so this started about a month ago, and i've just kinda dealt with it..

Originally it was only on COLD starts it would miss for a few seconds (the CEL would flash) and everything would be peachy for the rest of the trip. The code that was displaying was P0305 Misfire on #5 cylinder. At that point i swapped the spark plug, coil, and fuel injector with cylinder #4 and erased the codes. the problem continued (hopefully on cylinder 4 now), but when i had the codes read it showed cylinder 5 again.

I figured it was probably a sticky lifter or something, so i ran a oil treatment, with no change.

Today i had was checking the codes to see if anything else had cropped up, and i have 7 codes in total, but the misfire ones are what im really worried about.

P0305 - misfire on cylinder 5
P0304 - misfire on cylinder 4
P0300 - multipal random misfire

P0155 o2 sensor B2S1
P0421 Cat below efficiency B1
P0491 secondary air injection
P0492 secondary air injection

any ideas on what could be causing the misfire codes? - The 2 specific cylinders are obviously on the same bank.. i've had a all the plugs changed this year, and i've had all the coils changed in the last 3 years..

PS: Its due for a timing belt, not sure if that could have something to do with it..

Thanks in advance
-Josh

 

As I posted this question several times with probably 1000 views and not a single reply.. Not to mention reading all the other posts I could with no resolve I thought I'd get back on here and post the resolution.

It turns out that it was a very small coolant leak into the cylinder as I figured it was. Instead of spending thousands on gaskets and labor to (hopefully) fix it by preforming a top end rebuild I opted for a coolant based head gasket treatment.. Bars head gasket sealant with block seal $35 at AutoZone.. Followed the directions on the bottle and it sealed the first run.. No more miss..

Now I know what your thinking because I was thinking the same.. "Cheap" "lazy" "wrong".. But as the car has 192k miles on it its simply not worth a $3000 rebuild (if I did the work myself)..

Its your choice, but if your having a cold start miss and its not your fuel injector, spark plug, or coil.. Its probably your head gasket.. And its not always just a "parts replacement" as your head or block might even need machine work..

Best of luck to anyone who has this issue
-Josh

 

i have same issue. i pulled spark plug and looked in the cylinder. it looks like oil on the piston i think. after it stops misfiring, the idle returns normal and no longer smokes. if i rev the engine a little, it seems to make the misfire stop earlier.
im thinking my issue is valve stem seal.

 

Yes, it could be oil valve stems too.. If you pull the plug you can stick a pipe cleaner down there and play with it in your fingers to find out what it is.. You might see blue smoke or smell oil in the exhaust too..

 

yes i smell and see smoke. this only happens on startup during the misfires. the smoke usually disappears when the misfire settles.

i was reading up and a possibility could be the suction pump failed in the pcv system? I'm experiencing issues that would relate to that such as the misfire, and oil leaking into combustion chamber, so far had to replace 2 vacuum lines twice due to them bursting which i think is because of pressure from either under boost or crank case pressure.

 

I didn't know you had a turbo.. Mine is a v6..

I don't think PVC would cause a cold start misfire..

Blowing vac lines isn't uncommon as they get brittle.. But if you think its abnormal you might have a failed check valve..

Do you know if its just 1 cylinder? Get the codes read AND cleared at AutoZone.. Then go back a day or 2 later and get the codes read again..

If its the same cylinder and it is in fact oil its likely a oil stem seal or head gasket.. You can do a compression test to diagnose between the two..

If it isn't the same cylinder the usual culprit is a leaking turbo.. It could possibly be a vac line related (but I kinda doubt it)

Let me know..

 

i have vag com and yes cyl 2 is always constant. i swapped plugs and coil packs and code comes back "random misfire and cyl 2 misfire"

i did a compression check last week and they all were with in spec with each other(I.E. the variation was ~10% or less) except cyl 2. it was 185-205-190-185. so i suspect cyl 2 to be higher because oil in the chamber.

only thing i can think of with the pcv system causing a misfire is if there was a leak causing unmetered air to enter.

i think im going to try a leakdown test this weekend but i also thing like you say it may be the valve stem seal

 

I agree on the unmetered air, but that would cause lean/rich fuel mixtures all the time.. Your car would always be a little sluggish/sputtery.. It wouldn't be just at cold start..

Plus it wouldn't cause oil in the cylinder at startup because once you lose vacuum (engine shut off) nothing can even get into/through the vac lines..

This is caused by a seal that has oil resting on it that is leaking just enough that you don't notice it when its running, however, when you shut the engine off it continues to leak a small amount of oil into the intake.

 

found my issue... the headgasket is leaking. i pulled spark plugs after driving it and cylinder 2 had a hissing sound. when i released the pressure from the coolant expansion tank the hissing stops.

 

I have an A4 3.0 with a CEL reading of cylinder 6 misfire. Not sure what to do. I hope someone one this forum can help! The dealership suggested I have it towed in for repair .... I don't think so. It only has 78k miles, so hopefully the coils, or spark plugs - I have no idea, I've never dealt with fixing vehicles as most of mine were new and under warranty. This was used, but is sooo expensive Any advice would be appreciated!!