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Thread: Backfiring issues

  1. #1
    rachmadd is offline Cadillac Owners Member
    Automobile(s): 1999 cadillac deville
    Join Date
    Jan 2012

    Backfiring issues

    Well let me first say that I need a new radiator cap because it is not holding pressure. So I was stuck in the snow and in the process of trying to get unstuck I smelled coolant which I attributed to the radiator cap releasing steam. Then my light came on telling me to idle transaxle because it was hot. So I shut it off and let it sit for a while. Then as I was trying to get unstuck my car began to backfire with a horrible smell. and now idles rough. What could this mean? The car is a 1999 Cadillac Deville 8 cylinder 4.6 liter.Please help!!!

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  3. #2
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
    Automobile(s): 2002.5 F55 STS - 67,500 miles, 2014 Explorer XLT FWD
    Join Date
    Feb 2006
    MD Eastern Shore, Kent Island

    Re: Backfiring issues

    Pull your diagnostic trouble codes from the car's built-in code scanner/memory. Use the sticky post ^^^ "How to pull codes". Study for which DIC readout control procedure you need to use.

  4. #3
    vincentm's Avatar
    vincentm is offline Cadillac Owners Connoisseur
    Automobile(s): 1997 Cadillac Eldorado ETC
    Join Date
    Aug 2010
    Kennewick WA

    Re: Backfiring issues

    And post the definitions!

  5. #4
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Woodstock Ill.

    Re: Backfiring issues

    I would diagnose the engine and trans overheating problem before worrying about anything else.

    How do you know that the cap is bad and not holding pressure?

  6. #5
    johnny kannapo's Avatar
    johnny kannapo is offline Cadillac Owners Connoisseur
    Automobile(s): 1996 Eldorado
    Join Date
    Oct 2009
    Pigseye, Mn

    Re: Backfiring issues

    You can get the codes right off the dash board DIC without tools, write them down. There is a procedure using the heater control buttons.
    Go to- "Reading OBDII codes" at this link-
    Then navigate that site & find the list of codes & definitions & post them back here for more help.

    I hope you laid off when the warning messages lit might be ok.
    At some point the engine should have gone into limp mode and that may cause the poor running condition.

    You now know this is about as destructive a thing you can do to a transmission. That alone is a possible $3000 repair.
    If you over heated the transmission it's a cinch to figure the engine over heated and the radiator cap is not likely the reason.

    It's possible the radiator fans are inoperative.

    I hate to say it but it sounds like you tortured the engine & transmission in a barbaric fashion and something major in the engine may have given out.
    I could be wrong, I wasn't there.
    Last edited by johnny kannapo; 01-21-12 at 04:31 AM.

  7. #6
    maeng9981's Avatar
    maeng9981 is offline Cadillac Owners Connoisseur
    Automobile(s): 14 SRX, 00 SLS, 99 Deville 50-year Anniversary
    Join Date
    Mar 2009
    Dallas, TX

    Re: Backfiring issues

    Sounds like the engine overheated and it went to camel mode - you might find P1258 history. Were you just mashing the throttle to get it unstuck?

  8. #7
    Mark D is offline Cadillac Owners Member
    Automobile(s): 1995 Seville STS 1998 Seville STS 1995 Seville SLS 2000 ET
    Join Date
    Nov 2011

    Re: Backfiring issues

    Stuck in the snow, eh? Well, your air intake is just behind the left headlight and takes it air from down low. That crappy running could also be snow ingested into the system. I have a friend who's daughter was driving his STS and drove through deep water. Engine ingested water enough to destroy it. Water doesn't compress. He had to get a new engine. Snow wouldn't be quite so bad, but sure can raise hell with drivability.
    Mark D.


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