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Old 10-03-2017, 11:04 AM   #1
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satsrbz is on a distinguished road
Join Date: Dec 2012
Posts: 15
Default Tach (not engine) goes to 8000 rpm.Back to zero on restart

1999 SL2. 50,000 miles.

Driving the other day, everything fine then tach started going higher and higher, ending beyond 8000 rpm.
No service lights. Car ran fine.
Tach stayed beyond 8000 when I shut engine off.

After I finished errand, I restarted car and tach moved back to 0 and went to correct rpm over about 5 second period.
Video attached of return to zero on start-up. I guess not. Can't upload video.

It is intermittent. Sometimes days go by with no problem.
If I try to restart shortly after it goes to 8000, it doesn't reset to zero.
It needs to sit for some period of time and haven't figured what the threshold is for that yet.

Was able to watch it climb last night. As I accelerated the tach would go up, but not down, as rpm changed and transmission shifted. It would go up a few hundred rpm on upshift or downshift, or change in rpm, until it maxed out over 8000. Again, the engine ran normally, no over revving.

I don't know if this is a precursor to something, if it can be fixed, or just a glitch to live with.



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