Try the coolant temp sensor. On the cylinder head, near the rear. This is the one with two connections to two different wires. One for the fuel ECU, one for the ign module. Both terminals should show a resistance to ground. This varies with temperature. If one side is open to ground, try switching wires for a temporary fix. The fuel is much more sensitive to temperature than the ignition is. If the side presently on the fuel side is open (broke) it's telling the engine you're parked in the Arctic when the engine is really warmer. Result: too much fuel. It made a dramatic difference on my '87 260E.

Good luck,

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Norm in NJ
Next oil change at 230,000miles