Cyl #1 low compression
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Cadillac Seville / Cadillac Eldorado Forum Discussion, Cyl #1 low compression in Past Cadillac Vehicle Discussion; I have a hard miss at start-up until the (4.9 Seville) engine warms up good. My mechanic says #1 cyl ...
  1. #1
    unclebig is offline Cadillac Owners Member
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    Cyl #1 low compression

    I have a hard miss at start-up until the (4.9 Seville) engine warms up good. My mechanic says #1 cyl has only 90 lbs, could be excessive carbon since the car is very in-town used. Said to blow it out good on the highway. He put a can of Sea Foam in it, can I add something else (with the SeaFoam)to give it an extra cleaning boost? Also is there a recommendation to regularly add something to the fuel...how about denatured alcohol? All other cyls have 140 lbs...he says if I can get 15-20 more, it would run OK.

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  3. #2
    basscatt's Avatar
    basscatt is online now Cadillac Owners Master
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    Re: Cyl #1 low compression

    Quote Originally Posted by unclebig View Post
    I have a hard miss at start-up until the (4.9 Seville) engine warms up good. My mechanic says #1 cyl has only 90 lbs, could be excessive carbon since the car is very in-town used. Said to blow it out good on the highway. He put a can of Sea Foam in it, can I add something else (with the SeaFoam)to give it an extra cleaning boost? Also is there a recommendation to regularly add something to the fuel...how about denatured alcohol? All other cyls have 140 lbs...he says if I can get 15-20 more, it would run OK.
    -------------------------------
    90 on one and only 140 on the rest is NOT A GOOD SIGN -
    sounds like a tired motor -

    how many miles on the car -

  4. #3
    unclebig is offline Cadillac Owners Member
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    Re: Cyl #1 low compression

    It is a 1991 SEVILLE WITH ONLY 72,000 MILES (not 172,000), mostly in the neighborhood !

  5. #4
    Submariner409's Avatar
    Submariner409 is offline If it won't run, slap in a big stereo
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    Re: Cyl #1 low compression

    The motor has been neglected (not driven) and is "lazy". Entirely possible that the piston rings are really gummed stuck - about the only possibility in such a low-mileage low-speed babied engine. If the car is driven short-hop locally, never thoroughly warmed up, then I shudder to think of what the inside of the engine really looks like.

    Various snake oils and magic potions in the gasoline will do just about nothing for stuck rings. That requires a specific engine-off-spark-plugs-out chemical treatment, engine run, and oil/filter change by a GOOD shop.

    Denatured alcohol (methanol) will promptly eat every piece of rubber and pump guts in the fuel system. Most fuel already contains 10% ethanol, a powerful solvent and detergent. (Ethanol - whiskey grade - is "denatured" by adding small amounts of gasoline to the tank truck load - fuel grade ethanol is eminently drinkable, so it is spiked to prevent "moonshining" with it.)

  6. #5
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Cyl #1 low compression

    I find it hard to imagine that only one cylinder would have stuck rings, but I suppose stranger things have happened. You could try the Northstar WOT procedure (Technical Archives) or the Northstar ring cleaning procedure (Northstar forum Sticky post)..

  7. #6
    unclebig is offline Cadillac Owners Member
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    Re: Cyl #1 low compression

    Thanks all: I did put a can of Sea Foam in it earlier today, and after a half-hour it actually started to run more smoothly !!?? Got the oil changed, and ran it about 40 miles at 70 MPH, and still is holding. If there is a relapse, I will look into the advised procedures above. Thanks Again. UncleBig

  8. #7
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Cyl #1 low compression

    What's the compression in #1 now?

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