1985 760 Turbo

I am still trouble shooting a rich running engine, but have made progress so far with the help of all of you on the board - many thanks as I have learned a lot but have some questions I would like to offer anyone interested:

1. I am not sure yet how the throttle position switch can effect fuel mixture -if it does. can a failure here effect the AMM?

2. Can an injector impulse amplifier be sending too weak a signal and cause a low spark? If so can I measure the spark jump with a spark tool (I have) to see if I am getting enough burn from my plugs?

3. It When I unplug the AMM I get a noticible change in engine rythm but the car runs just as rich - as though it is always in the warm up phase (O2 sensor reads .96 V after a steady rise from .45V at start up). Can I diagnose a bad AMM function?

4. Can the Hall sensor create a bad mixture? Ingine timing is at 12 degrees at idle and egnine seems to idle fine - timing advances smoothly when throttle is increased. Does this indicate a good sensor?


Below is my previous post for some background on what I have done:



I have been trying to figure out a rich running problem for some while. I have an 1985 760 Turbo with 185000 miles. The initial symptoms were the car would run for 5-10 minutes and then choke - I would wait and then start again, go 2 miles and it dies again. After being towed home I spent the next 6 months trying to fix the problem - after many parts, time, and research I have learned a lot about the car but not yet fixed the problem.

Car will start and run fine but O2 sensor reads between 8.9 and 9.3 Volts meaning a rich mixture - will typically choke on gas about 15-20 minutes after running.

Here is what has been in order over a 6 month:

-Throttle Body cleaned
-Fuel pressure regulator has been replaced
-Fuel relay checked – operational
-Injector Ballasts tested for proper resistance - check
-Fuel pumps both working – audible
-All fuses intact
-Air filter clean
-Hall Sensor gauge jumps when cranking - assume operational
-Cap and Rotor replaced
-Coil to Distributor Wire Replaced
-Coil swapped with new coil - no fix
-ECT (Engine Temp Sensor) replaced
-O2 sensor replaced - readings are true - leans when induce air leak
-Engine wire harness - removed - much corrosion, replaced all bad wiring and --installed
-Injectors cleaned and balanced.
-Engine computer swapped - no fix
-No leaks found in piping


Thank you