03 Deville Misfire and Poor Performance
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 03 Deville Misfire and Poor Performance in Past Cadillac Vehicle Discussion; 2003 Deville started occasionally misfiring (hesitation) when driving at constant highway speed every hour or so. Steadily got worse to ...
  1. #1
    BigRedBarn is offline Cadillac Owners Member
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    03 Deville Misfire and Poor Performance

    2003 Deville started occasionally misfiring (hesitation) when driving at constant highway speed every hour or so. Steadily got worse to the point that it has very poor acceleration and misfiring at all times. P0101 Mass Air Flow performance and P0300 have been consistently reported (determined to be Cylinder 1). Had one occurrence of a P0340 Camshaft Position Sensor Circuit and one occurrence of a P1381 Misfire with no communication with Brake Control Module. Recently driven 40 miles (non-highway) with no codes at all though still poor performance.

    I checked MAF connections and wiring routing and cleaned throttle plate with no noticeable impact. Can't seem to find any way to check the MAF Sensor -- should I just replace it? I am really struggling with what could cause a misfire/hesitation in mid steady speed driving.

    Appreciate any thoughts....

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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 03 Deville Misfire and Poor Performance

    With a P0101 code I'd probably go ahead and change the MAF sensor. Give the TB a good cleaning while you're there.

  4. #3
    Mojo88's Avatar
    Mojo88 is offline Cadillac Owners Fanatic
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    Re: 03 Deville Misfire and Poor Performance

    Any possibility of water in gas, or spoiled gas? Any time I have an issue like this, I immediately dump in a couple cans of fuel cleaner (Techron) and maybe some dry gas too. Is the fuel filter old? It might be restricting flow. I would check air filter too, and look around under the hood, with a very bright light, for any vacuum lines that might be broken or fell off. I always start with the very basic stuff, even if codes are being thrown...

    Good luck, Dave

  5. #4
    BigRedBarn is offline Cadillac Owners Member
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    Re: 03 Deville Misfire and Poor Performance

    Thanks, Ranger and Mojo88, I had come to the same conclusion and ordered the MAF from RockAuto before leaving for the week on business. It came today and I'm off to install and I'll go ahead and clean the TP again. BTW I did change out the Air filter previously and the gas filter probably 25,000 back -- good idea to check again. I'll have to try the techron thing -- was always a little cautious about putting stuff in the fluids. Will let y'all know....

  6. #5
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 03 Deville Misfire and Poor Performance

    Quote Originally Posted by BigRedBarn View Post
    I'll have to try the techron thing -- was always a little cautious about putting stuff in the fluids.
    It won't hurt anything, but I doubt it'll help either.

  7. #6
    BigRedBarn is offline Cadillac Owners Member
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    Re: 03 Deville Misfire and Poor Performance

    Well, she is definitely happier with the new MAF but still missing a bit at idle and showing weak acceleration. Haven't been able to run on the highway yet -- that should give an idea on the improvement level. Thanks for your help, Ranger, and Mojo too....

  8. #7
    BigRedBarn is offline Cadillac Owners Member
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    Re: 03 Deville Misfire and Poor Performance

    Replaced gas filter, checked the front plugs (the P0300 misfire determined to be #1 misfire no longer coming up)-- normal light grey residue, all injectors sounding good, no vacuum leaks identifiable. Still runs like a dog -- hills max out at 50 mph -- WOT is a joke with uneven hesitation -- gas mileage down 20%. No codes thrown in the last week. At my wit's end -- any thoughts?

  9. #8
    Mojo88's Avatar
    Mojo88 is offline Cadillac Owners Fanatic
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    Re: 03 Deville Misfire and Poor Performance

    Restricted exhaust? Clogged cat?

    Bad/contaminated gas will also cause symptoms exactly as you describe. I would drain tank thoroughly, and refill with fresh gas from "top tier" station.

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