Engine fault code P0303 Cylinder 3 Misfire, can it be my PCV?

[crlsjcb05]

As title says, I'm getting the check engine light with that code. I've replaced the spark plugs and coil packs on my car once I saw the code. Worked alright, but the code returned, so I fueled up and added some Lucas injector cleaner. Again, no big change. I found this thread on a semi-related issue:


"I have a misfiring issue the fault code is p0301"

and he later states

"Turn out my PCV breather hose is leaking."

http://www.audiforums.com/forum/b7-m...-166720/page2/


So I look up PCV leak and..


"I read that the PCV valve can go bad and the way to tell is to pull the oil filler cap while the car is running. If it runs rough and/or has suction, then the PCV is going bad."

"Yes - my oil cap was stuck on tight when I had the PCV problem. Could also hear a hissing sound right after I shut the engine off and there was a DTC code (though no CEL). Replacement PCV, under warranty, removed all those symptoms."

http://forums.audiworld.com/showthread.php?t=2809353


I did the oil filler cap test and sure enough, cap is on tight, once i take it off, suction occurs and engine is idling very rough. Might these issues be related, or do I have two separate problems on my hand?

[dhinez]

How many miles on the car?
What is you car doing on cold starts?
Does it mis-fire the entire time the car is running or does only do it for the first couple of minutes then runs fine?

I have a 2007 Audi A3 with Stage 2+. I had this issue too but instead I was was throwing P0301 and P0302. My issue consisted of rough idle on cold starts due to the misfires then it would smooth out after a minute or so and drive fine until the next cold start. I've done new spark plugs, new coil packs, new cam follower, and boost leak test. I have the BSH PCV bypass plate which eliminates the PCV valve as an issue. Even with all these fixes I was getting CEL with the same codes being thrown. I finally took the dive and did an intake valve cleaning last night. I was surprised how bad my valves were clogged on cylinders 1 and 2. There was so much carbon and sludge buildup. When you do this, I would recommend new gaskets such as intake manifold gasket and fuel injector gasket kits. I'm not saying that your problem may be as severe as mines. Since I was in there, I also did the runner flap delete. My car has 86,000 miles.

Hopefully you can get away with not spending too much money on fixing the problem. I would recommend that you change your PCV valve and maybe do a boost leak test for vacuum leaks since that would be the cheapest thing to do. Good Luck.

[Badger137]

The pcv can be change under extended waranty at the dealer (do on my 2006 a3)if you have change the 4 plugs and coils ,and the pcv,it can be the carbon build on the intake valve.

[crlsjcb05]

How many miles on the car?
What is you car doing on cold starts?
Does it mis-fire the entire time the car is running or does only do it for the first couple of minutes then runs fine?

I have a 2007 Audi A3 with Stage 2+. I had this issue too but instead I was was throwing P0301 and P0302. My issue consisted of rough idle on cold starts due to the misfires then it would smooth out after a minute or so and drive fine until the next cold start. I've done new spark plugs, new coil packs, new cam follower, and boost leak test. I have the BSH PCV bypass plate which eliminates the PCV valve as an issue. Even with all these fixes I was getting CEL with the same codes being thrown. I finally took the dive and did an intake valve cleaning last night. I was surprised how bad my valves were clogged on cylinders 1 and 2. There was so much carbon and sludge buildup. When you do this, I would recommend new gaskets such as intake manifold gasket and fuel injector gasket kits. I'm not saying that your problem may be as severe as mines. Since I was in there, I also did the runner flap delete. My car has 86,000 miles.

Hopefully you can get away with not spending too much money on fixing the problem. I would recommend that you change your PCV valve and maybe do a boost leak test for vacuum leaks since that would be the cheapest thing to do. Good Luck.

130K. Unfortunatelly, I believe the warranty may have expired for me.

It starts normally, once the warm up slows down (goes back to idle) there is a little shake that comes and goes from day to day. But as soon as it hits the idle RPM (around 800 RPM or what have you) the shaking stops and them drives fine.

I have also been reading alot of that carbon build up. Was it too much work to take the head off?

[Badger137]

You don't have to remove the head, only remove the intake .check whit your dealer because the pcv was onder extended warranty on my 2006 a3 whit 133k km.

[dhinez]

130K. Unfortunatelly, I believe the warranty may have expired for me.

It starts normally, once the warm up slows down (goes back to idle) there is a little shake that comes and goes from day to day. But as soon as it hits the idle RPM (around 800 RPM or what have you) the shaking stops and them drives fine.

I have also been reading alot of that carbon build up. Was it too much work to take the head off?

Like crlsjcb05 said, you don't have to take the head off just the actually intake manifold. Here is the DIY I used when I did mines: http://www.golfmkv.com/forums/showthread.php?t=140523. You don't have to take your front clip off like the guy in the thread does. It's very thorough. On my car I found a hidden bolt that was not covered by any of the DIY cleaning threads. I'll post a pic of the location later. It's been almost two weeks since the cleaning and I haven't had a CEL come on.

[crlsjcb05]

You don't have to remove the head, only remove the intake .check whit your dealer because the pcv was onder extended warranty on my 2006 a3 whit 133k km.

Thanks! I'm going to contact my local dealreship (Monterey CA) and see if I can get that checked out

Like crlsjcb05 said, you don't have to take the head off just the actually intake manifold. Here is the DIY I used when I did mines: http://www.golfmkv.com/forums/showthread.php?t=140523. You don't have to take your front clip off like the guy in the thread does. It's very thorough. On my car I found a hidden bolt that was not covered by any of the DIY cleaning threads. I'll post a pic of the location later. It's been almost two weeks since the cleaning and I haven't had a CEL come on.

Cool! Thanks for the link! I'm thinking of doing when for the next time I'm up for a major maintenece (water pump / timing belt service)

All I'm wondering now is if maybe it's thr injector that might be causing that missfire...

[yepodm]

As title says, I'm getting the check engine light with that code. I've replaced the spark plugs and coil packs on my car once I saw the code. Worked alright, but the code returned, so I fueled up and added some Lucas injector cleaner. Again, no big change. I found this thread on a semi-related issue:


"I have a misfiring issue the fault code is p0301"

and he later states

"Turn out my PCV breather hose is leaking."

http://www.audiforums.com/forum/b7-m...-166720/page2/


So I look up PCV leak and..


"I read that the PCV valve can go bad and the way to tell is to pull the oil filler cap while the car is running. If it runs rough and/or has suction, then the PCV is going bad."

"Yes - my oil cap was stuck on tight when I had the PCV problem. Could also hear a hissing sound right after I shut the engine off and there was a DTC code (though no CEL). Replacement PCV, under warranty, removed all those symptoms."

http://forums.audiworld.com/showthread.php?t=2809353


I did the oil filler cap test and sure enough, cap is on tight, once i take it off, suction occurs and engine is idling very rough. Might these issues be related, or do I have two separate problems on my hand?

Have you been able to resolve the problem of misfire in cylinder #3? I have the same problem.