS(csr wouldnt start at one point during all of this....the sensor was bad)

    The car has a rough idle only when warm. It doesnt seem to lose tremendous power (take that for what its worth)
    It idles around 800 when its warming up(tach, gas gauge are erratic) and drops down below 500 sometimes.

    M9st of the vacuum lines were replaced by vibrant vacuum hose which doesnt really seem rigid so idk if that has a factor in this

    The head gasket appeads to be leaking on the fron part of the motor by all of the coolant stuff

    No CEL

    I dont mind putting more money into this car to get it running right but im mechanically inclined but not a mechanic by trade so thats why im making this post. Any help would be greatly appreciated.

  2. #2
    richardodn's Avatar
    richardodn is offline Old Guy BMW CCA Member
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    The front oil leak is more likely the camshaft seal.
    You still likely have a vacuum leak. Any air that can enter the engine is a leak. For example a bad seal on the oil filler cap is a leak. The nipples on the throttle body can also come loose. (Epoxy them back in.) Does your check engine light ever come on when sitting at idle?
    I don't see an O2 sensor on your list. That's another likely culprit.
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  3. #3
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    Quote Originally Posted by richardodn View Post
    The front oil leak is more likely the camshaft seal.
    You still likely have a vacuum leak. Any air that can enter the engine is a leak. For example a bad seal on the oil filler cap is a leak. The nipples on the throttle body can also come loose. (Epoxy them back in.) Does your check engine light ever come on when sitting at idle?
    I don't see an O2 sensor on your list. That's another likely culprit.
    I did replace the oil filler cap with a new one

    I noticed before that the nipples on the throttle body are loose when I disconnect the lines to them. Could this be the problem

    The check engine light has not come on for any of the idle issues.

    It is a very slight rough idle like a small vacuum leak or something. The engine doesnt surge or act erratic.

  4. #4
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    Quote Originally Posted by BMWBurnout875 View Post
    I noticed before that the nipples on the throttle body are loose when I disconnect the lines to them. Could this be the problem
    Sounds likely from the info you've given. I also usually spread oil on the oil cap seal, like the oil filter one, if it's new or dry.

    Might be worth checking your engine temp sensor if that doesn't fix it.


  5. #5
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    Just wanted to throw in my 2 cents based on my experience with rough idles. A new DME can do wonders. If it doesn't have a 173, you should replace it anyway. Another culprit could be the AFM. When I replaced mine, I couldn't believe how well my car ran. This was after replacing all ignition components too. Both of these parts can be found as a reman, so they aren't too expensive.

  6. #6
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    Quote Originally Posted by hotdish View Post
    Sounds likely from the info you've given. I also usually spread oil on the oil cap seal, like the oil filter one, if it's new or dry.

    Might be worth checking your engine temp sensor if that doesn't fix it.
    Is that the sensor that is plugged into the top passenger side of the radiator?

  7. #7
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    No e30s, again :(
    no, that is the one for the fan. the engine temp sensor will be on the thermostat housing
    No e30s again.

  8. #8
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    Quote Originally Posted by superj View Post
    no, that is the one for the fan. the engine temp sensor will be on the thermostat housing
    Okay I'm just going to replace it since it's fairly inexpensive to do.

  9. #9
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    Quote Originally Posted by kingsalmon View Post
    Just wanted to throw in my 2 cents based on my experience with rough idles. A new DME can do wonders. If it doesn't have a 173, you should replace it anyway. Another culprit could be the AFM. When I replaced mine, I couldn't believe how well my car ran. This was after replacing all ignition components too. Both of these parts can be found as a reman, so they aren't too expensive.
    My DME part number from BOSCH is as follows
    0 261 200 351

    Also an update I cleaned the throttle body, MAFS and the ICV again just to be sure it was clean, also superglued the 2 fittings on the throttle body back in and it still didnt fix the problem.
    Last edited by BMWBurnout875; 11-09-2018 at 03:10 PM.

  10. #10
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    Just wanted to post an update on the progress so far.
    I just replaced the spark plug wires, distributor cap and rotor along with the coil.
    Also did the Engine Temperature sensor, deleted charcoal filter for the evap system.
    Car still has a rough idle.
    Last edited by BMWBurnout875; 11-17-2018 at 10:21 PM.

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