jants13

2005 A6, 4.2L, BNK Engine.

So I changed my air filter and fuel filter over the weekend. All went seemingly well, and I was able to drive the car for a 3 mile test drive and back home from my parents house (5 miles) on Saturday without any issues.

Sunday, I went to start the car and noticed my check engine light was on, but it ran fine. I thought maybe I missed that on my drive home as it's directly behind the steering wheel where I hold my hand, and maybe it was caused by pulling the fuel pump fuse and running the car to get the pressure out of the system for the filter change, so I cleared the codes. Started it back up and in ran fine at first. Pulled out of the drive way and within 100 yards the check engine light was back and blinking this time. The car also started to misfire and run really rough. Kicked the wife and kids out of the car, told them to walk back home and limped the car back home.

Pulled the codes - P0300 and P0308. Random/Multiple cylinder misfire and cylinder 8 misfire. And finally C342D - Manufacturer Control code. From what I can tell, this last code is bogus as I can't find a meaning for that. And clearing the codes and starting the car will trip the same codes again, although like 8 of them in total, duplicates of the 3.

At first I thought maybe Napa gave me the wrong fuel filter that didn't put as much fuel through as it needed and put the old one back on. Same deal.

I also pulled the air filter and double checked that one plug and the vacuum hoses behind the air filter housing. All looked well.

The only other thing to note is that when taking the first part of the intake off to get to the air filter, I also accidentally pried open the other end of the plastic intake tube that attaches to the engine. I did reattach that though and didn't see anything else loose over there.

At this point I'm out of ideas and don't know what else to check. The car runs really rough and blinks the CEL.. I may also have access to a VagCom cable, but it's a bit of an undertaking..

Thoughts?

Thanks,
- Jan

raj99

sounds like you might have an leak in one of your hoses somewhere...As for the misfire, did you try to change out the coil packs and see if the coil pack is perhaps the issue?

jants13

Have not swapped out the coil packs yet, but while I know correlation is not causation, I'm still leaning towards me knocking something loose while working on other stuff or somehow causing something to fail due to lack of fuel in the system..

And the coil packs were semi-freshly replaced as part of the recall maybe a year or so ago..

Will look for leaky hoses in the intake area though..

newa6er

Look at the Mass Air flow sensor connections, were you wear rubber gloves?

jants13

Didn't touch the sensor itself, but no, no gloves.

haloguy628

Get electronic cleaner spray and clean all the connections on the airbox and on the coils.

If it persists switch the #8 coil with say #4 coil and see if the misfire will show on the #4 cylinder. If yes then you have bad coil.

If the problem persists then clean the MAF sensor with electronic cleaner gently using clean Q-tip soaked in the cleaning fluid.

I don't think that you have vacuum leak as you would get one of the "bank #X running lean" codes and not a misfire code.

jants13

So a few more details..

Swapped cylinder 8 coil with cylinder 6. Still the same cylinder 8 error along with the multiple/random error.. not the coil.

Tried looking for vacuum leaks by listening and blowing smoke into the intake area looking for disturbances. Didn't find anything obvious.


Then I noticed something odd - the passenger side exhaust is warm, whereas the driver side is completely cold, meaning no combustion on that entire bank. Also, pulled the number 8 spark-plug when I swapped the coils and it was wet with gas.


Now, it's pretty obvious I'm not getting combustion on that whole bank. One misfiring cylinder would not sound that bad on a v8 engine, plus if any part of that bank was firing at all, the exhaust would be warm. Now the question is why is there no combustion. Air, fuel, spark, and timing of the spark are the needed components:
Air - air is distributed to both banks equally, right?
Fuel - there is one entry point into the fuel rail. Though in theory changing the fuel filter could have gotten some gunk into the rail that just happened to go into that side of the rail and could have clogged the rail or some of the injectors on that side. The #8 spark plug was wet though...
Spark - How do I check if I'm getting spark if there is no exposed coil wires to attach a timing gun to, or no exposed spark plug to attach one of those pass-through lights to?
Timing - without a distributor, what tells the plugs to fire? Is that a cam sensor of some kind?

Also, I suppose the worse case scenario would be something mechanical on that bank.. how and what would I check for with that? There's no mechanical clunking sounds, only the sounds of air in cylinders getting compressed.


Also borrowed a buddy's VagCom cable but were not able to get any concise code off of it because the battery was dying by the time I got to that. At this point pretty much everything it pulled had to do with a low battery. Put the battery on a trickle charger and will try again tomorrrow.

Thanks,
- Jan

EDIT: After some more research, I think the next thing to check is the cam solenoid valves as noted here: https://www.audiworld.com/forums/a6-...et-al-2866519/
Now I just need to figure out where these puppies are located..

jants13

So the cam solenoids click if I run the test in VCDS. Can I assume those are good?

Can anyone tell me where the cam sensor is on the 4.2L for the 2nd bank?

Also, anyone have any brilliant ideas fow how to check for spark on these cars? Normally I'd just attach a timing gun to a plug wire..

Is there an easy way with a vagcom cable to check the cam sensor or cam chain guides?

Thanks,
J

jants13

For what it's worth, it's the chain guides for the second bank that are bad. Don't know about the valves. Haven't checked the compression.

Got an estimate from the dealer though to fix for TEN THOUSAND and something dollars. I stopped listening after the ten thousand.. and that's American dollars! They won't give me an itemized list of parts and labor either... Still calling around indy shops though for a more reasonable offer, but haven't found anyone that has ever done a 4.2.

Or the dealers also offered a used engine swap for $3500 for an engine plus ~$3000+ labor.

Anyone in the pacific northwest want to buy an 05 A6 4.2L with sports suspension, 150k on the clock and broken chain guides? It's probably time for a new car at this point..

raj99

Sorry to hear the bad news. This is exactly what happened to Kevin's 05 4.2 and well as you are aware, it's not a cheap repair. If I were looking for a project car, I'd be calling you up