mc_hotmail

Replaced drive belt, timing belt, water pump, thermostat, all cam and head cover seals. Had to re-fit the cam timing chain, but before closing up, all 4 cam position markers were aligned.

This '04 allroad 2.7T BEL started, idled and ran fine the first time after the job but did not feel the low end torque expected of this engine. The code was P0348. Found the cam position senor 2 was not plugged in.

P0341 Camshaft Position Sensor Circuit Range/Performance
P0345 Camshaft Position Sensor A Circuit Malfunction (Bank 2)
P0346 Camshaft Position Sensor A Circuit Range/Performance (Bank 2)
P0348 Camshaft Position Sensor A Circuit High Input (Bank 2)
P1347 Bank2,Crankshaft-/Camshaft os.Sens.Sign. Out of Sequence

Fixed that and got code P0346. I check the bank2 CPS connector: 1-3 is 5 volt, 2-3 is 12 volt, so they are good. Replaced bank 2 CPS with a new generic one and got P0341 and P0346. Put the original CPS back but swapped with the bank 1 CPS. Now I am getting P0346 and P0345. VAG-COM also logged P1347.

For previous cases in the forums, most folks suggested double check timing belt. So this morning, I removed both timing belt covers (broke a corner) and was able to fit the cam locking tool back on with ease. The TDC mark on the crankshaft (vibration damper) is only off to the right by 2mm (less than 1/8"). This is exactly what I had at the end of that whole job.

Questions for the pros:

1) With the cam lock tool and crankshaft TDC mark line up, does that clear the timing belt?

2) By swapping the CPS and the code remains in bank 2, that should clear both CPS. Then what else should I check?

One thing left to check seems to be wiring. Suggestions are appreciated.

Thanks

--mc

mc_hotmail

Answering my own question:

1) Able to put on the cam lock bar and the crankshaft TDC mark lining up does mean the timing belt was done correctly, but it does NOT necessarily mean the engine timing is correct.

The timing belt links the two cam sprockets with the crankshaft. However, 2.7t is a quad-cam engine. The sprockets are on the exhaust camshafts. The cam position sensor is on the intake camshaft, driven by the exhaust camshaft via the cam chain.

If the cam chain was fitted wrong by one teeth, the timing on the intake cam will be wrong, and the ECM will not get the right pulse from the CPS at the right time.

2) Swapping the 2 CPS proved they are both okay (the car was running before the job). The CPS connector 5 volt and 12 volt reading was enough for the Bently manual to rule out wiring problem.

I am leaning towards the worst case like this guy had:

http://www.audiforums.com/forum/audi...sensor-156937/

Plan to pop open the bank 2 valve cover while in TDC to confirm.

--mc

Prospeeder

ummm if its an 1/8 inch from the pointer on the crank obviously timing is way off. Thats your problem, put the crank EXACTLY on the mark, break the cam pulleys free, line up the cams with the bar, and retighten the cam bolts. Fixed.

mc_hotmail

I took Prospeeder's advice and did it 4 times, each selecting a different position for the TDC marker (a line on the vibration damper) relative to the TDC arrow on the timing belt cover plate. For each change (about 20 minutes), I only remove/install the 2 compressed air intake pipes, loosen/tighten the 2 cam sprockets. Idle fan is not installed but everything else (bumper, etc.) is in place.

Before the first attempt, the marker was 2mm to the right, I got P0346, P0345, P1347. This was the result when I first finished the whole job.

1) Set TDC marker dead on the arrow, I got P0346, P0345, P1347. Smooth idle.

2) Set TDC marker 3mm to the left of the arrow, I got P0345, P1347. Smooth idle.

3) Set TDC marker 6mm to the left of the arrow, I got P0345, P1347. Smooth idle.

4) Set TDC marker back to 3mm to the left (P0345, P1347). Test drive and the torque and response are a lot better than before.

P0345 and P1347 are basically the same code, one generic OBD2 code, and one Audi code. In VAG-COM, I only see P1347.

http://wiki.ross-tech.com/wiki/index...5/P1347/004935

That Ross-Tech page clear states that both timing belt and cam chain can lead to this code. It even says "Timing Chain probably lengthened", which match my original suspicion that I fitted the chain wrong by one extra teeth.

Looks like I must open the valve cover to verify. No time this weekend, will do it Monday.

mc_hotmail

Before I reopen the valve cover, I came up this idea to verify the TDC mark on the vibration damper of a 2.7t V6 engine. You can buy a similar USB snake cam (aka endoscope or borescope) for about $20. The camera head of mine is slightly bigger than the Audi spark plug thread, which is perfect.

I used a 15 inch breaker bar and a 15/16" socket (my substitute for the 24mm socket) to move the crankshaft near the TDC marker. Then while watching the computer screen, crank back and forth the TDC marker.

As shown in the attached picture, inserting the snake cam into the passenger side back cylinder (closest to the firewall) shows the cylinder is at top dead center, closest to the spark plug.

This also settles the argument of which is cylinder one. Inserting the snake cam into the passenger side front cylinder (closest to the radiator) shows that the cylinder is at bottom dead center, further away from the spark plug.

For my current problem, this confirms that the TDC marker on my vibration damper is correct. The damper has not slipped. The only possibility left is that I fitted the cam chain wrong.

mc_hotmail

The cam chain was off by one roller (see picture). It was a mistake to follow the Bently instruction about counting 16 rollers, because the chain is at an angle with the cam tensioner in place.

Since I took out the tensioner to clean its bottom surface, this time I fitted the chain flat. With the both cam markers (blue oval in the picture) on top, there should be 14 rollers between the 2 teeth above their respected cam markers.

Then I insert the tensioner and put the cams back. The exhaust marker is not aligned with the arrow, but I know I should trust the roller count instead of the arrow on bearing cap one.

Put everything back together, the timing is perfect, no code. My allroad is smooth and quick as before.

Some other take away for this job:

1) Vibration damper slipping is an exception, not the norm. The snakecam method confirms that.

2) The only accurate hint from any of the engine code is Ross-Tech's description for P1347, "Timing Chain probably lengthened". I had one extra chain roller between the exhaust and intake cam.

3) Swapping the cam position sensor is enough to verify that they were not the problem.

awdjunkies

Congrats on getting her back on the road.