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Old 09-18-2017, 03:16 PM   #1
940 16 valve
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Join Date: Oct 2005
Location: Calgary, Alberta
Default Help reading spark plugs

Hey Crew

The 16v turbo has been idling rough for some time. Started doing preliminary investigations yesterday before pulling the head (hopefully tonight). Compression check came up 145/150/150/150. Had a look at the plugs and thought the difference between them is pretty interesting, but I don't have a lot of experience reading plugs. I did some reading online, but I still don't feel like I have a confident idea what would explain this.
Setup is stock B234 with 16T running Fred's 16v chips @ 12lbs boost on Saab APC. green giants, stock FPR. Have been running 3" AMM which does have it a bit lean at onset of boost.

Cyl 1 is at top of image, 4 at bottom.
1991 940 - stock b234+t -retired
1989 760 - T5 +T5 swapped

Last edited by 940 16 valve; 09-18-2017 at 08:53 PM..
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