1994 Deville Running Rough
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HT4100 4.1, 4.5, 4.9 Discussion, 1994 Deville Running Rough in Cadillac Engine Technical Discussion; Alright guys, heres my problem. This condition comes and goes, sometimes goes away for days at a time, other times ...
  1. #1
    Laker_Dynasty is offline Cadillac Owners Member
    Join Date
    Jul 2004
    Posts
    97

    1994 Deville Running Rough

    Alright guys, heres my problem. This condition comes and goes, sometimes goes away for days at a time, other times it acts up every time I drive it. There seems to be no rhyme or reason as to why or when it does it, but at times, the car will backfire and hesitate at various speeds, sometimes so bad the car just won't move. To remedy the immediate problem, I can pull over, turn the ignition off, and restart the car, then it will run fine again for a few minutes or even hours. I ran the codes and came up with this
    PO52
    IO39
    IO52
    No ACP
    No SIR
    I did a search on these codes, but they really don't tell me anything. Just FYI also, the cars catalytic converter has been removed, but I have a new one to put back on it, just haven't had the time to have it done, not sure if that could be causing the problem or not. Anyways, thanks in advance.

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  3. #2
    boston94deville is offline Cadillac Owners Member
    Automobile(s): 1994 Deville
    Join Date
    Mar 2009
    Posts
    24

    Re: 1994 Deville Running Rough

    I'm having the exact same problem. Any luck?

  4. #3
    daniel58 is offline Cadillac Owners Fanatic
    Automobile(s): 58 Coupe Deville, 77 Coupe deville, 90 Deville
    Join Date
    Sep 2009
    Posts
    183

    Re: 1994 Deville Running Rough

    Check fuel pressure (with a gauge) when it is acting up, it could be the fuel pump or the pickup in the tank. Also it would'nt hurt to check every vacuum line you can get to and make sure every thing is plugged in etc.

  5. #4
    boston94deville is offline Cadillac Owners Member
    Automobile(s): 1994 Deville
    Join Date
    Mar 2009
    Posts
    24

    Re: 1994 Deville Running Rough

    Quote Originally Posted by Laker_Dynasty View Post
    Alright guys, heres my problem. This condition comes and goes, sometimes goes away for days at a time, other times it acts up every time I drive it. There seems to be no rhyme or reason as to why or when it does it, but at times, the car will backfire and hesitate at various speeds, sometimes so bad the car just won't move. To remedy the immediate problem, I can pull over, turn the ignition off, and restart the car, then it will run fine again for a few minutes or even hours. I ran the codes and came up with this
    PO52
    IO39
    IO52
    No ACP
    No SIR
    I did a search on these codes, but they really don't tell me anything. Just FYI also, the cars catalytic converter has been removed, but I have a new one to put back on it, just haven't had the time to have it done, not sure if that could be causing the problem or not. Anyways, thanks in advance.
    Check the battery cable for corrosion. I had the exact same madness with my caddy and it worked. BTW, be prepared to be laughed at when you talk to your mechanic about it, and be aware that the price for an OEM cable is ~$200

  6. #5
    frostycadillac is offline Cadillac Owners Member
    Automobile(s): 1968 DeVille, 1985 Seville, 1990 Deville, 1994 Deville,
    Join Date
    Oct 2009
    Location
    Tampa, Florida
    Age
    53
    Posts
    43

    Re: 1994 Deville Running Rough

    These car inherit of bad injectors. Run the computer test to see which injectors are not changing the RPM, you may be surprised. If you need the instructions to do so from the climate control system, let me know, I can walk you through each step. There are threads in here under fuel injectors that will tell you the steps too. A set of clean injectors will make your car run like it just left the showroom.

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