Does my 1988 740 turbo have either an ignition system control unit (different from the LH control unit) and/or a charge air overpressure switch. In the Volvo green book both are included as components of the LH 2 Jetronic system and are pictured as being located above the gas pedal. Does my car have either of these and what do they do? Could either cause the ignition to shut off instantly. Intermittently, the engine just quits....instant shut down. The usual suspects have been replaced including fuel pump relay, radio suppression relay, and air mass meter. Thanks for all suggestions/info.

Is there any oil in the tube going to the charge pressure switch under steering wheel or it getting to any electrial coponents?This always seems to be a worry.On the left fender amodule will act up like that until it stops all together.Hall sender with oil in it gets a little touchy also.

Your car has both items. The charge overpressure switch shuts off the fuel pump if boost pressure gets too high. The EZK unit determines the spark advance and controls the Power Stage. The Power Stage is the ignition amplifier and controls coil current. It is located above the battery on the inside of the left fender well in your turbo car. The Power Stage could be your problem.

I would suspect the Hall effect sensor, or the wires to it. Does the tach drop to zero when the engine stalls? If so, you have a problem with the low voltage side of the ignition system. Sometimes the Hall effect connector breaks out of the distributor and hangs by it's wires. That is great for an intermittent stop. Ask me how I know!

I just installed a new power stage. Quick, easy and $85. However, since the car was running again when I did it, I have no way of knowing if I actually fixed anything. The Hall effect sensor is between 6 & 7 years old, connections look good. Is there a way to test the hall effect sensor and/or EZK to verify they are working properly. If I could do that, I would then conclude that the power stage was probably the culprit. Again, all suggestions cheerfully accepted.