03 Deville hard idle and bogging out lower speeds
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Northstar Engines and System Technical Discussion Discussion, 03 Deville hard idle and bogging out lower speeds in Cadillac Engine Technical Discussion; Hi, I just bought an 2003 deville a couple of months ago. Everything worked great, no check engine light, idled ...
  1. #1
    arduino is offline Cadillac Owners Member
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    03 Deville hard idle and bogging out lower speeds

    Hi,

    I just bought an 2003 deville a couple of months ago. Everything worked great, no check engine light, idled fine, rode fine. I have changed the oil once. Just a couple of weeks ago the "service engine soon light" started coming off and on. It would start up with it off (no ruff idle at this point) and would turn on after about 30 min freeway driving. Now it stays on constantly and idles very ruff. Also when it first started I did not notice any power loss or bogging. Under the hood I can hear a strange sucking, whisping noise which decreases when I open the throttle, but it's getting worse the longer I am going. I've changed the plugs, air filter, fuel filter, and checked all the coils which are practically brand new and working fine. AutoZone pulled the codes: P0174, P0171. I took it to a mechanic who said the codes were reading misfires, and the fuel mixture was rich (or lean I cant remember). I've done some research and some have suggested the cat converter, but I dont know what symptoms to check for on that, I called a dealer and they said it would be $150 to check and $1500 to replace if it was bad. Any suggestions what might be the problem or how I can narrow this Down and get it fixed? Thanks.

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    big greg is offline Cadillac Owners Fanatic
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    Check air plenum boot. Connects the intake to throttle body

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: 03 deville hard idle and bogging out lower speeds

    Your car has its own built-in code reader/scanner/memory system. Use the proper parts of the sticky post ^^^ "How to pull codes".

    P 0171 and P 0174 refer directly to lean mixture codes - caused by an air leak in the intake ducting at or after the MAF or a crack in the "plenum", that connector between the throttlebody face and the intake manifold snout.

    Pictures of the intake manifold and plenum in my albums. The Community tab, Albums, the red Seville. Your intake flex hose and airbox will be different from my STS, so adjust your thinking accordingly.

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    Ranger is offline Cadillac Owners Member
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    Re: 03 deville hard idle and bogging out lower speeds

    I'll make it unanimous. It's the plenum duct. No need top pay for a diagnostic.

    $1500 to replace it? Did they use a gun? Stick 'em up!

  6. #5
    big greg is offline Cadillac Owners Fanatic
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    Quote Originally Posted by Ranger View Post
    I'll make it unanimous. It's the plenum duct. No need top pay for a diagnostic.

    $1500 to replace it? Did they use a gun? Stick 'em up!
    Lol nice

  7. #6
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    Submariner409 is offline If it won't run, stick on fender vents
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    Re: 03 Deville hard idle and bogging out lower speeds

    The plenum and 8 intake manifold seals costs $15 + shipping from Rock Auto - the Dorman intake manifold connector. (Engine: intake coupling)

    GM labor time for intake manifold replacement is 2.5 hours - add 0.5 for the plenum.

    You can do the entire job with a basic metric socket set, patience, and an eye for detail. Many, many pictures of all the parts in my albums - the Community tab ^^^, Albums, the red Sevile.

  8. #7
    arduino is offline Cadillac Owners Member
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    Re: 03 Deville hard idle and bogging out lower speeds

    Thanks for the reply's. Its definitely the intake plenum boot. Submariner409 thanks for the details and picture link. I will do see if i can do it myself after i do my homework in the community tabs and albums. Will let you all know hoe it pans out when im done.

  9. #8
    Manic Mechanic is offline Cadillac Owners Fanatic
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    Re: 03 Deville hard idle and bogging out lower speeds

    $1,500 was dealer pricing for a new GM catalyst installed. Not the plenum boot.

    Vernon

  10. #9
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: 03 Deville hard idle and bogging out lower speeds

    Quote Originally Posted by Manic Mechanic View Post
    $1,500 was dealer pricing for a new GM catalyst installed. Not the plenum boot. Vernon
    ............ and I believe that price is for the complete, welded exhaust system - cat flange to tailpipe tips.

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