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84 633 warm start issues

Discussion in 'E24 (1977-1989)' started by eric266, Feb 2, 2009.

    eric266 guest

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    I'm trying to sort out an issue I have been having with my 84 633. I just bought the car in its current non running state. I fixed the no starting at all problem (new ignition switch) After changing the cap and rotor, plugs, and coolant temp sensor i can still not get the car to run after it warms up. It will cold start and idle at 1200 RPM but as the car starts to warm the RPM will slowly drop and then it will run rough, backfire and die. Then it won't start again until I let it sit overnight. I did take apart the idle control valve and clean it and the car seemed to run longer before it started to die but it still dies. Anyone know how to check the idle control valve or anything else I should check??

    Thanks
    Eric
    74 3.0 CSi (euro)
    84 633 CSi
    90 325Ic
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    mooseheadm5

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    The procedures for checking the ICV can be found in the Bentley E28 manual. This has the infamous green box and associated finicky ICV. First, though, I suggest checking for vacuum leaks under the intake manifold, since the lines cannot be seen, but can easily rot off from oil exposure.
    Another thing, though. If you cannot get it to restart, there may be a temp related problem with an electronic part completely unrelated to the ICV. I have seen ECUs do this sort of thing. The quick way to test this is to make it so you can easily pull the ECU, run the car until the problem surfaces, then pull the ECU and throw it in the freezer. As soon as it is cooled down, reinstall and try to restart. If it works without having to wait for a long time, there is your problem.

    eric266 guest

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    Thanks Paul, I did not know about the green box! The car has been sitting for almost a year and I have cleaned all the connections but the idle control module, I will find it and clean the contacts to start with. Then check the ICV for proper operation. I did change out the lines under the intake manifold because they were oil covered and loose.

    Eric
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    RonnHale

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    Almost sounds like you bought my '84 633. We did what you did plus tried another brain, airflow box, put a resistor in-line by the temp sensor (from an old service bulletin), replaced idle control valve and module, cleaned the fuel injectors, performed leakdown test of fuel injectors, added a variable fuel pressure regulator, and a few other things that I've forgotten from 14 years ago. I remember our next step was the in-tank fuel pump. Talking to other Coupe owners (and shop owners) years later, the fuel pump always seemed to be the common point that they mentioned after I described the problem. We never tried it because after spending $$$$$ trying to fix it, I didn't want another part tried if I couldn't return it. So, I sold the car instead with the hot-soak starting problem still intact. I don't know if it's the solution, but if you can find someone that has a good one and will let you try it, you can see if that does the trick.

    eric266 guest

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    I have tried all that and more! The entire ignition system is brand new now!! I rechecked all the ports on the ECU and today I could not get the purge control valve to check out. I did some research in my Bentley manual and BMW had issues with those valves. According to the book BMW issued and field fix to reroute the vacuum lines and remove the valve. I have not had any luck finding a diagram on how the lines were rerouted. I did bypass the valve and the car runs better then before but it is still rough at idle and backfires when I first give it gas but then smooths out at 15-1800 RPM. I going to buy and new purge valve but I'm still on the lookout for the factory fix to reroute the vacuum lines!!

    Eric

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