4000skq

I just did a timing belt on an A8 and am having trouble getting the motor to run smooth. All measure block values look good and it passes all of its readiness test. The motor runs but has a miss feel to it. Ive had the belt off twice. The first time I put it back together it wouldnt start(I did turn it over by hand and check for valve interference)I took it back apart and my marks where off. So I set it back up checked for interference and it started. It ran rough so i checked my marks again. This time it was off by about 10degrees. So its back apart again and im just wondering how it could have come out of time 10degrees. I rolled it over about 3 times and there was no interefence and my marks looked good. Im going by the procedure in mithcelle and alldata. I just wanted to see if there were any tips someone had or btdt experience. Like i say the car runs fine it just seems to have a slight miss. No codes and all measure block data looks good, o2, mass air, 02 adapat, readiness. Any info would be appreciated. And i have tried 2 different types of plugs. Thanks
=dustin=

PaulW

Or did you just mark everything before you took it off?

If the later, then your problem is with the timing between the cams and the crank. Every TB change I have performed, they have all run much smoother after the change.

4000skq

thats whats bothering me about going 10 degress out. Everything lined up nice and the tools slid in and out real nice on both cams. Thanks for posting though.
=dustin=

PaulW

You said initally it wouldn't start......what was the cause? I would think electrical such as a connector not be put back on the cam sensor or the such.

You then took it apart and your marks were off, what marks are you referring to? I do not remember any marks on the engine.

What was 10 degrees off? How did you measure this?

Tensioning of the belt to the exact measurement of the damper is not easy. I normally excercise it a few times and then go very slowly (like at least 1 minute) to get the tensioner correct. When you are doing this, you need to have the cams loose on the shafts also.

4000skq

i wouldnt start because the cams were out of time. The mark i am refering to is the crank mark. i know the cams dont have marks, it was a mistake for me to say marks. I should have said the crank mark was off when i put the cam tools in. I measure 10 degress as a guess, when i have to move the crank to get the cam tools in the TDC mark on the crank was ABOUT 10 degress off. What you said about the tensioner was interesting as we just compressed it and set it, measured with a tape measure. HA! i dont understand what happened either. We do plenty of 1.8,2.8,2.7 belts but this is the first 4.2 or v8 for that matter.

thanks again.
=dustin=

PaulW

I wouldn't set mine with a tape measure, but that's just my $0.02.

And I had to re do mine three times because I did it on a hot motor. If you are setting this thing up and had the motor running at all today, the measurement is different, and I believe the Bently is wrong.

You have to set it while the motor and tranny are at ambient temps.

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/tbp50.JPG">

use a set of calipers to do this.

I would put the cam tools in, unlock the cam sprocket from the cam shaft, make sure the engine is at ambient temp (leave it overnight if it is not), set crank shaft TDC, then tension it. Make sure it's correct before locking the cams down, it takes a few minutes to get to it's final position.<ul><li><a href="http://www.audipages.com/Tech_Articles/enginemechanical/tbreplace0.html">And I assume you have seen the audipages procedure</a></li></ul>