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Engine sluggish and backfires at idle/low rpm. Any ideas? Have tried lots already! 700 1991

posted by  rbb_in_oz on  Wed Jun 13 06:23 CST 2012
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last visit: Thu Sep 25 01:30 CST 2014
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Hi,

I drive a 1991 740 B230FB (normally aspirated) Station Wagon. It is a dual-fuel vehicle running on LPG most of the time. To ensure that the Petrol seals and injectors stay functional I run the car on Petrol (95 Octane) a few days a month.

However, during these days when using the normal Petrol ignition/injection system that the engine was made for, I am experiencing a very rich mixture. The onboard diagnostics continue to report an error code "engine too rich".

I have replaced the Lambda sensor and the Air Mass Meter. I have also run vacuum diagnostics which reveal that all is well in that area. I have, just in case, replaced all the vacuum lines. I have also replaced the Fuel Pressure Regulator, which isolates the mixture from fluctuations due to accelerator input (which is my understanding :) ) .

The only idea I haven't tried is to test the injectors for leaks which would cause an inbalance in the Bosch computer management which could be causing the rich mixture.

My question is:

Have I done everything that all you 740 experts would have tried?

Thank you to all for your help,

Cheers
rbb_in_oz






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