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360 Wagoneer carb backfire issue...

Discussion in 'Performance & Tuning' started by TheFlynn, Oct 3, 2016.

  1. Oct 3, 2016 at 1:38 PM
    #1
    TheFlynn

    TheFlynn [OP] New Member

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    I've got an '87 Grand Wagoneer that has recently started running really badly. It is hard to start. Idles poorly cold. And, has about 10% power. When in motion, it will backfire out the carb. Quite often, almost always, after a few backfires, it will suddenly run great, as long as throttle is maintained. At a stop or long coast, it will resume the malfunction. Also, I've sprayed carb cleaner into the carb, which temporarily fixes the problem, sometimes. Odd...
     
  2. Oct 3, 2016 at 6:01 PM
    #2
    TheFlynn

    TheFlynn [OP] New Member

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    That doesn't explain why backfiring would make it run normal for a while.
     
  3. Oct 3, 2016 at 6:34 PM
    #3
    chris4x4

    chris4x4 With sufficient thrust, pigs fly just fine Moderator

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    Yeah, I agree with checking the timing.
     
    C2T likes this.
  4. Oct 3, 2016 at 8:54 PM
    #4
    OFFGRID

    OFFGRID Well-Known Member

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    1979 Jeep CJ7, 258, TH350, NP208
    Howell fuel injection, header, HEI distributor, TH350, NP208, SOA lift with YJ springs in the front & GW springs in the Rear. AMC20 with G2 1 piece chromos trussed, Dana 30 with G2 chromos and 760x ujoints and MM Stainless Hubs, Geared 4.56. Tom Woods shafts, Metal cloaks, Caged, 37" Toyo MTs.
    Is it backfireing at idle or when you are taking off. Sounds electrical or malfunction timing advance from the distributor. Check all you plug wires first and make sure none are grounding out on exhaust manifold and the like. If a plug wire is burnt through it will do all of these things. Check the vacuum hoses for leaks and make sure it is good to the distributor.
     
  5. Oct 4, 2016 at 9:23 AM
    #5
    TheFlynn

    TheFlynn [OP] New Member

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    It only backfires under load, at about 3000(?) rpm. It only backfires when it is in this terrible sluggish mode. It sounds choked. But, I have looked and the choke appears open. After a couple backfires, maybe only one, it runs like a champ until it is allowed to idle. Could this be the EGR valve?
     
  6. Oct 4, 2016 at 9:40 AM
    #6
    OFFGRID

    OFFGRID Well-Known Member

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    Houston
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    1979 Jeep CJ7, 258, TH350, NP208
    Howell fuel injection, header, HEI distributor, TH350, NP208, SOA lift with YJ springs in the front & GW springs in the Rear. AMC20 with G2 1 piece chromos trussed, Dana 30 with G2 chromos and 760x ujoints and MM Stainless Hubs, Geared 4.56. Tom Woods shafts, Metal cloaks, Caged, 37" Toyo MTs.
    Do you still have a cat. How many miles on the jeep. Those old cats were only good for like 150000 miles. Poor exhaust flow can choke a motor and cause drastic power loss especially at higher rpm. Fuel air and spark and timing. Check all these.
     
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