Re: 84 745i Fuel Problem....HELP..... (archive)

If this is a Motronic car, I'd suspect the aux air valve - they clog up with carbon. (Not sure if 745i's came with this, but the regular 3.3 & 3.5s did). It looks like a cylinder with 2 connector. First WHACK it with a big screwdriver or wrench, then clean it with carb cleaner.

Changing the 02 sensor is not a bad idea. I would not remove it unless you also de-install the piggyback electronics that allow the 02 sensor to control fuel mixture. Cheap 02 sensor - 86 ford mustang 5.0 - its made by bosch in germany, and is about $35 at autozone.

Is it running very rich - can you smell gas? If so, you could have a bad coolant temp sensor. Blue or white connector on top of the thermostat housing. Sometimes they put a small resistor inside the boot of the connector. Peel back the rubber, and see if this is still connected. I've had the solder break on 2 different cars.

Samir.

My 745i is running rough. I suspect that it might be the O2 sensor. It looks very old and bad. I thought I read somewhere that these cars originally didnt have O2 sensors and when they were DOTEPAed O2 sensors were added. I disconected my O2 sensor and now the car wont stay alive. my O2 sensor has a single wire.
I want to know if the car will run better without an O2 sensor. please help me out. Before i disconected the wire the car would sometimes start and it would rev very low with a rough idle and die.

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