HT4100 Backfires
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HT4100 4.1, 4.5, 4.9 Discussion, HT4100 Backfires in Cadillac Engine Technical Discussion; Just repalced all the belts on my 1985 FWB what a mission Now she has been stuttering a little and ...
  1. #1
    305Caddy's Avatar
    305Caddy is offline Cadillac Owners Member
    Automobile(s): 1985 Fleetwood Brogham RWD
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    Exclamation HT4100 Backfires

    Just repalced all the belts on my 1985 FWB what a mission
    Now she has been stuttering a little and some times she even back fires the only thing I did differant was correctly install a belt that goes from the crank pulley to the air/smog pump pulley and fan pulley.


    When I bought her she had a belt that bypassed the air/smog pump pulley and only wrapped around the fan and crank pulleys (dont ask me how the previose owner did that one). Besides a leaky power stearring pump and an odometer that has flipped twice over the engine ran great. now comes the stutter and ocasional back fire

    Any one have any ideas why this is happening?

    here is a stock picture of A HT4100 and how the belts should be routed

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  3. #2
    z06bigbird is offline Cadillac Owners Connoisseur
    Automobile(s): Sedan de Ville, CTS
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    Re: HT4100 Backfires

    Prev owner knew he had bad smog pump. Used to be big $$.

  4. #3
    CaddyshackCadillac's Avatar
    CaddyshackCadillac is offline Cadillac Owners Fanatic
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    Re: HT4100 Backfires

    i would check your spark plugs and wires i had an 85 monte that had burned thru one of the wires and backfired like crazy.....

  5. #4
    Jonas McFeely's Avatar
    Jonas McFeely is offline Cadillac Owners Connoisseur
    Automobile(s): 1996 DeVille, 1985 Brougham SAGE GREEN!
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    Re: HT4100 Backfires

    See sig.

    I honestly dont know. Mad respect for the HT4100.

    Captain Morgan.

    Im looking at boobs now. omg. Life is good.

  6. #5
    noahsdad's Avatar
    noahsdad is offline Cadillac Owners Connoisseur
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    Re: HT4100 Backfires

    Try disconnecting the A.I.R. pump and seeing if it runs better. It could be either the pump itself or more likely the valve that diverts air to the cat, air cleaner, or atmosphere.

  7. #6
    305Caddy's Avatar
    305Caddy is offline Cadillac Owners Member
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    Re: HT4100 Backfires

    I dont care what they say about you Jonas, your the man
    I disconected the hoses that led to the filter pan and so far so good now for some smilie war


  8. #7
    305Caddy's Avatar
    305Caddy is offline Cadillac Owners Member
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    Re: HT4100 Backfires

    she is still backfiring, but I have bigger problems! Some wanna be thug backed his uncle's Dodge Ram in to my driverside front fender and then tryed to whip. Im gonna post the story up.

  9. #8
    CaddyshackCadillac's Avatar
    CaddyshackCadillac is offline Cadillac Owners Fanatic
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    Re: HT4100 Backfires

    did you ketch em?

  10. #9
    Melrose is offline Cadillac Owners Fanatic
    Automobile(s): 1999 Deville, 1987 Eldorado
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    Re: HT4100 Backfires

    Went through the same problem on two 4.9's. After much time and money the problem was a worn distributor gear. Have your mechanic put it on a scope and the inconsistent firing will show up. The on-board diagnostic codes showed nothing.

  11. #10
    carnut is offline Cadillac Owners Master
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    Re: HT4100 Backfires

    Thats why they call them "RAMS"

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