96 deville running rough when cold
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 96 deville running rough when cold in Past Cadillac Vehicle Discussion; Okay, this is a new issue to me...I wanted to get some more opinions before I just start buying things. ...
  1. #1
    galen717's Avatar
    galen717 is offline Cadillac Owners Member
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    96 deville running rough when cold

    Okay, this is a new issue to me...I wanted to get some more opinions before I just start buying things. 96 deville 84k miles, strong spark from each coil (disconnected each wire at the plug and get strong current), 50 psi fuel pressure holds steady, I can hear each injector ticking clearly with stethoscope. When started cold it runs roughly, once warmed up it's smooth as butter...could it just need new plugs? I do know that the car has only been driven 2k miles in the last five years and the plugs have not been changed. Anyone ever have this? It has ac delco platinum plugs in it right now.

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    basscatt's Avatar
    basscatt is offline Cadillac Owners 10000+ Posts
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    Re: 96 deville running rough when cold

    Quote Originally Posted by galen717 View Post
    Okay, this is a new issue to me...I wanted to get some more opinions before I just start buying things. 96 deville 84k miles, strong spark from each coil (disconnected each wire at the plug and get strong current), 50 psi fuel pressure holds steady, I can hear each injector ticking clearly with stethoscope. When started cold it runs roughly, once warmed up it's smooth as butter...could it just need new plugs? I do know that the car has only been driven 2k miles in the last five years and the plugs have not been changed. Anyone ever have this? It has ac delco platinum plugs in it right now.
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  4. #3
    rodnok01's Avatar
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    Re: 96 deville running rough when cold

    2k in five years is probably the issue... need to blow the carbon out of the old girl.

  5. #4
    galen717's Avatar
    galen717 is offline Cadillac Owners Member
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    My bad I forgot to mention that it had no codes.

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    Quote Originally Posted by rodnok01 View Post
    2k in five years is probably the issue... need to blow the carbon out of the old girl.
    Sea foam through the pcv?

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    I thought it strange it had no misfire code cuz it seems rough enough to have one

  6. #5
    basscatt's Avatar
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    Re: 96 deville running rough when cold

    Quote Originally Posted by galen717 View Post
    My bad I forgot to mention that it had no codes.

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    Sea foam through the pcv?
    ==============================
    Sea foam through the pcv?

    OH NO - now you've done it -

    be prepared to be SPANKED - or WORSE -

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    galen717's Avatar
    galen717 is offline Cadillac Owners Member
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    I guess that means no! What do u suggest to clean her out? Thanks by the way....

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    I just tried it again...ran rough for about five minutes once the temp gauge read about 160 (digital) I noticed it get smoother. Now it's running like normal at 192 degrees? ?

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    Re: 96 deville running rough when cold

    Take it out and beat the snot out of it.... keep the snake oils away from it .

  9. #8
    galen717's Avatar
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    Thanks rod

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    Re: 96 deville running rough when cold

    Quote Originally Posted by galen717 View Post
    Sea foam through the pcv?
    Bite your tongue.

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    Quote Originally Posted by galen717 View Post
    What do u suggest to clean her out?
    Go up to the Technical Archives at the top left of the page and read up on "Full Throttle Acceleration".

    could it just need new plugs?
    Yes, plugs and/or wires.

  11. #10
    dusty256 is offline Cadillac Owners Fanatic
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    Re: 96 deville running rough when cold

    Drive the thing.. dont abuse her but drive it ...these northstars love to be ran a few wot runs is great.

  12. #11
    galen717's Avatar
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    I appreciate all the help...I need to do the plugs anyway but I wanted some feedback first. I just took her out for another ride and it seems ok but I can still feel a slight roughness even when warmed up. I did a couple 3/4 throttle accelerations on the freeway. I guess I'll do the plugs and just drive some more. I will check out the thread you mentioned and post the results as well.

  13. #12
    galen717's Avatar
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    Update...got new plugs in early this morning. Didn't change the ride at all; still rough until driven for about five minutes then smoothed out by the time I got home. But it did throw a P0152 code. High voltage bank 2 sensor 1. Sound like a clue to anybody? Will a faulty 02 sensor affect the way the engine runs like this, then smooth out when warm? I've worked on quite a few N* and have usually found the problem fairly easily but this one has me stumped...Thanks in advance.

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    I checked the fpr and there were no obvious signs of fuel in the vacuum line..only a very faint smell. How do I check for leaky injectors?

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    I guess I should say too after driving it some more that it's a little more than just a rough idle. It doesn't really want to accelerate smoothly and it surges randomly as well until it really warms up..then smooth. I did feel a clear surge almost exactly when the light came on the dash if that helps.

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    I took it on two rides both times it started out rough and hesitating, surging; then MIL came on and it seemed to get smooth after that especially on the first trip...I was going about 35mph and I felt a little surge right when the light came on and it was smooth after that. Possibly open loop/closed loop related issue? Just throwing out ideas.

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    Re: 96 deville running rough when cold

    Sticky/dirty EGR valve?
    Vacuum leak?

  15. #14
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    I was thinking vacuum leak as well but it goes completely away after a while. Also that wouldn't explain the code for running rich...I will have to check the egr but how much, and when does it cycle open and closed cuz it is a constant rough run until it's warmed up completely. Still brainstorming!

  16. #15
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    Re: 96 deville running rough when cold

    Well, here's one off the top of my head vacuum scenario. Loose rubber PCV grommet in the rear cam cover. It heats up and expands, sealing the vacuum leak.

    I forget exactly when the EGR is cycled on, but I know that there should be no EGR flow at idle. That will cause a stall (or rough idle if it is a small leak). I think EGR flow is also disabled during acceleration, but not positive.

    Running rich? Have you checked for a leaky FPR?

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