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spark plug gap 1mm or 1.1 ?

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1mm gap plug spark
8.9K views 4 replies 5 participants last post by  shortlid  
#1 ·
I have a 2.3 turbo fitted with BCPR7ES-11 plugs which are pre-gapped to 1.1mm.

I have read on another forum that these should be set to 1mm or less.

Should I change the gap - what problems will I have if I leave as is ?
 
#3 ·
Since 1.1mm is the absolute top end of the spec. according to Saab, I like to gap them to around 1.0mm or even a bit less on the principle that they will stay within spec. for longer. Otherwise they will be out of spec. almost as soon as you use them. On my CSE with a full Saab service history, the plug gaps at the next service (which I did myself) were 1.4mm! Needless to say, the DI cartridge failed shortly after.

The only exception I make on the gaps is that I use 1.1mm on my Aero as it seems to run better with the larger gaps. However, I do tend to check them very regularly and adjust them to keep them within spec.
 
#4 ·
It it a much discussed topic, but I recently took my plugs out to check them and while they were out I gapped them at 0.9 just to see, and I think the car does run a bit better. It certainly idles more smoothly.

Also, I don't trust the "pre-gapped" idea, since you never know how they've been handled before you get them, so I always check anyway.