myhobosoul

<center><img src="http://static.flickr.com/59/169596592_82df11136f.jpg"></center><p>I recently replaced the timing belt on my 4.2 97 A8.

Although I had the special tools, I couldn't get both camshaft locking tools to engage simultaneously. The driver's side would lock into position when the crank was at tdc, but the passenger cam wouldn't lock into position until the crank had rotated about an inch and half past TDC. Btw the car ran great!

Foolishly, I thought by adjusting the timing so that both tools locked into place at the same time that the crank was at TDC would be an improvement. This meant I turned the passenger side cam about two teeth forward so that the it would engage with the camshaft locating fixture when the crank reached TDC.

Car ran poorly. But there were no DTCs. The check engine light never came on.

I took the front end off again, and removed the valve covers. This time I set the timing so that when the crank is at TDC, the indcator dots on both sets of cams point towards each other.

It runs slightly better, but still does not have the jowel lifting torque that it had before and it now has a check engine light. The VAG reads a 17800 P1392 Camshaft Position Sensor. I followed the bentley procedure to check the sensor. It seems fine, so the Bentley suggests, check the toothed belt adjustment...

Question:

Am I incorrect to assume that when the dots on the cams point to each other that they are where they should be when the crank reaches top dead center? I no longer have the camshaft locating fixtures. How should I go about getting the engine in time? Should I return the passenger cam to the previous position which was two teeth behind the crank? Why didn't this put the exhaust valves at risk since they don't close until 2degrees BTDC?

This picture shows where the crank was with the passenger cam locked in position, before I removed the old belt.
Bewildered.

ub2slw

that you were TDC on the # 1 cyl and that you were at the top of the compression stroke and not the top of the exhaust stroke? It sounds like you were at the the top of the exhaust stroke if the exhaust valves would close 2 deg before TDC.

myhobosoul

<center><img src="http://www.icshelp.tzo.com/software/a8picts/DSC00789.JPG"></center><p>These are the marks, should they be like you see them when the crank is at TDC for the intake stroke?

As for the 2 degrees BTDC on the exhaust valves, that is a spec listed in the Bently Manual. I only mentioned it to highlight how little room for error there is. I was surprised to find the passenger cam so far out of time when I took everything apart, but as I said, the car ran excellently.

The real question I have is: with the valve covers off and looking at the camshaft gears with the crank at TDC, are the cams at TDC for the intake stroke when the circular markings on the gears are pointed at each other? That is how I currently have the timing set. On the intake stroke the circles converge and meet when the crank is at TDC.

ub2slw

The dots should be straight up on the compression stroke with the #1 cyl at TDC...how were you making sure that you had the #1 cyl at TDC of the compression stroke? some engines (don't know if the v8 is like this) one cam gear mark may be straight up and the other straight down on the compression stroke, which you would want to go one more to get to the overlap and both the dots should be pointing straight up...

myhobosoul

I dont think its possible for both dots to be pointing up at the same time. With the two dots on the passenger side intake and exhaust cams pointing inward towards each other and the crank at TDC, the intake valves for cylinder 1 have been closed for a while and the exhaust valves are getting ready to open. I'm pretty sure its very close the way I have it set now, just from a visual inspection of the cam lobes in relation to the lifters, and from the fact that it idles very smoothly.

How do the dealers get the cams back in time if a belt breaks? The audi dealer I went to had never heard of camshaft locating fixtures. They just paint lines on the belts when they change them! They also mentioned a line on the camshaft caps and on the shaft itself that could be lined up. But after a long hard look, the only marks I see on the cams are the two sets of circles.

ub2slw

pull the spark plug on the #1 cyl and stick a straw down there (the cyl on the passenger side closest to the headlight right?) Turn the crank until you reach TDC and the staw is pushed up. Check the cam that you didn't move to see if the circle is straight up, you may have to keep turning the crank until you get to the comp stroke of the #1 cyl and the dot on the right side pointing up.... see if the other cam is close to pointing up...

myhobosoul

Good Call, thats what I did. The crank index was 28 degrees off. Reindexed it, problems solved.