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e30 C191 MultiPlug

Various Roadfly Board Comments:

Consider checking the fuel injection harness (C191 multiplug). It contains wiring for the fuel injectors, dash coolant temperature and main computer coolant temperature sensor.

The infamous C191 multiplug is a 7 pin round engine wiring harness connector that is located directly beneath the throttle body. This connector is only present on 88 and later 325's. It connects the injectors, coolant temp sensor and the time delay sensor to the ECU. It is infamous due to a corrosion problem. There is a factory service bulletin to correct this problem. The fix is to cut a small hole in the C191 rubber boot on its lowest side.
That way water will drain out.

the C191 connector looks similar to the diagnostic plug connector. Remove air filter assembly and look under the intake manifold. Unscrew C191 plug, if it does not fall apart in your hands and there is no corrosion on the male/female terminals then it is not your problem. Otherwise you have found your problem.

I hope this helps you,
Alan Alfano
88 325iX

It can collect water, especially if the coolant pocket on the throttle body springs leak. Someone most likely spliced the wires instead of trying to put new pins on the existing (now shorter) wires - which is a real PITA. It is common enough for BMW to put out a service bulletin about this problem. The Red/White wire on the injectors should be battery voltage, when the main relay is activated.

Here's the voltage flow. From the positive terminal, through the main relay, through S112, through C191 (the connector mentioned above), through S120 and splitting into six wires and going into each of the six injectors.
From injectors 1,3,5, three wires go into S104, through C191 (again) and into the motronic unit (and ground somewhere after that). Injectors 2,4,6 are similar, but go into S106 instead of S104.

(Yes, if you want to get really technical, the flow "starts" at negative terminal and goes to the positive terminal on the battery)

Keith
www.e30ic.com

e30 Idle Faq - extremely thorough!