96 deville running rough when cold - Page 2
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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; Oh I see so the egr could be stuck open...yes I did check the fpr as well as I could. ...
  1. #16
    galen717's Avatar
    galen717 is offline Cadillac Owners Member
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    Oh I see so the egr could be stuck open...yes I did check the fpr as well as I could. I could see no signs of fuel in the vacuum line and I also removed it and tried to suck air through it as hard as I could using the vacuum line, but got nothing. I just came from pullapart and got an 02 sensor and another fpr. I will try each of them and see what happens. Thanks ranger!

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    Oh yeah I also removed the pcv at the throttle body and plugged it with my finger but there was no change...I tried that yesterday. Any ideas on the open/closed loop operation? That almost seems like the time it starts to smooth out when switching from open to closed...just thinking...

  2. #17
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    Re: 96 deville running rough when cold

    If you could not suck air or fuel through he FPR, don't bother changing it.

    Have you checked all the other vacuum connections as well as the manifold over pressurization valve?

    Not sure what to say about open vs closed loop.

  3. #18
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    I swapped 02 and took it for another ride and it did the same thing. As soon as I hit 174 degrees it surged a little and the light came on at that exact moment and it was running better. Same code different 02 sensor so I'm thinking something is causing a rich mixture and as soon as it switches to closed loop it compensates and immediately runs better. How can I check for leaky injectors? You were right about the fpr I swapped it anyway when I got back but it made no difference.

  4. #19
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    Re: 96 deville running rough when cold

    Quote Originally Posted by galen717 View Post
    How can I check for leaky injectors?
    http://www.cadillacforums.com/forums...-injector.html

  5. #20
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    Thanks ranger already did it and got nothing! Here's the update: took it for another ride and it threw P0151 now saying lean on the same 02 sensor. So I put in a third new 02 sensor and took it for another ride about 10 miles and got no code...it ran smooth as butter too. I am letting it cool down to try it again later. I also cleaned out the TB, MAF, and IAC just to be sure. So I'm thinking maybe it was the 02 sensor to begin with...can they cause a rough running condition like that?

  6. #21
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: 96 deville running rough when cold

    IF you unduly twist, bend, or stretch the wiring harness pigtail or contaminate the tip of a new O2 sensor it can be permanently damaged. The damn things are sensitive and cannot take abuse in handling. A simple kink in the wiring can render a new sensor unusable.

    EGR is normally locked out until emissions go closed loop. It then operates at part throttle and cruise in order to dilute the incoming fresh air charge and slow down combustion. EGR is disabled, as are most emissions controls, during a WOT full power run. It does not bleed exhaust gas at idle.

    Your emissions systems change loop at between 135 and 160 degrees coolant temperature depending on ambient temperature PCM/ECM input.

    If your change in engine operating characteristics occurs between about 10 and 11 o'clock (or the 2nd and 3rd bars) on the temp "gauge" there's some sort of hiccup in the loop change engine operation.

  7. #22
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    Thanks for chiming in sub...the funny thing is the driving improved as soon it goes closed loop. Yeah I noticed the change right at about 160-175 (digital gauge in the base 96 deville) it runs rough at startup then about the time it goes closed loop it improved and was smooth the rest of the time. But now that the new one is in there it drove really good the whole time and gave no new codes. I am giving it time to cool down then try again. Will let you all know what happens.

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    Does the ecm program defaults for open loop operation based on previous 02 sensor readings? Could that cause bad operation in open loop?

    I took it out for another highway ride and it seemed fine start to finish! It wasn't all the way cool though I guess I'll know for sure in the morning. Thanks for all the input everyone.

  8. #23
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    Tried it this morning and it was good! A little hiccup when backing out but that's probably cuz I didn't let it warm up properly. It rode smooth the whole time.
    So here's the recap: ran rough, hesitated, etc. until it reached closed loop temperature. Then ran smoothly. Had DTC P0152, then P0151.

    Cleaned TB, MAF, IAC, replaced 02 sensor bank 2 sensor 1. I think it just needed a good cleaning and to be driven some more. Thanks again for the help.

  9. #24
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    Re: 96 deville running rough when cold

    Yea I bet that 2nd O2 sensor was junk also(been there ) or wiring was iffy. Hopefully it runs better for you now and don't forget take her out and heat it up couple times a month.

  10. #25
    galen717's Avatar
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    Will do!

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