JSP242

I just bought my first Audi. It's a 2001 A6 Quattro with the 4.2L V8. It has 155k miles on the clock. I bought it really cheap from my boss, because he doesn't have time to fix it and sell it. It was his in-law's car for the past 6 years or so.


I'm just getting started on the digging into things and such. I bought a VAGcom adapter from amazon and just set up VCDS lite last night and plugged it in. Previously I had just plugged in with my standard OBD2 reader and checked the codes, and cleared them to see what would come back. So far the below code is the only thing that came back.



17755 - Camshaft Position Sensor 2 (G163) / Engine Speed Sensor (G28): Incor. Correl.
P1347 - 35-00 - -


From some reading it sounds like this could be a number of things. I'm looking for the most methodical way to check and test it out to figure out the issue and the fix. This certainly isn't the only issue I'm working through, but I think it's the most troubling one to have to deal with.


If anyone can help me get started on fixing this and learning Audi/VW that'd be greatly appreciated. Please post whatever from the Bentley for what I'd need to do if possible.


Also if I need to pull the timing apart, is there someone on here that I can borrow the correct timing locking tools from?


I assume the first step is to check the sensor. What pins do I need to check for which values and under which conditions?


I would guess the next step would be to check compression on the cylinders to try and make sure I don't have any bent valves.


Thanks Everyone
Cheers,
Josh

georgeb944

Not really the car to be learning on... If you screw it up, it could take a months salary to fix it.

That said... here's what the ross tech wiki says...

17755/P1347/004935 - Ross-Tech Wiki

JSP242

Thanks. I've come across that with all the searching I've been doing on this issue.

I'm not new to working on cars. This is my first Audi, and I've never really had to do engine work before. I bought it cheap enough that I figured I'd fix it and drive it for a while to see how I like it. If I like it I'll keep it, otherwise I should be able to sell it and not be out much.

JSP242

OK. So I finally had enough time at home to start digging into this. So I swapped the cam position sensors from bank to bank, and cleared the codes and ran the engine. The same code reappeared which indicates that there isn't a problem with the sensor. I then did a compression test. The driver side bank all read 240-250psi. The passenger side were 190-195 with one reading 215. So the driver side bank is obviously higher than I expected it to be, so based on that those results, I'd guess that there aren't any bent valves or anything otherwise compression wouldn't build up that high. So considering that I'm guessing that the valves are closing a bit early.

Next I did a quick visual check on the oval cam plates on the timing belt system. There isn't a good angle to really have a good visual of it, but it looks to me like they might be off a touch. So I think my next most logical step is to find the locking tools and check/redo the timing belt. Does anyone have the locking tools for doing the timing that I can borrow? Or does anyone know where I can get them. The one place I found that rents them requires you to buy their timing kit, and I'm not planning on purchasing a kit. I also don't want to spend the nearly $200 it would cost to buy the tools to use once for a car that I'm not likely to keep that long.

Thanks,
Josh

4Driver4

If you had bent valves, you'd be seeing misfire codes.

I think you are on the right track - resetting the belt timing is a good next step. I'll take a guess at a final diagnosis and say that one of the guides on the chain tensioner is broken.

JSP242

Thanks for chiming in. After I swapped the cam position sensors around I got a multiple misfire code for cylinders 6 & 8 after initially firing the engine. I had cleared them and tried to duplicate the codes before starting to diagnose the misfires by swapping plugs/coils around etc., but then the cam position sensor fault came back that I've had and no other codes.

From what I've been reading, it sounds like all 4 holes in the oval plates on the cams are supposed to be directly in line. I held a string across the outside 2 holes. The viewing angle is not good enough to say for sure, but that's why I was thinking it's a bit off. With the high compression numbers on the driver side bank, I'm guessing the valve are closing a bit early causing it to move to a quasi Atkins or Miller cycle combustion. So if I'm correct about them closing early, then that also means they have to be opening a bit early on the other side of that. That's good in that the valves would be out of sequence as the piston is moving away from the head thus minimizing the risk of valve/piston damage.

With your guess at the final diagnosis, that could make sense. I was wondering how the timing could slip or be off in the direction of the valves closing early. Normally when an engine skips timing, it's in the other direction. A broken or damage chain tensioner guide could possibly explain that. My question then becomes what is the procedure for doing the timing chain work? I haven't found that in the PDF copy of the Bentley that I have. Would I be correct in assuming that the torque at which I would tighten the new tensioner would have an impact on the force/tension on the chain? What is the correct way to confirm that the chain has maintained the correct relative clocking between the intake and exhaust cam?

And I'm still trying to locate the correct tools to lock the timing in place to check and verify.

4Driver4

You're making the assumption that the belt was installed correctly. Plenty of people try to cheat and do belt services without the tools. They think that making the cam positions is good enough. Usually it is good enough for the car to run without codes...but it's still not correct.

I would get a bar and pin and set the timing, but I still think your issue in under the valve cover. ;-/

JSP242

I was starting with what's the easiest and least invasive way to diagnose the issues. So I did start by swapping the sensors around because that was the fault code. I wanted to see if the fault code would move with the sensor or not. When I ran the engine first, I had the multiple misfire codes, but no cam position sensor fault. So I wanted to make sure the multiple misfire codes were repeatable before digging into that and chasing it down. Those didn't come back, but the original cam position fault did come back. So that confirmed my suspicion that there is an issue with the actual timing.

That's what's lead me to want to track down the timing locking tools to check/verify that the belt was installed correctly. My guess is that it wasn't. So if the belt is currently not correctly set, and then I reset it. What symptoms would I have if the chain tensioner is bad? Would it show some faults immediately still, or because the cam is back in time, will it take a while for it to show any other faults? If I decide to just dig into the valve cover right away while I'm at it, what do I need to be looking for in order to verify the chain position between the cams, and the tensioner condition?

4Driver4

Just to be clear, I think your troubleshooting steps and methodology is dead on. No criticism of that at all.

That said, you certainly can't hurt anything setting the belt right, but it probably does make sense to pull that valve cover and take a look. It would kinda suck to spend all that time putting the timing belt back together only to find that the problem persists. Check the chain timing when you get the cover off and take a peek at the adjuster guides. Look very carefully; usually it's the bottom guide that fails and it can be very hard to see.

One other thought: when you are looking at the oval plates, are you only comparing them to each other, or can you see the TDC mark on the harmonic balancer (aka crank pulley) too?

JSP242

Yeah. I've been debating about pulling that valve cover just to see if I could find anything. I'd rather not pull it apart if I don't have to, but I was wondering if just pulling the cover would be enough to see what I'd be wanting to see anyway, or if I have to disassemble part of the front of the engine to be able to inspect that chain tensioner.

Right now I'm only looking at the oval plates compared to one another. If they are supposed to be completely in line with one another, it should show that at the TDC and also with them rotated 180 degrees. Obviously when I get a hold of the tools, I'll make sure I have it set at TDC to set them.