1988 Deville Very intetresting Idle
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 1988 Deville Very intetresting Idle in Past Cadillac Vehicle Discussion; I have been having some trouble with my car at idle for a few months I guess. Rather than keeping ...
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    FireBlazed's Avatar
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    1988 Deville Very intetresting Idle

    I have been having some trouble with my car at idle for a few months I guess. Rather than keeping a steady, strong idle... Sometimes it goes tthrough an oscillation going from strong to weak then strong to weak etc...making a sound that goes sort of..----____----____----____....if you could picture that curve with engine noise (lol)...now my question is what do you think this is the cause of? Fuel filter and lines have been replaced, seafoamed until completely cleaned a few times, and the gas tank is near full...

    With all that being said my only guesses are, 1) fuel pump 2) needs new spark plugs and wires or 3) needs a new fuel pressure regulator

    Any advice or experience with this problem on a 4.5 Deville?

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    MoistCabbage's Avatar
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    Plugs and wires would cause a misfire, not surging/loping idle. Fuel pressure problems would cause a rich or lean condition, hard starting, a lack of power....etc, but again, not your symptoms. Check of your ISC motors plunger is moving in and out and causing the loping. (you'll see plunger up against the throttle plate.

    And STOP pouring seafoam into your engine.

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    PineyJustice is offline Cadillac Owners Fanatic
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    Re: 1988 Deville Very intetresting Idle

    Seafoam is known to foul plugs pretty badly, also mess up your oil, if you seafoamed your engine new plugs and new oil should have been one of the first things you did afterwards. That said I have seen seafoam smooth out some really rough running engines, it does a pretty good job at removing carbon buildup. The only problem is that it blows that carbon all throughout your engine afterwards wreaking havoc on your plugs o2 sensors catalytic converter and I have even seen a few reports of it ruining coil packs (No idea how it did it, but it apparently did it).

    I'd do the plugs as a precaution, check the ISC, check the throttle body and go buy a can of MAF cleaner.

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    FireBlazed's Avatar
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    Alright thanks for the heads up I was planning on doing the plugs and wires...I mean it smoothed out the idle pretty good after doing that but it wasn't that long ago so I should be able to take care of the plugs and stuff pretty soon

    ----------

    Also MC, check out my pics of the car being that you showed some interest in it.

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    Re: 1988 Deville Very intetresting Idle

    Sounds like a vacuum leak to me.

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    Re: 1988 Deville Very intetresting Idle

    I'm surprised and quite disappointed
    that nobody suggested CHECKING FOR CODES -

    sometimes you guys see SEAFOAM in a posting -
    and all you see is RED - and all logic disappears -

    I have even seen a few reports of it ruining coil packs

    really? are they soaking coil packs in it?

    if you knew ANYTHING about cars -
    you wouldn't even bring such NONSENSE up -
    even if you did read some ridiculous report -
    much less a few reports - doubtful -

    Seafoam is known to foul plugs pretty badly,
    also mess up your oil, if you seafoamed your engine
    new plugs and new oil should have been
    one of the first things you did afterwards


    MORE PURE NONSENSE

    next you will blame SEAFOAM for causing genital worts -

    OK - off my soapbox -

    check for codes -

    look at the throttle body -
    open the throttle butterflies - is everything clean

    look at the bottom of the throttle body -
    are those 2 small holes clear or plugged up

    post back with your results -

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    Quote Originally Posted by basscatt
    I'm surprised and quite disappointed
    that nobody suggested CHECKING FOR CODES -
    Lol, I could have sworn that I did. Was in a rush when I posted, must have slipped my mind completely.

    FireBlazed. There's a thread on how to pull codes at the top of the FWD Deville/Fleetwood page. Study it, and post any codes you may find, AND THEIR DEFINITIONS, here (there's a link within the sticky with code definitions, your car is OBD I)

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    Re: 1988 Deville Very intetresting Idle

    Quote Originally Posted by basscatt View Post
    next you will blame SEAFOAM for causing genital worts -
    If you feel comfortable taking that risk, by all means carry on.

    Not saying it should never be used, just that care should be taken. You are basically blowing a lot of carbon buildup out of the upper cylinders which can migrate elsewhere, this is why the only time I ever seafoamed a car was right before I was planning on changing the plugs and oil anyways.

    These were my thoughts beforehand, and a local shop pretty much echoed this when I mentioned seafoam to them. Checking for vacuum leaks is a good idea though.

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    Re: 1988 Deville Very intetresting Idle

    this post is timely because just this week, I've been having the same issue with my '88 Fleetwood FWD. I drove over 100 miles Sunday and filled up before coming home. Monday morning, I had the idle problems you're describing above. First thing I did was check for codes and there were none. I took it in Tuesday and they said the fuel filter was pretty stopped up. It was replaced and later this week, at start up, i've noticed the same issue I had Monday. Not quite as bad. I'm not sure if it's bad gas or what. Fuel filter had been changed a year ago along with the fuel pump. Plugs and wires are all new in last year.

    If it is the ISC motor, would a code be thrown? I will look for vacuum leaks this weekend although my shop didn't find anything wrong when I took it to them.

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    Re: 1988 Deville Very intetresting Idle

    There is only one OBDI ISC DTC.

    P030 (E030) .................................................. . ISC RPM out of range

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    I believe there's also idle high/low under ISC, or incorrect idle under ISC.

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    The throttle body is definitely 100 percent clean. I mean I'm not sure if under the flaps it's perfect I didn't give it a good look last time
    I checked...my fuel rail and filter are new since the old ones had nasty rust...I didn't run the codes but I'll try tomorrow...vacuum leak where possibly? I mean what should I look at the break booster? Or pcv hose? Or something else?

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    Re: 1988 Deville Very intetresting Idle

    EVERY vacuum hose connection.

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    I just wanted to say that I tried to pull the codes idk If I made a mistake or not but this is what happened. I held off and warmer...the entire green display lit up and what happened the. Was it turned to the .7.0 on the FDC. For the record on the upper dash where the speedo is, only the service soon, and service now lights illuminated. Then on the right side Econ flashed, so I pressed Econ and the only thing that came up was F.8.5. Does any of this mean anything or is any of this abnormal?

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    Re: 1988 Deville Very intetresting Idle

    I think the ISC is compensating for something or is defective. Once you figure out the codes that should help. If the only code is isc out of range then I would adjust it and make sure the EGR tubes are clean. I think this write up on getting codes is easier to understand so try it again and see what comes up.

    http://www.cadillacforums.com/forums...x-engines.html

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