Unfortunately I never got the opertunity to play bad cop......and my friend who's less than automotive savvy got taken on an A6 that was neglected and sold on the vehicle being "mint" physically. It made it home and sat for two months after his 10 mile drive after purchase before he let me know what he bought or that it hasn't driven since the day he drove it home.
05 A6 4.2 Quattro 160k. Valve covers leaking enough to merit a visit from Greenpeace, lots of engine noise, clear miss fires, dead battery, broken cam tensioner pad.......
I got it started after a little love with a new battery and some simple checks. After initial inspection and some minor maintenance it was driveable but it still wasnt to standard. I treated it to valve cover gaskets, crankshaft moons, a new driver side valve cover(cracked), oil change, filter, new coils, new plugs, crank position sensors....Upon removing the covers I found the typical broken pad on the left driverside tensioner but was elated to discover that the cams, and lobes looked great. I found numerous broken vacum lines (fixed) and a broken wire on the passenger side crank sensor (re pinned and soldered) I also found it had new timing chain's (factory) and was certain that after replacing the cracked pad I was in the clear........Woe is me.......
As my friend is semi disabled I have tried to get his less than practical relatively clean physically A6 ruinning so it's not merely a driveway decoration. I didn't replace the tensioner just the pad and the coils and sensors are Duralast. Upon installing and fixing all of the above mentioned I have little to no change........ Although it runs and moves, it is far from sea worthy. I no longer have engine chatter or oil leaks, but the miss fires are beyond tolerable. I don't have a vagcom but am still getting the following codes on the constantly flashing Christmas tree: P0 300, 340 343, 345 crank shaft position failure, multiple cylinder misfires, P0106 barometric pressure no Bueno, and I noticed the passenger side cat behind bank 1-4 is so bright orange you could cook off of it. I didn't verify that the timing was correct initially but am certain that I marked the driver rear chain precisely when I loosened the tensioner to replace the pad. ( I verified that my marks prior are spot on. I ordered the cam lock bar and intend to pull the front clip and verify the timing. I'not Im not opposed to changing the tensioner but was thrown off by the ones I find online appearing different from the ones in this vehicle. The pads are north south with the solenoid pointing east west out of the back of the valve cover.. the ones I see online also have a connector off of said solenoid (not a pigtail) and both the solenoid and pads face the same way? As the owner of this car is a veteran and on limited income, I'm trying to help him to the best of my ability.
Initially the vehicle had a cracked valve cover, leaky gaskets, a broken upper tensioner pad, a hole in the breather, fouled plugs.....it was sluggish but relatively smooth, and the missfires were present but not nightmarish.
Although the cracked valve cover made me think that the ttensioner failed sending the chain through it, my thoughts were that it not possible for the tight chain to have skipped several inches busting the valve cover only to magically reappear on the sprockets timed well enough for the vehicle to drive. If the timing was off a tooth or 3, that the symptoms would be far worse than a few missfires. As the other pads look new, and the broken one looked quite warn, I thought perhaps said pad had perhaps been inadvertently not replaced with the evident chain work. The vehicle now starts much better, there is no more grinding noise of the broken pad flopping around, but the miss fires are still present. If the valves were bent , or timing off, would the vehicle even start or drive? I drew a strait line down chain, and tensioner gear and said line is dead strait inline. Any insight will be greatly appreciated.

 

Run a compression check on all the cylinders. You may have a slightly bent valve on the exhaust side.

 

Thank you Dave, I will start there and report back.

 

I openly admit my new found love hate relationship with this 05 A6 C6 4.2L. This high milage car (160k) has actually had extensive maintenence including a new block and timing chain's @150k. Vehicle has hesitation at initial acceleration but smoothes out around 2.2k rpms. Idle sits around .8k with slight hesitation roughly the equivalent of the width of the needle. P0300 generic missfire, 0340, 0343, 0345 Cam Position sensor A circuit High. 0305, 0306 cylinder missfires. Compression is good!

I have repaired all of the oil leaks: valve cover, crank, and oil pan. New vaccum lines.
It has new coils, new ngk plugs gapped correctly, a new oil cooler, o rings, return pipe and o rings, both cam position sensors, maf sensor, fresh 05w40 oil and audi coolant with a new filter.

I just ordered a fuel filter, and a pvc valve.

If someone could answer the following I would be MOST APPRECIATIVE!

Can the timing be verified without removing the engine? Can I verify the timing on the drivers rear upper cam chain without removing the engine? The diagram I have appears to be incorrect. I am guessing for a c5? Unless I'm blind and simply don't see any triangle or square on the sprocket.

When I first got the car it had dreaded chain rattle. I removed the broken driver side rear tensioner pad (mostly intact) and replaced it. I was extremely precise in making sure the chain/cam did not rotate from original position. The chain is very snug.

If timing did indeed skip 1 tooth for say when this pad gave way, would the car fire up on a dime and run so smoothly under pressure?

Lastly, if the hydraulic tensioner is bad, must I remove the engine or can I remove the cam caps and cam and replace just the tensioner? I have pulsed the tensioner and it does click like a relay, but I fear it might be bad based on what I have read.

I am not too lazy to pull the motor, it's just so frustrating that the car seems so close to beING correct (like 1/2 or 1 tooth) and there seems to be so much conflicting info between c5 4.2L and an 05 c6 4.2. I am in awe of having to tear the motor out just to verify the timing. If this car hadn't had ridiculous money spent under the hood (block, chains) semi recently, I would dread the labor as it seems I'll advised not to overhaul if pulling. The milage makes the car not economically viable to do so.........And I will be really pissed If I pull the motor needlessly.

I am MOST GRATEFUL FOR ANY INSIGHT!

 

hi,
so sorry to hear that. did you solve the problem yet? i think it the the cylinders damaged.
best wishes to you.

 

If the cylinders were damaged, I wouldn't think that the motor would run perfectly above 2.5 rpms?

 

You do not have to pull the engine to do those things. Simply moving the front fascia and radiator support forward to the "service" position allows you change out and check all that stuff without pulling the engine. It seems to me that it's possible that one of the cam gears is slightly off. These things are not keyed on the cams, instead they ride on a tapered surface and are locked into place by the bolts that old them on. You must have the cam timing marks lined up with the marks on the head (under the valve covers on the cam caps) and the crank must be locked with a lock pin inserted in the block to make sure those are correctly timed before tensioning and locking down the timing gears on the cams. You really need to get the crank lock pin and cam gear locking bar in order to do it right. I'd also pick up the cam gear puller because a normal gear puller will not be able to grab the cam gears with them installed in the head. The cam gears need to be unseated (and let me tell you, when they're tightened down, they are NOT going anywhere easily) in order to set them. There are a couple or three videos on Youtube that show the basics behind setting the timing on these things. If you don't get it perfect, it will not run properly. Get it way off and it will bend valves. Obviously this is not the case here. So it appears that one of the cams may be just a degree or so off. It just needs to be reset.