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1989 740 Turbo, fouls one cylinder 700 1989

posted by  dug on  Wed Jan 29 00:34 CST 2003
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I have an 89 740 turbo that is running poorly. The engine is freshly rebuilt (about 10k on it now) and the turbo is brand new (well rebuilt but just purchased). The old one failed and was sucking oil under decel. The car idles poorly and seems to lack power. Cylinder #3's spark plug is black (rich) while the rest of the plugs look perfect. I was hoping someone might know of a cause for this. Any ideas?

Thanks!
dug








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    1989 740 Turbo, fouls one cylinder 700 1989

    posted by  john sargent on  Wed Jan 29 06:08 CST 2003
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    last visit: Wed Oct 22 09:07 CST 2014
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    If the plug is oil wetted, the intake valve guide seal on that cylinder could have come loose. I have seen this happen on a VW where the valve guide seals were not fully seated on the guide.








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    1989 740 Turbo, fouls one cylinder 700 1989

    posted by  dug on  Wed Jan 29 02:23 CST 2003
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    Thanks Randy, I should have mentioned that I have aready replaced the plugs, changed the wires and swapped the injector. None of this seems to have changed anything. The only thing I have not yet tried is replaceing the intake gasket and checking the intake for cracks.

    dug








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    1989 740 Turbo, fouls one cylinder 700 1989

    posted by  rstarkie on  Wed Jan 29 02:14 CST 2003
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    I am always looking for the cheap diagnosis/fix. I would first swap #3 plug for another one. If #3 cylinder's plug still showed rich condition I would swap #3's plug wire. If #3 still showed rich and I am guessing it will I would then swap out #3 injector with one of the other cylinders and expect the rich running condition to follow the injector to which ever cylinder it is residiing in (bad injector). At least it won't cost you anything to try this and it just might point the finger at what is wrong.

    Randy







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