Hi all

For a while now I've had a very intermittent misfire that might occur once or at the most twice a day, many kilometers apart, or may not happen at all for hundreds of kilometers. It happens only at freeway (80kmh - 110kmh) speeds, and always when under very low, cruising load. It's a single misfire, that causes a brief increase in RPM and slight hesitation. However today, I encountered it once on the freeway, but also twice when sitting at a stop light and attempting to pull away slowly.

Some specifics:

Highway AFR ~ 14.5, idle - 12.5
Brand new PFR7B plugs went in about 1000km ago
New 1000cc injectors and fuel pump ~ 10K km ago
Unknown km individual coil on packs installed same time as pump/injectors.

The fact that I have no idea how many kms were on the packs when I installed them (bought from JWS when I built my engine) lead me to thinking it's possible one perhaps breaking down, in which case I'll just buy a brand new set of four, but other than that, I'm not sure where the problem is coming from.

Any internetz diagnosis welcome

Cheers, Alex.

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Air is for pussies.

No internet diagnosis from the gurus?

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Air is for pussies.

As the A/F readings are higher at low throttle and idle and also running 1000cc injectors, the plugs could be fouling causing the missfire.
Might simply be a case of trimming the low load fuel tables.

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MY00 WRX. 89 Prelude. 99 CRV