Discussion in 'Chevy Trucks' started by 4LOW, Mar 10, 2000.

  1. 4LOW

    4LOW Guest
    Messages: 0

    Hey all, I have an 86 S10 2WD w/2.5<br>4 cylinder $ EFI. It has an erratic<br>idle that's on the high side and it<br>races a lot. When I give it a quick<br>stomp it'll drop down to a lower rpm<br>that is still a little too high. I suspected<br>a vacuum leak but can't find one. Thanks<br>for any help.<br>4LOW
  2. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    After you have checked all the vac lines,spray some carb cleaner under the TBI unit.If it races more,the gasket is likely blown out.It is cheap and easy to change,they go a lot.If that doesnt do it,pull out the IAC motor,the one with 4 wires on a square connector,and a big 1 1/4&quot; hex head.Clean carbon out of motor and seat inside of TBI unit,reinstall.The IAC may be bad,but you wont know without a scanner.Take it to a mechanic if all those fail to fix it.<p>----------<br>John D<br>
  3. yortengel

    yortengel Senior Member
    Messages: 123

    If you cant find a Vacuum leak, you can check the operation of the IAC motor, you need to turn the ignition on, engine off. (KOEO) jumper the A to B on the ALDL (this is the connector under the steering column) then with the air cleaner off watch the pintle of the IAC motor move in and out of its bore in the Throttle Body. if it moves the the circuit is ok. If its not moving then I recommend that you check out A manual from the library, It should have a complete procedure on how to check minimun idle speed and IAC operation. I you start getting in over your head the take it to the dealer.<br>Good Luck.<br><p>----------<br>Troy L Engel<br>
  4. OP

    4LOW Guest
    Messages: 0

    thanks guys, you were right. i changed<br>the iac & tbi gasket, the intake was<br>choked up with lots of carbon, it was<br>an easy fix.<br>4LOW