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Old 11-18-2003, 04:13 PM   #2
Scooby Newbie
Member#: 48742
Join Date: Nov 2003
Location: Boston
2002 BMW M3
1997 Subaru Legacy

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Hi there,

Piston slap in modern engines is often caused by deposits on piston heads in emissions reducing engines that have a piston clearance of less than 1mm at top dead center. It likely is not caused by metal to metal impact.

It may be a little pricey for an additive (~$10), but the first thing I would do it add a bottle of Chevron Techron to your next fill up. It does wonders for removing deposits fuel injector AND piston head deposits. If possible, fill up with Chevron Supreme too.

Repeat if it still doesn't go away.

You should notice your piston slap disappearing and more power since your engine probably has been retarding the spark to compensate for the increased compression too.

Check this link out for more info:
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