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Carbed 2.8 miss with low compression

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  • Carbed 2.8 miss with low compression

    Okay folks, I have one for you. My '85 Jeep Cherokee with the GM 2.8 V6 is acting up. Here's what's going on:

    it has had a pretty bad miss at idle in one cylinder. I narrowed it down to #1 by pulling each plug wire one at a time until pulling #1 made no difference. With that said, it doesn't ALWAYS have this miss at idle. New plugs/wires/cap and rotor made no difference.

    Comoression test:
    1. 125 (130 with oil)
    2. 165
    3. 185
    4. 185
    5. 185
    6. 180
    Notice the #1 cylinder only gained 5psi with oil? Seems odd to me. That doesn't sound like a ring problem.

    There is no horrible blow by, no backfiring, no coolant loss, and it seems to run okay once it's off idle, and driving. There DOES seem to be spark knock/detonation/pinging and to me it sounds like there's only one cylinder doing it. This tells me lean mixture in that particular cylinder. But if it had a bad valve, wouldn't it backfire?

    I wont say I'm at my wits end, but I'm getting close. Has anyone ever experienced this?

  • #2
    Turned out to be a burnt exhaust valve.