Okay so first it's an 07 ss/sc and I'm throwing a p0301 which is misfire cyl no.1 and that's it the lash adjusters are fine I switched injector 1 and 2 and the misfire stayed in cyl no. 1 I also changed the plugs and gapped them and switched coil packs and still nothing and the symptoms occur sometimes and when they do my car idles like crap and sounds like a subie please help I'm about to roll it off a cliff

 

go do a leak down test and a compression test sounds liek you may have popped a piston

 

are you tuned in any way? my car does this sometimes on startup, gets a rough idle and sets a p0300. ive made a couple tuning tweaks and its gotten less frequent, but still there at times.

sounds like you have covered the electronic side of things. as mentioned, compression and/or leakdown test. if that looks ok, you may have a cracked intake or something causing a vacuum leak into #1 cylinder.

 

I hope not! ill do a compression test tonight..but could that cause it to come and go? I figured it would be all the time if I had low compression

 

Sharkey I don't have any tune or Any major upgrades for that matter but not a bad idea I'll check for a cracked intake many

 

i doubt its a cracked intake manifold

 

Did the compression test last night it checked out fine now I just need to do a leak down. It ran fine all yesterday and this morning but when I got to work the subie mod came back and it idled like crap.

 

Apperently everything seems good that youve checked all the normal stuff so far.
Other things that can cause P0301 that you may could check

1: Wire harness to the #1 Coil Pack. A Damaged wire can prevent a good coil pack from fireing the plug
2: Wire harness to #1 Fuel Injector. A Damaged wire can prevent a good fuel injector from injecting fuel

 

when checking the injector and the coild pack for a short should i just check the ones leading to cyl no. 1 or check the whole harness? when its dark im gonna start the car in the garage and turn the lights off and see if i see any random sparks going on too

 

do a leak down test

 

I will the problem is I don't have a tester and don't have money for one right now...balling on a budget haha

 

alright so i checked the wiring and found like 5 different spots of exposed wire running to the no. 1 injector they are very small looks like a mouse had a field day on it so lets hope this is the problem ill let you know

 

Dont just check for shorts, check for conductivity from the injector/coil pack plug, to the other end of the wire.
Looks like you found what was probably causeign your problem. A Dark check may not work well since the voltage is only 12VDC and is stepped up by the coil packs.....

Your cheapest and eaysest way to repair is to wrap those wires in electrical tap. If the problem goes away that was your issue. Though the best repair would be to replace the entire harness.

 

you dont need to replace the entire harness, just repair it. remove the injector harness, cut out the damaged section of wire and solder in a new one, and complete the repair with heat shrink tube.

 

did exactly what sharkey said had my dad (who is an electrical engineer) repair it by soldering it and putting shrink tube on and the i wrapped it with electrical tape...not the problem im gonna do a spark test with number 1 coil pack and if that doesnt work im gonna nut up and take it to the shop and have them take off the cylinder head...i had the head redone professionally and put back together by them like 15k miles ago if there is a bent valve or its not seating properly better believe this will be a free fix by them..thanks for all the help guys will keep you posted with info for sure...feel free to leave more suggestions before i break my bank lol

 

If your dad's an electrical engineer im sure he looked at the rest of the harness too. Have him help you check the wire harness to the Coil Pack. Im not sure what a spark test will tell you that you dont already know. If there is sparks flying out of one of the coil packs, your P301 would have swapped to a diffrent cyldinder when you swapped coil packs. How did your sparkplugs look when you removed them?


When you did your compression test what were your numbers?

 

#1 and #3 were 145 and #2 and #4 are 155 i was gonna try a spark test when it was running rough to see if the harness has a short im in the process of checking that now....random question dont want to get off topic but where does the ground strap on the top of your valve cover connect to? both ends would be helpful.

 

well you found your problem 145 and 155 either you got a **** valve job or it needs a set of rings put in im gonna say rings stock compression is supposed to 190 to 220

the ground strap connects to the center post in the valve cover and to a bolt hole on the head right below the top bolt

 

it was just a harbor freight compression tester could have been a s*** gauge thats a big difference lol but id have problems a all cylinders if i was that low so im leading to belive was a crappy compression tester ill try a new one today and see what numbers come up

 

my harbor freight comp tester works just fine and no you wouldent have problems in all four cylinders i did a lsj that had 150 across the board and missfired bad in #3

 

ill pull them out in a sec but could you answer my ground strap question real quick?

 

i pulled plugs 1 through 4 and they all look the same slight carbon build up nothing out of the ordinary no oil or gas on them or coolant.

 

i did answer that question

the ground strap connects to the center post in the valve cover and to a bolt hole on the head right below the top bolt

carbon will cause missfires

 

oooh my bad man i didnt see that but that is not where the ground is connected on my car lol not even close i will be checking this asap ill clean the plugs too and see if anything changes

 

the ground was not connected to the head at all...dont ask me why but i fixed it and it is purring like a kitten i erased the codes so ill let you know if it pops back up also after all this i wanna clean with seafoam good idea? or not necessary?