Try accelerating in reverse.

We had the same issue with our 745 - it refused to accelerate going forward but would in reverse.

I found a bad pin on the air mass meter - the pin was pushed back into the plug and the wire loom to it wound around the power steering reservoir. When I tried to accelerate the weight of the loom moved it and it became an open circuit.

Look at the plug to see if one or more of the pins are pushed back. I was told that this was not uncommon.

I had to push the pin out and bend the lock tang a bit to help it stay in place.

I pushed the boot on the plug back and made a marker line across all the wires when they were in their proper place. That way, I could fold the boot back and check the connection after the plug was in place.

I also moved the loom to the front of the reservoir so that it pushed toward the AMM and did not try to pull away.

It did happen again after a service, so I put a tag on it to warn a tech about the problem.

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'96 855R,'64 PV544 driver, '67 P1800 basket case, '95 855, '95 854, the first three are mine, heh, heh, 485,000 miles put on 9 bricks