Strange LT1 Tach problem- works until 4200rpm, then goes to zero
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Strange LT1 Tach problem- works until 4200rpm, then goes to zero
I have a 1995 LT1 swapped into my T/A. I've tried two 3rd gen tachs now, with the same result. I've used a 8000 RPM tach from an L98 car that I know for certain worked perfectly with the original L98, and I've also used a 6000RPM tach from a 305 TBI car. For both, I will slowly accellerate and the tach will move up smoothly until 4200 RPM, then it drops off the table to zero and stays there until I drop below 4200 RPM again. The engine doesn't get choppy or anything when this happens, it appears to just be the tach that acts funny. Does anyone know what is causing this?
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__________________ Bright Platinum Metallic exterior with painted hoodbird. Black interior with 2002 Trans Am Ebony leather seats. Smoothed inner fenders.
Current Drivetrain: LT1 and T56 with SLP 1 3/4" primary headers and catback: 8.85 seconds in 1/8 mile w/ lousy street tires.
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Re: Strange LT1 Tach problem- works until 4200rpm, then goes to zero
Do you have it hooked to the tach output from the PCM? Mine did the same thing. I ran the white tach wire directly from the C100 connector to the coil and it fixed my problem.
Re: Strange LT1 Tach problem- works until 4200rpm, then goes to zero
Quote:
Originally Posted by bingo
Do you have it hooked to the tach output from the PCM? Mine did the same thing. I ran the white tach wire directly from the C100 connector to the coil and it fixed my problem.
yeah, i do have it running from the pcm. I'll have to try what you did. Thanks!
