The problem is that the engine fires and then the revs reduce rapidly and the engine stalls.On examination plugs 1 & 3 are deluged in gas, 2 & 4 are sooty. To try and restart the engine at this point is pointless only resulting in excess gas in the cylinders and sump. I have changed the injectors around, but injectors 1 & 3 are still delivering excess gas. An interesting point I have discovered is that injectors 1&3 are fed by the same electrical wire, 2 & 4 by another, all having the same return. I have read on this forum that the ecu a Bosch DME unit, can be exposed to water in its compartment. On examination I found no trace of water contamination and the compartment was dry.
I have presumed that the fault may be with the ecu or units that influence it, therefore I have not looked at the O2 sensor, as I believe that this kicks in at operating temperature. Also I have not checked the cam and crankshaft sensors as the engine fires and runs. Plugs are delivering a good spark.
Several weeks prior to this fault occurring I changed the fuel pump and filter. Also I have changed the air inlet hose. I am pretty confident that it is not a vacuum leak. I have bench tested the temp. sensor and it is working, The MAF sensor, in this case of the vane airflow meter type, gave the following volt readings. It is a 5 pin connector with the pins numbered. 1 no volts (ground?); 2 4.99v; 3 0.41v;
4 4.55v; 5 4.99v. I have not checked the MAP sensor. The fuel regulator appears OK, no fuel in the vacuum pipe. If it was at fault I presume the fault would manifest itself in all injectors. The battery is good. The idle control valve is shot. I obtained a replacement from ebay, and of course it was the wrong type, 3 pin as opposed to 2 pin on this model. On failure the valve does not close completely, allowing a rough idle, as is the case here.
According to the manuals, with a failure of any of the influencing sensors, the ecu switches to "limp home mode" this is not happening. Also the vehicle does not have a check engine light. I have read that by depressing the gas pedal a certain number of times, you could obtain a blinking light, which relates to various fault codes, this does not happen here either.
The vehicle has been in the local shop but they were of not much help. To tow it to a BMW shop and have it analyzed would quite frankly cost more than the vehicle is worth. I am reluctant to scrap it, as I feel the fault is a basic one.
Has anyone experienced a similar problem? Can I swap the DME unit? The ignition is a simple key operation, and I am not aware of any immobilizer. Am I putting too much emphasis on the fact that 1 & 3 plugs are fouling. Any suggestions gratefully received.