2006 Legacy GT Powertrain Cylinder Misfire Code

[ki6fff]

I have an automatic 2006 Legacy GT wagon with the turbo. It has about 185,000 miles on it. I just had a complete rebuild of the engine by Outfront Motorsports in Buena Park. They installed forged WRX pistons, ARP rod bolts and WRX engine mounts as upgrades for helping the engine last. They did a great job on the rebuild and are very helpful if I have any issues. My only concern is that I have piston slap in cylinders 2 and 4 but it doesn't effect the engine other than noise.

 

Under hard acceleration, like merging onto the 91, my check engine light flashes and the transmission holds the gear up to redline. When I check the codes using my TORQUE app on my phone, I get P0304, and P0303, Powertrain cylinder misfire detected. Outfront can't seem to replicate it when they have the car. Also, sometimes the car is hard to start after I clear the code.

 

What could be the cause and how to I remedy this issue?

 

PS, The turbo has been rebuilt within the last two years; I use Rotella oil and change it at 4k miles.

 

 

 

[1 Lucky Texan]

hard to say but, could be wires or maybe a coil issue.

 

I think you may need to have the ECU read for the fuel trims. If it doesn't run well on the factorey map, like after a reset, that kinda points to a major correction the ECU is having to make in A:F or timing or ???

 

do you run high octane? if not, try a tank or 2 and see if it's better - maybe the car is knocking ? Knock sensors go bad and are cheap to change out.

 

I'd also pull the covers and look for slipped cam timing.

[ki6fff]

Thanks, yes, I run 91 or better every time. I'll look into the knock sensors. The plugs, wires, and coils have all been replaced during the rebuild.

[1 Lucky Texan]

check the timing.

 

using OEM or NGK wires?

[Fairtax4me]

How long since the rebuild? Have the plugs been changed since then?

I would pull the plugs first and see how they look.

If the car has COPs make sure the boots are ok, and look for evidence of burns (white powerdery markings). Also check the springs that clip onto the top of the plugs for any corrosion or burning.

 

If it has plug wires and a coil pack move the wires around and see if the misfire follows. Also check the ends for corrosion or burning at the plug and the coil.

[ki6fff]

The rebuild is less than 3 months old with less than 7k miles on the new engine.

[ki6fff]

With NGK plugs and wires