[MC968CS]

Hi I have a mystery electrical issue, and would appreciate some guidance or ideas.



The symptoms are

- the car has just started to stall occasionally, such as when idling at lights, or typically just as I go to take off

- it can also cut out under power, such as accelerating away from lights , at 3,000rpm today

- the tacho is now ‘spiking’ occasionally. It just surges from idle or low revs when cruising and spins to 7k+ for a split second, but the engine is not actually revving up. I actually think there is a fraction of a second misfire at the same time



So far I have

- replaced the DME with the new 993… part numbered item, no change

- swapped chips (RSBarn, and ProMax), no change



So, any ideas as to what it could be are appreciated!



Thank you



MC968CS

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[banditsc]

Have you replaced the sensor on the flywheel?

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[MC968CS]

No. I assume in asking, you think that may be a good idea. Have you had some experience with this being an issue?

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[banditsc]

That's where the tach signal is coming from. If that dies no tach signal and no start...

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[MC968CS]

Thanks, that seems pretty logical! Will look into it.



Any other ideas appreciated too. Thank you.

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[banditsc]

I had a recent almost stall issue at low RPM when taking off at lights that was a failing HALL sender, but the tach didn't go erratic when it was happening. So I'd start with the flywheel sensor first since the tach signal comes from there. It's a common failure point.



There is a cheaper BMW part number for that sensor, same sensor but longer wire. Bosch [color="#0170a7"]0261210002[/color]

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[MC968CS]

Thank you. Just checking, is that alternate BMW part for the flywheel or HALL component?



MC968CS

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[banditsc]

It's for the flywheel. I haven't found an alternate for the hall that is cheaper.

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[MC968CS]

Banditsc, thanks for the input. Sure enough, is all fixed with a new flywheel sensor.

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[banditsc]

Great...

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