Cyl 4 Misfire will NOT go away! (P0304)

[Custom Trendz Inc.]

I did the following:

Things I got/did after P0304:
MSD Coil
NGK Plugs Copper
New Wires
New front o2
CAI
UEL Headers
Stromung mid pipe w/ cherry bomb
Apexi WS2 catback
Swapped Injectors
Swapped Injector Plugs
New PCV
New fuel filter
SEAFOAM
Check for vacuum leaks with propane
reset the ecu(overnight method)
compression 168 on all cylinders(and yes the car also misfires when REAL cold as well as Operating Temp)
Batt checks out perfect(they didnt even try to sell me a batt like they usually do after testing)

someone please help i am at a loss.

[Huffer]

I would check your MSD coil and make sure your connections are solid there. Maybe try swapping in a NEW stock coil and see if the problem goes away.

You might consider looking at your cam and crank sensors too...they contribute to timing.

[Custom Trendz Inc.]

but cam sensors wouldnt just point at the 4th cylinder would it? and the crank sensor.

it misfired with stock coil, and is misfiring with the new coil. all those things were changed after the misfire started.

today it would vibrate violently(all the heatshields would make alllooooot of noise.) Im going to leak down test it tomorow, and compression test it again(maybe valve got fubar so thats why its worse.)

also, when i pull the plug wire off the coil(did not take the boot off(so it wouldnt start grounding) and the car didnt sound any different. So it could possibly be the coil, im going to check it with multimeter tomorow. I wish i could swap the plug wires while keeping them on the same coil terminal :/

[jey]

Might be an electrical issue - how's your gas mileage been?

[Custom Trendz Inc.]

mileage sucks real bad.

checked comrpession again after it started misfiring worse and i have cyl 4 at 115psi while others at 160. Leakdown shows 60% leak on cyl 4 and 30 on 2. Cyl 4 leaks into cyl 2, but not the other way around. Going to pull the head and see if its timing, valves, gasket, or a cracked head.

[ShadowGT]

Hmm.. seems like you're already on your way to finding out the culprit. I was going to say that I saw you added an UEL to your car. When I did that to mine, I got the same code. I loosened mine up, and torqued them back in. Reset the ECU, never saw that code again.

[Custom Trendz Inc.]

timing is not the issue, leakdown still shows same stuff going on. tomorow im going to check valve clearances, if 4 is by anyway really off i will get new shims and then leakdown test it again and if compression is fine just put it back together. And if thats not the case then the head is coming off.

im pretty much just going to leakdown the car at any step i do to make sure its fixed(only cyl4 is having problems)

[Custom Trendz Inc.]

leakdown after the cams came off proves same issue. So im taking the head off tomorow(only got the headbolts+exhaust bolts to take off and its off) then im going to take all the valves out(i know to keep them in order, snack bags work perfect for this!) Then ill either get new valve guides or valves if their burnt. I know its not bent valves, because in that case id have way too much spacing versus no spacing in the valves at all. Ill post tomorrow to let you guys know how it goes. Got to get this done by new years because i have to go to NH for friends 37 birthday and new years bash!

[Reason]

How are the piston rings and or the cylinder walls?

[Custom Trendz Inc.]

https://sl-i.net/FORUM/images/imported/2010/12/1222001248a-1.jpg
https://sl-i.net/FORUM/images/imported/2010/12/1222001248-1.jpg
https://sl-i.net/FORUM/images/imported/2010/12/1222001249-1.jpg
https://sl-i.net/FORUM/images/imported/2010/12/1222001249a-1.jpg

thats what i see.

proly replacing 4, 2, or none of the valves(depending how they are once i pull them out.) No place locally has shims or valves :/ so i might get used shims(a bunch) and some used valves.

[Custom Trendz Inc.]

https://sl-i.net/FORUM/images/imported/2010/12/1222001827-1.jpg

as you can see the tight exhaust valve is burned pretty bad(looks like someone bit it) so i will be replacing the 2 exhaust valves and reshimming the valves, and also reseating the valves.

[Reason]

Wow, I can see that could cause issues lol.

[Custom Trendz Inc.]

haha yeah it can. I got 2 used valves that had valve job done. So i rebuilt the head, reseated the valves, and then spaced them like the subaru mechanic(been around for 50 years, doing subarus for the last 20) and he said I can just grind the end off the valve. Did that and spaced them all to oem specs. Got new intake, header, and head gasket. Also got a timing belt and purolator filter just need to get some oil(castrol gtx high mileage.) Going to start putting it together, latest ill be done is sunday so ill let you all know.

[ouch1011]

How many miles on this engine? Its weird to see enough wear on the valve seats that it got that tight already.

You will want to check valve clearance on all the other valves as well.

[Custom Trendz Inc.]

i redid all valves to factory spec. car runs beautifully, from garage to 6-8 inches of snow :D