1984 deville running rich blowing out black smoke
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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, 1984 deville running rich blowing out black smoke in Past Cadillac Vehicle Discussion; Ive been having this problem for a loong time and still havent found the problem. the car exhaust is throwing ...
  1. #1
    dmuny is offline Cadillac Owners Member
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    1984 deville running rich blowing out black smoke

    Ive been having this problem for a loong time and still havent found the problem. the car exhaust is throwing gas out i took it to my local mechanic he told me i need a new ecu. he tried a remanufactured one from o reily but it was worse the car couldnt even function. I have tried everything new plugs wire distributor coil timing map sensor coolant sensor fuel injectors rebuilt the fuel injector housing and fuel regulator.... My mechanic says its the ecu but i need to get one off a good running cadillac? I dont really want to gamble on paying for an ecu and it b faulty but if this is what its going to take. Sometimes the car will get a good reading i guess and run good but all of a sudden switch up and start dumping black smoke everywhere... This is my third mechanic i go too and has got the closest to fixin it everybody else has no clue i would hate to get rid of the car since its been my project car for quite some time. Im bout to b 21 in june so i wanna have it ready and this is about the only problem i have ever had on it besides basic stuff like brakes alternator...i was told by another wise man that it has an air temp sensor that could b the problem... Please help me fellow cadillac mates...

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  3. #2
    SafariOne is offline Cadillac Owners Fanatic
    Automobile(s): 1981Cadillac Fleetwood Brougham D'Elegance Coupe m
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    Re: 1984 deville running rich blowing out black smoke

    It could very well be the ECM as I had the same issue with my 81. It is not the whole ECM just the prom chip but they are hard to come by on their own. If you can find an ECM at a wreckers just switch out the proms and see what happens. It will cost between $200-300 to have your own rebuilt. The air temp sensor would not cause such a rich mixture. The MAP sensor could be part of the problem.

  4. #3
    dmuny is offline Cadillac Owners Member
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    Re: 1984 deville running rich blowing out black smoke

    Prom chip? Would that require opening up the ecu?

  5. #4
    csbuckn is offline Cadillac Owners Master
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    Got a factory remaned one for you off my 84 with 4.1L, $40 shipped.


  6. #5
    jayoldschool's Avatar
    jayoldschool is offline GM RWD V8 addict
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    Re: 1984 deville running rich blowing out black smoke

    What codes does it show? Start there.

  7. #6
    SafariOne is offline Cadillac Owners Fanatic
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    Re: 1984 deville running rich blowing out black smoke

    Yes ....you will see a small access panel on the top with one screw holding it on. You go in there and unplug the prom and very carefully plug in another one. They have many small delicate pins that have to line up on the motherboard socket and then gently push it all the way in. The prom is the larger one and the calpac is a litttle bit smaller right next to the prom.

  8. #7
    dmuny is offline Cadillac Owners Member
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    Re: 1984 deville running rich blowing out black smoke

    Csbuckn i pm'd u....

    Jayoldschool i tried toget codes off the temperature control but it doesnt work good at all can barely read it.....

    Safari one sounds a lil complicated i wouldnt want to take it off and mess it up

  9. #8
    acerulz1 is offline Cadillac Owners Member
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    Re: 1984 deville running rich blowing out black smoke

    had the same thing with mine, found a small crack in the rubber hose at the throttle body that supplies vacuum to the map sensor. looked like a diesel running rich lol.

  10. #9
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: 1984 deville running rich blowing out black smoke

    I thought it sounds like a MAP sensor but you should just check for codes first.

  11. #10
    dmuny is offline Cadillac Owners Member
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    Re: 1984 deville running rich blowing out black smoke

    I can't check the codes my climate control doesn't fully show the numbers -_- I replaced the map sensor no difference

  12. #11
    dmuny is offline Cadillac Owners Member
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    Re: 1984 deville running rich blowing out black smoke

    imma try the ecu csbuckn is offering and then ill go from there

  13. #12
    dmuny is offline Cadillac Owners Member
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    Re: 1984 deville running rich blowing out black smoke

    Ok so after installing the ecu from csbuckn and new fuel pump wires spark plugs rhe running rich problem has gone away although every once in a while on start up it will blow a lil black smoke and go away? And aldo my ac is now only blowing when i step on the gas it blows cold and the vent seems to b stuck shooting to the bottom

    Any help is greately appreciated

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