My 740 has developed a problem. The engine acts like it is running on two cylinders and has no power. Also the tach will not operate. I have replaced the flywheel sensor, the plug wires, the spark plugs, timing belt, fuel injection relay, the fuel regulator, the fuel injection ECU, fuel pump, temperature sensor, etc. The fuel injection system is a Bendix/Semmens and the ignition system is a Regina. The car also has 165,000 miles and most of the parts replaced while worn out were very close to being worn out. Anyone know whats wrong.

/// I don't have that model but there has been another recent post that found a bad connector in the power to the fuel and electroinic controls. This would cause sudden failure and the intermittent contact would act as if only two cylinders (or less) are firing.

Does any thing else act up when the engine is misbehaving, radio, wipers? Check the positive battery clamp. The positive system wire connection is inside that clamp and not visible. The same is true of the negative battery cable. Some FI systems will not run on the alternator output. Alternators can be noisy, the battery acts as a filter. When the battery is switched in and out of the circuit by a bad cable the ignition acts up. You can bypass the negative cable with your jumper cables. Use a short peice of house wire if the car is already running. Eliminate the positive system wire the same way. Rarely (very rarely) a defect inside the battery will cause this problem. Borrow one, do not buy a new battery to test since the battery is probably not the problem.

I agree with previous post, but you might also try some baseline checks like a COMPRESSION check. It's just possible a valve has gone south.

OTOH, it could just be a leaking clamp/hose somewhere between the AMM and the throttle body, or a dirty throttle body (generally just bad idle, not low power).

I didn't see rotor and distributor cap in your shopping list. How about pulling plug wires one at a time while it's running to see if you can narrow down a bad cylinder(s).

Our 740 with Regina was running a little rough and I smoothed it out considerably by removing the coil and power stage and cleaning-up all the mating surfaces (including the chassis attach points) and all the electrical connections.