New Twist on the Stalling/Missing Prob

[ZOA NOM]

I just finished Hell Week, complete with missed days of work, and plenty of cussing and spitting. I started out the usual way - looking through this board for similar issues, etc. I went after the usual suspects; Cleaned ICV, replaced O2 and Head Temp Sensors, cleaned Air Flow Volume Sensor and Vane, cleaned and inspected DME circuit boards, swapped and checked DME relay, all to no avail. What saved my bacon, was that my wrench allowed me to borrow an inline tester to check each output from the DME while the car was running. Many of the voltage checks that I found were a couple of volts high, which led me to check the Voltage Regulator, and "voila" she was putting out nearly 16 volts. Initially, this didn't register as a problem because you usually expect presence or absence of voltage, and don't necessarily pay attention to overvoltage as a problem.

For those who wander down this path in the future, the easiest check to indicate the voltage regulator as a problem is the presence of more than 6 volts at the connector to the Air Flow Sensor. There are four pins in the connector, and the third pin from the left as you look into the connector should have no more than about 5 volts from the DME. This high voltage, along with the nearly 16 volts supplied as the main voltage to the DME seems to have confused it.

[stlrj]

Where you able to get by with a new regulator or did you replace the entire alternator assembly?

I seem to be having similar problems and am wondering what to expect to pay for the parts if I do it myself or have it done.

Cheers,

Joe

[ChrisBennet]

Excellent info Zoanas.

According to my notes, I think that pin (pin 9 DME, pin 3 at connector) should have exactly 5 volts. It's the reference voltage for the air flow meter. I'm surprised it would go over 5 volts.
-Chris

[ZOA NOM]

Joe, the regulator is a separate, removeable part. Cost was $75 through my wrench. Pretty easy removal and install. I even managed without a two-pronged fan pulley wrench!

Chris, no kidding, it seems like the whole Motronic system is a finicky beast. I consistently measured 6 volts or greater throughout my troubles. I am actually very satisfied with the whole experience this week, because I really got a chance to get to know the car better, and became much more confident in working on it. Thank God for my wrench, who gave me full access to his mind and tools for nothing more than the cost of parts. I can't imagine how much I could have spent. My total for the week was about $550 which included everything that was probably due for replacement anyway. Rotor and cap, O2 Sensor, Head Temp Sensor, Fuel Filter, Regulator, Bentley Manual, and an air filter.

I'm on cloud nine.

[ChrisBennet]

Originally posted by ZOANAS

Chris, no kidding, it seems like the whole Motronic system is a finicky beast. I consistently measured 6 volts or greater throughout my troubles.

OK, I just measured pin 9 on my bench and it was 5.02v. Then I powered it down and powered it up and then it read 5.99v. I traced the circuit with my voltmeter to see where it was and somewhere during that, it went to 5.99v (WTF?). Sooo, my notes are wrong, it isn't regulated at 5v. Thanks for cluing me in.
-Chris