Hi folks I'm after some ideas. I have a 1981 244 with B23E motor, with constant injection system, bosch electronics in Australia. Has been running fine, using a little more fuel than usual my wife says. I can start it after a tough start, idles low but even. As soon as I depressed accelerator, it coughs, splitters and misfires, and will eventually stall. Every now and then I can start it and it will rev high for a while before slowly revving down and coughing spluttering and stall etc.

The fuel pressure seems fine, although I have no gauge to test. When line is pulled after filter, pumps large volume and high pressure. Fuel relay is not problem as I bypass and it is the same. New in tank pump six months ago. Filter fine. I took the bellows off, and when pump.is running and I lift the air flow plate manually, each injector gives a good spray pattern. I assume therefore that the fuel distributor is fine and injectors fine.

Timing is fine. New plugs. Leads test similar resistance and when tested each lead gives about 5mm minimum spark.

I cannot find any vacuum leaks or dodgy looking hoses. I visually checked every vacuum line around manifold and sucked air creating vacuum which held. New air filter.

I haven't checked fuel return line to ensure fuel pressure valve is ok, but thought this was just for start up to provide richer mixture when cold.

I am at a loss of where to go from here and would appreciate any help. I don't think the CI fuel injection system has MAF sensors or ECU units. When it revs the motor sounds great, but then gets bogged down. The plugs we're sooty and black, not straw coloured like when lean. It blows no smoke when idling.

Any help.would be greatly appreciated.
Dave

 

Have you checked to see if the MAF is clogged?

 

maybe that valve is something to check as from what you describe it appears clearly the engine is running rich when at normal operating temperature.

 

don't think an '81 has a MAF. Closest thing I've had is an 84 Audi with K-Jet which used an air metering plate that needs to be able to move freely to provide the intake airflow measuring. I suspect your car also has and idle air valve (again similar to my old Audi) - they can get gummed up so make sure its clean. They also buzz when working so you should be able to feel a small amount of vibration when plugging/unplugging with the ignition on. Did you check the injectors as well? they may be due a cleaning after 35 years or so - a simple start would be to run a can or two of injector cleaner. Finally, hows the exhaust system? Again like my 84, there's probably an O2 sensor which plugs into the upstream side of the cat. I'd guess its a single wire design and is used to provide the lamba feedback for the injection. If this sensor is dead, you'll likely run rich. The bad news is they can really get stuck in the cat (I had to drill mine out when replacing on the Audi). Make sure there's no exhaust leaks as well between the head and cat to throw off the sensor.