I have one for both of you to try. I went through hell with my sister's 1990 740 Turbo. Locate the fuel injector relay. On the 91, it is over on the passenger side strut tower. Earlier cars have it on the driver's side, clipped to the power steering reservoir bracket. You will need to activate the relay and measure resistance across the connections to the injectors. If it is more than 1 OHM, you may have found your problem. A problem with this relay will act like a failing ECT, Oxygen sensor, Mass Air Meter etc. I know, because I just went through this myself.

I would check the wiring between the ECT and the computer, because, as you know, infinite ohms at this pin will cause the computer to think its absolute zero outside and pour gas into the engine.

Since this is an intermittant problem, be prepared to measure ECT resistance at the plug on the spot. Have your meter ready, the pins identified, the ECU cover pulled and the connector ready to remove so you can measure the resistance the next time it does it. In the meantime, you can pull off the plugs at the ECU and the ECT and extract the terminals and visually check the integrity of the pins and the crimps. Bend them to make tighter contact, and re-crimp/solder if neccessary. Also, consider doing the same to the harness connectors that exist in between; On my '87, the circuit goes through a connector near the right side of the firewall.

The ECT grounds through one of the brown wires attatched to the intake manifold. (at least on my '87) Check these, check battery ground cable, etc, make sure the ECT has a good clean path to ground. Consider adding a ground wire directly to the battery.

If you find the circuit open and you can't find a fault at a connector, I would run a new wire From the ECU to the ECT. Pins for the connectors should be available at the dealer.

HTH,
--
bagle, 87 745t

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