My 87 300e engine starts to cut out at exactly 4,000 rpm when driving, yet will rev beyond that point with the clutch in or in neutral.

From searching previous posts on this subject, it appears that the fuel pump relay is cutting power to the fuel pump at this point, which I have searched for information on.

In previous posts I have seen the Hall effect sensor identified as the unit which would determine whether the car is in motion, which should remove the rev limiter. However, my car doesn't appear to have a Hall effect sensor mounted on the back of the speedometer, and as it does not have cruise control or ABS, I'm told it would not have this sensor fitted.

Having checked the wiring diagram, I see there is an Overrun Cutoff Microswitch attached to the FPR, which would seem to be the likely culprit.

Can anyone tell me where to find this switch and how to check it is working correctly? If it was connected in reverse, would this cause the rev limiter to cut in when in motion, instead of in neutral?

If the car does have a Hall effect sensor and it is mounted somewhere else on this model, where would I find it?

I have already cured a rough idle/stall problem and in the process have replaced the following: FPR, OPV, 6 x injectors, Fuel Accumulator, ICV, rotor and cap, plugs, fuel filter, vacuum hoses, AC relay and checked the Air Sensor Pot which I believe is sending out the correct signals.

Hoping for help on this as otherwise the car is running great.