Quote:
Originally Posted by blsfrs
Is it possible that an inaudible exhaust leak could throw off your afr? Slight crack in the header? I saw a post where a leak at the header/overpipe gasket caused an afr problem. A small leak would be hard to hear over the noise of a Russian tractor engine. It's relatively easy to check and replace gaskets.
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That's possible. The stock manifold halso has 2 flexible sections that I've known to crack on foresters and outbacks, but on an fr-s, those should be on 1-3 and not 2-4. Also, since it's being detected via crank speed, it's probably reasonable to assume it's not a situation of combustion being fine and then sucking in air in the exhaust path, one of the boys isn't doing the same work as the other 3.
OP, it's
probably not your plugs, but if you want to do them go for it, sometimes having one less thing to worry about, is one less thing to worry about
swapping coils when you've got a dodgy issue should be a given, but again,
probably not your issue.
Since it's a a P119
F it's doing it on direct injection, which would be a pain to swap around. My first instinct would be to put an oscilloscope on the injectors to get a feel for them without taking things apart but that's not a tool you can just whip out of your pocket, so you might just
have to move them.