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Update on 84 633 start issues

Discussion in 'E24 (1977-1989)' started by eric266, Mar 22, 2009.

    eric266 guest

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    I finally resolved some of my no start / warm start issues and thought I would pass on what I found as it may be of use to someone else in the forum.

    The car had sat for almost a year before I purchased it so it had bad gas, corroded grounds and connections which were all cleaned up first. Then came the troubleshooting:

    1. The ignition control module, very easy to check once I purchased the Bentley 5 series manual! Found a bad temp switch and a suspect idle control valve. changed both and the problem was still there all though not as bad.

    2. Checked the ECU found a bad position sensor, when I went to troubleshoot the connection to see if it was the sensor or wiring I found that the PO hard wired the sensor in!!! I can not for the life of me know why he would do that. Upon inspecting his hack job I found more corrosion on the splices. cleaned it all up and wouldn't you know it the car starts every time all the time!!

    I still have a rough idle along with what sounds like a knock, and a little bit of back fire under load but I'm hoping between the bad gas and the full tune up she will get in the next week or so that should fix it. I'm going to change out the plugs, plug wires, fuel filter (again) cap, and rotor.

    Thanks to Paul and everyone else on the list that help me get the old girl running.

    74 3.0CSi (euro spec)
    84 633CSi (finally running...)
    91 325i
    • Member
    • Technical Service Advisor


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    The PO wired it in because the connectors on the sensors disintegrate over time. Glad you found the problem!

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