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1990 740gl non-turbo SOHC Hunts up and down in RPM while holding staedy throttle 700

posted by  Vulcan66 on  Sun Oct 21 21:32 CST 2012
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last visit: Mon Oct 22 21:28 CST 2012
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Still chasing this problem on my 1990 740GL non-turbo that has 250k on it.

Car starts right up, idles fine. Hold the accelerator down slightly to add a steady amount of throttle and the engine starts to hunt up and down in RPM.

Things I've checked or done.

Vacuum leaks
cleaned IAC valve
replaced TPS and adjusted switch
cleaned throttle body and new gasket

A while back (maybe a year ago) replaced in tank fuel pump)

kind of starting to suspect the catalytic converter being plugged. On one of my last trips with the car, the fiberglass packing started unraveling out of the tailpipe. Assume that was the packing from the muffler and wondering if it was somehow related to something going on with the catalytic.

My next move was going to be to remove the exhaust test port located ahead of the converter to see if the problem is resolved with the test port open.

Please, if anyone can help with this I'd be grateful. I really like the car and would like to see it on the road again.

Thank you





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New 1990 740gl non-turbo SOHC Hunts up and down in RPM while holding staedy throttle [700]
posted by  Vulcan66  on Sun Oct 21 21:32 CST 2012 >


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