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Thread: tach loss and bucking under boost/ hall effect ring help

  1. #1
    Join Date
    Sep 2011
    thornton, co

    tach loss and bucking under boost/ hall effect ring help

    since i had a new to me used motor with about 70k on it put in my sc, i have had issues with tachometer loss intermittently. when this happens the car misfires from time to time and shuts off under boost after bucking for a moment.

    i have switched cam sensors, wiring harnesses and DIS modules still had the same issues. I was reading in the forums about crank sensor could be the cause as my shift lite is on during starting process/key on. so i replaced it as well as my balancer/damper and installed underdrive pulleys. I after machining down the spacer for proper alignment of the alternator thought we were in business. but no such luck. When i replaced balancer i also bought a hall effect ring from another member as my old one was thin from the balancer about ready to disintegrate. when i put it on the new BHJ balancer there was a 5th hole on the ring, i thought this to be an alignment hole, but being the guy i am didnt thing to look at the old one before disassembling it. i lined the 5th hole of the ring up with the dimple so to speak on the BHJ balancer. the car started at first but there was no tach for a brief moment then it was on, then back off. is it possible the sensor is faulty? or is my assumption that i put the ring on wrong more so the probable issue?

    Thank you in advance for your help
    if anyone could post pictures of the early model ring and balancer that would be greatly appreciated.

  2. #2
    Join Date
    Jun 2015
    Palos Heights, IL (Chicago suburb)

    similar problem

    I had a similar problem about a year & a half ago. I was occasionally seeing the tach drop to zero accompanied by hard bucking/shaking, which I could tell was definitely engine related, not transmission or rear-end. After doing some diagnostic work myself, I took it to my mechanic with the suggestion they look at the cam sensor. They agreed that was the problem, swapped it out & problem solved.

    In your case, I'm wondering if the balancer alignment isn't correct, as you suggest, because replacing the cam sensor should have solved your tach issue.

  3. #3
    Join Date
    Jul 2005

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