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Bad gas mileage

Discussion in 'Wrangler YJ (1986-1995)' started by Hray, Oct 15, 2021.

  1. Oct 15, 2021 at 3:21 PM

    Hray [OP] New Member

    Oct 15, 2021
    Blue 1989 Wrangler
    Hi new to this forum have a problem with my 89 Wrangler. It idles like there is no problem but if I hold my hand over the throttle body it continues to run with no change of the motor idle speed. It hesitates a little in acceleration also. I have checked and rechecked and can't find a vacuum leak which is what I suspected it to be it's a 2.5l if anyone has any experience with issue it would be greatly appreciated thanks for any advice
  2. Oct 15, 2021 at 5:04 PM

    Groundfault Well-Known Member

    Jul 4, 2021
    First Name:
    87 Wrangler, kind of...
    5.7 V8 with Whipple Supercharger, TH350 w/B&M Shifter, NP205 TC, Dana 60 front 4.56, GM 14 bolt 10.5 rear 4.56, 4 wheel discs, Bilstein shocks, 6" lift on 37's, Autometer gauges, all led lighting and a few other things.
    Is the idle rpm normal? If yes, it's probably not a vacuum leak or IAC.
    How many miles on the spark plugs, plug wires and fuel filter? Low fuel pressure or poor spark will cause both bad fuel mileage and hesitation under acceleration.
    No loss of power, just hesitation during acceleration probably eliminates a plugged up cat, but doesn't totally eliminate the O2 sensor even if it hasn't set the CEL yet.
    Most of the problems with a YJ can be directly related to square headlights:)
    Always glad to see another square still on the road. Post some pictures when you can.
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