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  1. #11
    Saab Fan
    Join Date
    11 Mar 2011
    Location
    Southern New Jersey
    Posts
    7
    Saab(s)
    2001 9-3 Viggen Convertible
    Thumbs Up:   1
    The bad lifter could be causing the noise, but the broken plug and low compression indicates to me that it could be a piston problem. If anything the valve with the bad lifter would not open fully. #4 could have leaned out fuel wise and cracked or melted part of the piston. A small piece of the piston could have damaged the plug, possibly a lean fuel mixture could have too. It is known that #4 piston will be damaged if the MAF causes a lean fuel mixture. Read a few posts concerning this over the years. I'd consider pulling the head or getting a cheap ebay bore-scope/USB small camera to check out #4 piston for damage or just pull the head. I'd also pull the pan and check for sludge. Does it have the PCV #6 update?

    You might want to re-torque the head bolts to see if that brings up #4 compression to match the others.

    I bought a 2001 Viggen convertible earlier this year with 178k on it to restore and tinker around with. The car runs well but I have limited service history and it does not have the PCV #6 update. Drove it a few times but I am waiting until I drop the pan before I drive it again.

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  2. #12
    Saab Enthusiast
    Join Date
    19 Jul 2015
    Location
    Charlottesville, VA
    Posts
    217
    Saab(s)
    1997 NG 900 SE
    Thumbs Up:   40
    Suspect burnt exhaust valve. Try leak down test before pulling head.


    Sent from my iPhone using Tapatalk

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  3. #13
    Saab Fan
    Join Date
    09 Sep 2018
    Location
    Montana, USA
    Posts
    7
    Saab(s)
    1999 Viggen
    Thumbs Up:   0
    Hey all,

    Another update. I pulled the spark plug from Cylinder 4 and used a boroscope to inspect the cylinder wall and piston head. What am I seeing? Bad piston? Bad cylinder wall?

    Next steps?

    Thanks,
    John.


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  4. #14
    Saab Fan
    Join Date
    11 Mar 2011
    Location
    Southern New Jersey
    Posts
    7
    Saab(s)
    2001 9-3 Viggen Convertible
    Thumbs Up:   1
    Tough to tell from that. But the cylinder walls do look scored to me. The marks on the cylinder walls seem to match marks on the top of the piston. Maybe post a bit more?

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  5. #15

    Join Date
    08 May 2015
    Location
    Bend, Oregon
    Posts
    2
    Saab(s)
    2000 9-3 Viggen Convertible
    Thumbs Up:   0
    Looks like the knock is piston slap. Notice the change in the width of the gap between the wall and the piston? At what appears to be the widest gap is definitely scoring. Based upon that damage and the lifter damage, that side of the motor is getting enough oil.

    EDIT: While my original thought is a possibility after a couple beers my idiot light went on. How old is your IC? Or miles since it was replaced, if ever? I'm leaning more towards pre-ignition which would explain the initial lag and subsequent carnage in such a short period of time and burns any oil out of the chamber, hence no lube and quick damage. Not likely the ECU, and oh how we love those throwaway IC's that slap you as they're leaving. And if that thing was advancing on #4 to cause pre-ignition, you got off lucky.

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    Last edited by warhoop; 23 October 2018 at 12:32.

 

 

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