1990 Sedan Deville Valve Job
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Northstar Engines and System Technical Discussion Discussion, 1990 Sedan Deville Valve Job in Cadillac Engine Technical Discussion; Hi, I have a 1990 Sedan Deville I'm presently getting about 18mpg on the highway instead of the 23 I ...
  1. #1
    sgpsp17 is offline Cadillac Owners Member
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    Nov 2003
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    1990 Sedan Deville Valve Job

    Hi, I have a 1990 Sedan Deville I'm presently getting about 18mpg on the highway instead of the 23 I used to. My engine also seems to be struggiling to get gas to it. Sometimes it doesn't get any gas to it at while I am going up hill and it will die out. I was told it was the valves and I need to get a valve job done. I was wondering if could be anything else? Also does any body no an average price for a valve job? Or how much it would cost to replace a V8 4.5L engine? It would be greatly appreciately for a response.

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  3. #2
    zonie77 is offline Cadillac Owners Connoisseur
    Automobile(s): 94 ETC,97 STS
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    Re: 1990 Sedan Deville Valve Job

    Who told you it was a valve job and what did they base that on?

    I'd start with fuel pressure first. If you havn't changed the fuel filter in a long time try replacing that first. Have the fuel pressure checked if the filter doesn't fix it. Elec fuel pumps can get weak or the filter in the tank may be clogged so it is supplying a limited amount of fuel.
    Elec problems shouldn't cause it to die but could make it shake going uphill.

    Normally if you need a valve job it will be idling rough. If it idles smoothly it isn't a valve job.

    Head gaskets start off by causing overheating in a Northstar.

  4. #3
    sgpsp17 is offline Cadillac Owners Member
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    Re: 1990 Sedan Deville Valve Job

    This is in regards to my 90 Sedan Deville again

    This is what they said "
    This is an attempt to get your car running better. I had one hell of a time
    checking compression on the back cylinders(just wasn't room to fit the
    compression guage tightly), but did notice some markings with a triple cross
    above your 6th spark plug. I'm assuming that is where the other mechanics
    decided you had a bad valve. So your car never will run like new, but if we
    can clean out the sludge, than maybe the compression in that cylinder will
    increase and you can get by. Rislone is an additive to help older cars
    before the valve starts leaking, but I'm just hoping if there is not too
    much wear, it may help. Afraid there is no other way to fix a worn valve
    except by taking off the head and replacing the worn parts. $$$$ I'm hoping
    we can get this car running good enough that you can eventually get some
    good money out of it or trade it?? Will take time though. Yes it should be
    driven(til engine warms) with frequent oil changes(2-3000 miles max). Also
    that 6th cylinder spark plug will continue to foul out and need to be
    cleaned every 2 weeks(you will need a wire brush and ratchet wrench) until
    the sludge finally is gone. 2nd choice is simply getting used to driving it
    with 7 cylinders hitting and poor gas mileage. This is all under the
    assumption that nothing else will go wrong in the mean time? Think
    positive! Jim"

    I do know this person

    If some could give me more advice on what to do? Or if someone could tell me how much a valve job costs? Or anything like how they're doing? It would be great thank you much.

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