Sevice engine soon, rough idle
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Sevice engine soon, rough idle in Past Cadillac Vehicle Discussion; Good Evening, I have a new issue most certainly self induced, after replacing the water pump and re-assembling ALMOST everything, ...
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    Goldencletus is offline Cadillac Owners Fanatic
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    Sevice engine soon, rough idle

    Good Evening, I have a new issue most certainly self induced, after replacing the water pump and re-assembling ALMOST everything, I neglected to reattach the electronic device that clips into the air filter box. The car wouldn't start at all but did have some backfire sounding issues! Not sure at the time what the problem was, I tried, unsuccessfully to start the car, again no success. I went back to the engine compartment and found the problem. Re-connected the culprit and it started right up. that being said, the "Service Engine Soon" light came on. Thinking it would go out after a reboot, I drove the car for about 12 miles to make sure there were no leaks or any other issues from my water pump install project. No problems whatsoever, no leaks, car was running fine (the service light was still on however). After parking for a couple of celebratory beers, I began the 12 mile journey home, at which time the "Service Engine Soon" light began to flash! When I stopped at the next traffic light, the car was running rough as hell. Leaving the traffic light, it ran fine and the service light stopped flashing. Again, when I got home, the rough idling issue was still present and the flashing service light had reappeared. I've not pulled any codes as it's late and dark but thought perhaps someone has had this same experience and can share some insight. Thanks again for all of the help and input!

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    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    The flashing CEL indicates a misfire. That's your rough idle. We'll need the codes and definitions.

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Sevice engine soon, rough idle

    1998 Deville - misfire - How long has it been since a complete spark plug/plug wire change ? A thorough coil and ICM cleaning ? The ICM ground wire.

    AC Delco (DENSO) #41-950 Double Platinum plugs, AC Delco wireset - the $110 one.

    Either www.rockauto.com or talk to Chris in Parts at Rippy Cadillac over there >>>

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Sevice engine soon, rough idle

    Quote Originally Posted by Goldencletus View Post
    I neglected to reattach the electronic device that clips into the air filter box.
    That would have been the IAT sensor, but I didn't think it would prevent the car from starting.

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    rodnok01's Avatar
    rodnok01 is online now Cadillac Owners Connoisseur
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    Re: Sevice engine soon, rough idle

    Quote Originally Posted by Ranger View Post
    That would have been the IAT sensor, but I didn't think it would prevent the car from starting.
    I don't believe it would either as I have left mine of many a time...

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    Goldencletus is offline Cadillac Owners Fanatic
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    Re: Sevice engine soon, rough idle

    Thanks guys, the plugs and wires are new as of one month ago, I haven't cleaned the ICM or coil but will do when I'm back in town, Also I'll get the code with def's on Wednesday. The car was running fine prior to my pulling parts off to change the pump, I guess coincidences can happen, just seems strange.

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    Goldencletus is offline Cadillac Owners Fanatic
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    Re: Sevice engine soon, rough idle

    Good afternoon men, mystery solved RE rough idle, after getting home this afternoon, I had decided the throttle body had to be the issue. I put a full clean on it, reassembled everything, started the car, and was rewarded with a car that barely ran at all. Frustrated and very bothered by the whole coincidence thing, I went back through everything that I taken apart during the water pump replacement. Right next to the trans fluid filler/dipstick was the culprit, a fairly large conglomeration of wires (inside of corrugated plastic conduit) with a sizeable wire connector that I had disconnected to get as much crap out of the way as I could. Bottom line is this was a self induced issue as I didn't get a positive connection when I put the two back together! Car is running great again, thanks for all of the help!

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    Ranger's Avatar
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    Re: Sevice engine soon, rough idle

    OUCH! Nothing hurts worse than a self inflicted wound.
    Thanks for the feedback.

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