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Hi guys thought maybe I'd ask here for some help I have a 2005 wrx stock motor with some bolt ons. The cars is giving misfire in cylinder 2 and 4 and also o2 sensor code. It's not muffing smoke or shaking the car horridly. It's noticeable but barley shakes engine a bit.
Things ive don't are cleaned MAF sensor, new air filter and checked cylinder 2 coil pack and spark plug. The spark plug seems good no oil or fuel.
Mods are
Vf39 sti turbo
Sti pink injectors
Sti intercooler
Cobb turbo back exhaust
Also have boost gauge and at idle seems constant and doesn't bounce like if it had a boost or vacuum leak
What tool access do you have? Can you do a relative compression test? I've heard of Subaru valve guides moving and causing sealing issues but not sure it effects the wrx motor. Another thought is confirm valve timing. From memory 2 and 4 are the same side? I'm wondering if someone has done a belt and that's effecting one bank.
With a 2 cylinder misfire on the same bank you really have to look to possible causes that are common to both cylinders. Also keep in mind misfire counters can point to the wrong cylinders.
As Matt.white has said a compression test might be a good move, depending on access to the spark plugs and tools available an ordinary compression gauge test or a cylinder leak down would be my choice.
A leak down test is the best compression for pin pointing what parts are causing any loss of compression.
I have never done the cam belts one of these but I do know the cam timing can be tricky to set up but my thinking keeping in mind this is a modified engine is valve seat recession or a head gasket issue.
What O2 sensor codes are you getting ? lean O2 senors codes are often just a sign of misfire due to other causes or it could point to a genuine lean condition causing the misfire. Diagnosing based on codes alone can bite back you need to look at live data prefferably in a graph form , focusing on O2 sensor, fuel trims, and MAF output Don't be too quick to rule out a vacuum leak.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
I'm with Andy and Matt about a possible timing issue on bank two. If the outside timing covers are easily removed, then it may be easiest to just pull them and manually check the marks.
I don't have tools to do a compression test I think I am going to check my driver side timing marks for intake and exhaust cams if they are off I'm going to move them to proper markings. Hopefully that's my problem
swap the coils from no 2cyl to no 3 clear codes test drive and see if it changes the codes to a diff cylinder and maby put some new plugs in depends on how worn the tips are .
I'm sure you already know that those engines need a solid tune when you turn the wick up. They do not like any detonation and easily break ring lands. I would start with a compression test and move forward from there. Sorry to be a "Debbie downer" but I have been down this road many times. Goodluck!
So update I didn't look at timing garage was full. But I did scan the car again and I got only 1 fault now code po420 Catalytic System Efficiency Below Threshold (Bank 1)
And today I started it to move the car and it didn't misfire at all
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