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Old 12-02-2019, 09:57 AM   #1
Scooby Newbie
Member#: 442552
Join Date: Mar 2016
Default Misfire when cold outside

My 2008 Impreza 2.5i has developed a weir misfire issue only when its cold outside (and given that we now have snow on the ground in Minnesota it won't be warm again for a while). It will throw random cylinder 1 & 3 misfire codes until there is some heat in the engine, then it runs fine. I can smell unburnt fuel in the exhaust so I know the injectors are firing. I haven't done much more than make sure the coil pack is fully plugged in and the wires are fully plugged in yet since I haven't had a lot of time. I'd just like some things to look at to start.

Last summer I put head gaskets in it, including a new radiator cap which being aftermarket failed already. But it still ran fine even when cold up until this point. Took it to a local shop since I thought it needed head gaskets again, the put a new cap in it and this is when it started misfiring. This cap also went out (again aftermarket) so I put a brand new Subaru cap on it and that is fine now.

The plan this winter was to have my wife take my car once a week to get some more miles on it, but until I figure this out I don't want to let her take it. I don't want to just start throwing parts at it either. I'm currently running E3 Spark Plugs in it, could these be part of the problem? When I put the head gaskets in it, I missed a couple grounds, do I need to check the ones running to the heads to make sure they are tight?
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