odoboyusa

Hello everyone!
I have been trying to help a friend with a 03 A6 3.0 AVK automatic.
He replaced the engine.
The car always starts, sometimes takes a couple cranks, sometimes one or two. When pressing the accelerator, the engine sometimes revs up to 3k and then slowly starts coming down to the point of stalling. Very rarely it will stay running for more than 30 sec. Mostly even at idle it will end up gradually slowing down and stalling.
I confirmed the throttle plate works by checking vacuum in the manifold.
Checked fuel pressure while running: 50-55psi
Quadruple checked timing: Used the cam locking tools, crank lock pin and the tool to clock the exhaust tensioners. I pulled all the cam sensors and physically verified the position of the rotors for the cam sensors. Confirmed I could see one of the two lines in the middle of the hole. On the intake shafts it was the line on the high point on the rotor and on the exhaust it was the line on the low point.
With vcds I checked block 90, 91 and 92. Intake cam adjuster are 0 for requested and actual. exhaust though are 0 for requested but 17 and 25 for actual.
I am now wondering if it's not an oil pressure issue where the exhaust cam adjusters are stuck in the completely advanced position and if they need oil pressure to unlock (i know on the c6 that's the case). With the timing belt off and cam bolts still tight, i could only turn the timing belt pulley very little.
I was also thinking about the crankshaft position sensor maybe being problematic...

So other than the CPS and oil pressure, I'm out of ideas and pretty baffled.
Any pointers would be gladly appreciated and beer will be sent your way

Here's the reading from vcds as far as codes.
What does implausible signal really mean? Bad electrical signal like a weak wave or just confusing signal where the transitions are not when expected?


Address 01: Engine Labels: 06C-909-559-ASN.lbl
Control Module Part Number: 8E0 909 559 E HW: 8E0 909 059
Component and/or Version: 3.0L V6/5V G04 0004
Software Coding: 0016752
Work Shop Code: WSC 03323 444 52476
VCID: 377D9EDD452451A0D06

16775 - Camshaft Position Sensor (G301)
P0391 - 004 - Implausible Signal - MIL ON
16750 - Camshaft Position Sensor B Bank 1 (G300)
P0366 - 004 - Implausible Signal - MIL ON
17755 - Camshaft Position Sensor 2 (G163) / Engine Speed Sensor (G28)
P1347 - 001 - Incor. Correl. - MIL ON
17748 - Camshaft Position Sensor (G40) / Engine Speed Sensor (G28)
P1340 - 001 - Incor. Correlation - MIL ON

GTA_Driver

Your timing is most certainly off. I have never set the timing on these cars myself, so i am not an expert, but i have experience with these codes personally and many others on the forum.

Any time you have a code for correlation being incorrect, it's timing.

Something in your procedure is amiss.

How many links in the chain did you count on each bank?

odoboyusa

Thanks for chiming in!
That was exactly what I said initially: cams and crankshaft are offset by a certain number of degrees so it must be timing.
This engine does not have the chains between the intake and exhaust cams. I wish this was a 2.7 or 2.8, i know those much better.

on this engine the timing belt drives both the intake and exhaust shafts and there are hydraulic adjusters on both intake and exhaust, in the pulleys. Oil comes through the camshafts.

Forgot to say I did a compression test: got between 165 and 175 psi on all cylinders.

I followed the bentley procedure for the timing belt with all the appropriate tools, even the one for the eccentric roller bearing. At the end of the procedure, before tightening all cam pulley bolts, the exhaust tensioner gets rotated clockwise until it stops. In my case it was already there.

If the timing was off, wouldn't compression be affected?

Also, the owner of the car has adjusters from the engine he pulled and we swapped those with no difference.

Metronet

I had a similar issue with my AVK where it would not idle properly. The codes I got are different than yours and so perhaps just use this as a reference. I was getting DTC P0025 (16409 B Camshaft Position, Bank 1 - Timing over-retarded) and was still with the older version "D" software (I see that you are already on the latest 8E0 909 559 E/004).

After flashing the software using VAS-PC it helped but still misfires were stubborn at that time. The problem was with bank1 but somehow it affected cylinders in the other bank as well. It turned out to be the camshaft adjuster had came loose on it's own!

See attached TSB for more details... it's all documented there about this particular issue on the 3.0

Let us know how it goes with your troubleshooting and... Good luck!

4Driver4

Did he use the tools when he installed the new belt? I agree with the others that the timing is off.

Has he done a TBA?

odoboyusa

We used all the audi tools in the instructions. Cam locks, crank lock pin, adjuster clocking tool, eccentric bearing turning tool.
Also the marks on the crankshaft ends were in the proper place when looking through the CPS port.
We always spun the engine by hand after doing timing to double check.
Also, the engine doesn't run rough.
TB adaptation was done with no issue.

For example if I held my foot on the accelerator to the floor, the engine would rev up to 3-4k and then gradually slow down to the point of stalling. as it's getting below 2k rpm I also hear some backfires in the intake, random not rhythmic. But sometimes the engine would run and idle considerably more (even 60 seconds) sometimes it would stall in less than 10 secs.

My guess is this: the exhaust adjusters are clocked/advanced manually (clockwise) to max when doing timing and they lock in place. They need oil pressure to unlock and go back to 0. Tried to move the adjuster back and forth when the belt was off and could not. I noticed the adjusters range is -4 to +25 or something like that. I'm guessing we're looking at an oil pressure issue. Too low oil pressure would cause problems with the adjusters since they're oil pressure driven. I'm also thinking the engine slowdown might have to do with friction but if things would be that bad, compression would be affected. The way the engine slows down is exactly like it would run out of gas, flooring the gas does not affect output noise but i can see vacuum is gone so the throttle is open.
Could a bad crank position sensor cause these issues?

Thanks a lot for the advice! I know this is a mind bender...

jcman

Too low of oil pressure would throw a red indicator symbol, a bad crank sensor either has a code running or will not start at all.

The cam adjuster is electronic also.

odoboyusa

I thought so too but as far as i know, the oil pressure light has a couple psi threshold so it will only show up when there is no oil pressure. I know there is some because the engine is not ticking and there is oil in the heads.
The solenoids are electrical but they work on oil pressure to control the adjusters, to actually push some vanes inside.

You're right about the crank sensor, that's what i was thinking too... I'm just running out of ideas.

odoboyusa

So I figured i should come back with results, the engine is working
Unfortunately my friend did several things and not sure which exact one fixed the issue. Maybe a combination.
- he replaced a defective vacuum check valve - air would flow both ways
- he pulled the oil pan and cleaned a little bit of dirt from the oil sump screen
- he replaced a sealing ring (like a piston ring) that is mounted on the camshaft end, to allow oil to flow from the head to the camshaft then through the camshaft to the adjuster. There are two channels sealed by 3 rings.

He also checked the adjusters by taking them apart. Both exhaust camshafts have a locking pin in the most forward (i guess advanced) position. Oil pressure is needed to unlock these and let them fall back. Not enough oil pressure, no unlock...

Thanks for all the help and ideas!

Metronet

That is fantastic! I am glad you figured it out and all is well.