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wheres the tach. wire on a 87 chevy 5.7 ?

Discussion in 'Chevy Trucks' started by mushplows87, Dec 23, 2008.

  1. mushplows87

    mushplows87 Junior Member
    Messages: 11

    hello, i am trying to set the idle on my 87 silverado 5.7 throttle body engine...i actually got the information on how to do that here...but as simple as it probably is i cant find what wire to probe to get the r-p-m .....thanks alot Joe

    JRKRACE Senior Member
    Messages: 172

    Pretty sure you can pick it up off the HEI distributor. IIRC, there a little box molded into the side of the distributor that has 2 contacts underneath. 1 of them is a tach pickup.

    Don't fault me because the last time I put a tach in was 20 years ago....
  3. M Runner

    M Runner Junior Member
    from NW Ohio
    Messages: 21

    If it is an HEI ignition (the ignition coil is in the distributer cap) then yes there is a terminal for the tach, it should be labeled (-) on the plastic cover on top of the cap.
    I think though your engine may have an external coil. If that is the case you will need to tap into the negative wire coming off the coil. They make a plug with a pig tail on it that taps right into the coil that you plug your OE harness into.
  4. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Your TBI truck will be HEI of course, but its the small cap HEI with the external coil.

    If you look on the coil connections you'll see a pink wire, and a white wire. The white wire should have two leads coming off the coil. One will be about 3 inches long and have a plastic Packard connector on the end hanging loose, or taped to the other wires. That one is your aux tach lead.
  5. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    how were you told to set base idel on a tbi engine.?

    there is a 4-5 step way to do it. but you should never have to play with it.

    have you checked for a vac leak or bad iac valve?

    more of the story will help first.
  6. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    :waving: Right here sweet. All explained
  7. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    just making sure. seen lots of people post up on other sites and thay have it all screwed up.
  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Same here sweet. Too many times you'll see guys do nothing but pop the anti tamper plug out of the TB and start cranking on the idle speed screw...and then can't figure out why it didn't work as intended.