96 STS running rough code P 0174
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Cadillac Seville / Cadillac Eldorado Forum Discussion, 96 STS running rough code P 0174 in Past Cadillac Vehicle Discussion; I'm having issues with running rough. Code p0174. Fuel pressure sets at 45 paid and I've replaced both upstream o2 ...
  1. #1
    ffseville is offline Cadillac Owners Member
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    96 STS running rough code P 0174

    I'm having issues with running rough. Code p0174. Fuel pressure sets at 45 paid and I've replaced both upstream o2 sensors. Had a leaky fuel pressure regulators but replaced it. Anyone got any answers?

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    basscatt's Avatar
    basscatt is offline Cadillac Owners 10000+ Posts
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    Re: 96 sts running rough code p0174

    Quote Originally Posted by ffseville View Post
    I'm having issues with running rough. Code p0174. Fuel pressure sets at 45 paid and I've replaced both upstream o2 sensors. Had a leaky fuel pressure regulators but replaced it. Anyone got any answers?
    ---------------------
    you have a big vacuum leak somewhere -

    get a can of carb cleaner - put the little spray hose on it -
    and - with the engine running -
    spray the carb cleaner around the intake manifold -
    pay particular attention to the 90* elbows of the PCV hoses -

    when the idle speed changes - you found the leak -

  4. #3
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 96 sts running rough code p0174

    That code is for bank 2 so pay particular attention to the front bank area.

    P.S.
    and for future reference help us help you and always post the code definitions along with the codes. Most of them are not memorized. This on is an exception.

  5. #4
    ffseville is offline Cadillac Owners Member
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    Thanks for the info. Just know that with 190k that there is the possibility of clogged injectors also. No vac leaks seen or heard. So...just hoping someone has had this occur and had a simple fix. If you have any more info, please feel free to drop a line. Again, thank you.

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    vincentm's Avatar
    vincentm is online now Cadillac Owners Connoisseur
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    Torn plenum duct?

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: 96 STS running rough code P 0174

    96 does not have a plenum - they use a silicone O-ring seal between the throttlebody and intake manifold.

  8. #7
    vincentm's Avatar
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    Quote Originally Posted by Submariner409 View Post
    96 does not have a plenum - they use a silicone O-ring seal between the throttlebody and intake manifold.
    Ah, perhaps that could be inspected by the OP?

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    Ranger's Avatar
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    Re: 96 STS running rough code P 0174

    Those never leak.

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    Submariner409 is offline If it won't run, chrome it
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    Re: 96 STS running rough code P 0174

    MAYBE the ol' GumCutter squirt try, but in any event, the intake manifold would have to come off to repair either type of connection if a vacuum leak shows up.

    As Ranger posted, the older O-ring style is not known for leaks.

  11. #10
    stoveguyy is offline Cadillac Owners Connoisseur
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    Could pull intake and check plastic gaskets. The silicone does flatten over time. I removed my intake for head job and noticed silicone seal was flat. But than the valve cover gasket seal was perfect. You would think VC seals would fail first?

  12. #11
    mycaddystinks is offline Cadillac Owners Member
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    Re: 96 STS running rough code P 0174

    Check to see if the PVC nylon tube isn't cracked it'll run from the front right of engine under vanity cover to back left top of engine. When you replaced fpr it might have broke at the back left plug into the engine. I think it's the PVC valve on the lb. mines cracked I taped it but after a whole it came off and started running kinda bad, had to replace. Also could be egr valve sticking. Does it ever kick down when idling at a light like its going to stall then go back to normal idle? That valve sticks then kicks open quickly and stutters it, cleaned mine and never did it again.

    Do not ever put gum out in that car, you'll have more problems, put it in mine had to run a few tanksof high octane with some heet in it for the extra alcohol to get it back to running right. I figure someone will say I'm wrong but try it yourself, I'm just telling you what I did on MY car. Good luck were all pulling for ya.

  13. #12
    ffseville is offline Cadillac Owners Member
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    OK. Found pcv elbow cracked. Replaced it. Slight improvement, but still not right. Now I have code p0171 and p0174...both banks lean. Beginning to seriously consider fuel injectors as I do not have any vac leaks. I have checked and rechecked fuel pressure and vac leaks. Any other advice?

  14. #13
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    Just for giggles, clean the MAF.

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    basscatt's Avatar
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    Re: 96 STS running rough code P 0174

    Quote Originally Posted by ffseville View Post
    OK. Found pcv elbow cracked. Replaced it. Slight improvement, but still not right. Now I have code p0171 and p0174...both banks lean. Beginning to seriously consider fuel injectors as I do not have any vac leaks. I have checked and rechecked fuel pressure and vac leaks. Any other advice?
    -------------------------


    I do not have any vac leaks
    you said that before - yet you just found one -

    try the carb cleaner method - it works -

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    Re: 96 STS running rough code P 0174

    It ain't fuel injectors.

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