Car: 97 legacy gt 2.5l Modifications: none Problem Description: after starting car it runs fine until it warms up, it then stumbles/misses and low on power in low rpms. I had a p0400 code, pulled the egr valve and cleaned it and replaced gasket. Went to orileys cleared code, another code came up p0301 misfire cyl 1. I just pulled the #1 plug still clean and is gapped at .o40 Recent Modifications/Maintenance: head gaskets, timing belt, water pump, ignition coil, and battery.
Compression test time on that cylinder, probably a burned valve, its not super common, but they are probably second behind the wrx at burning an exhaust valve.
Well the head on that side is almost new, 6 new exhaust valves and 4 intake, along with valve seals and valve lash set, I'm thinking it's fueling now, either injector or front o2 sensor. The reason I think it could be that on start up it runs fine until it goes to closed loop. Just throwing ideas out.
i had the same thing on my 99 lgt. i had 2 intake valves on cyl 4 with a very slight bend that it would drive down the highway nice and smooth but when you stopped at a light it would miss constantly