Tomorrow I am replacing the stage module I recently purchased with another unit as my Tach is fluctuating and the car is not giving a steady idle. It is also hesitating a bit. The car mechanic diagnosed the wiring and all the things lead to the stage module has anyone had this problem before??. I hope that it is a defective module and not the ECU "ouch"
Spurt Montreal.
Thanks to any one who has a point of view on this problem.

Although I didn't have the idle problem, I did have the
jumpy tach just before mine died completely. Turned out
to be a dead short in the tach/tach harness itself.

Andy

In your previous reply to me you stated: "I believe that I have a new Hall Sensor as the Swedish out mechanic put in a new cap and rotor."

A new cap and rotor would not include the hall sensor, which is riveted to the base of the dist. and is often replaced by changing the complete distributor, which I think you'd know about (expensive for a new one).

It would still make sense to check the hall as this fires the ignition pulses initially. One check is to listen for the fuel pump just after cranking (assuming no start condition). If the pump runs for a second, the hall is OK, otherwise suspect it because the pulse train from the hall is needed for the ECU to power the fuel pump relay. If pump runs, then both hall and ECU are OK pointing to the power stage as the culprit.

BTW, if not done already, carefully check the connection and wiring to the hall sensor - a known source of trouble as the vibration leads to intermittent failure. Regards.
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BillB

Good evening Bill,
I thought about what you said. Today I changed the power stage for another cause I thought that by chance it was defective and it was not at fault. I went back to the mechanic where I had the original work done and they had not done what I asked and put in a new Hall sensor. So now they are putting a whole new unit in 2 morro. It will cost but I am at the end of my budget on this project for now so I believe that this should resolve the problem. There is still a backfire problem so 2morro morning I will again instruct them to change the flame trap. I did have my doubts so I went back today cause she was idling horribly.I am not going to use them again, at least I will not have to pay for the labor this time. I thought that the new timing belt was messed up from when I made that fuel injection cleaner error. Thanks for the good advice Bill and cheers to you.
Spurt Montreal
Myles Clarke
1988 Volvo 740 GLE 213,000 km
Manual 5 speed non turbo

The backfiring can be caused by a defective hall sensor - happened to me. Just before it finally failed there was a loud backfire. I think the new hall will solve your problems. Regards.
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BillB