mrgriffith

Did A timing belt 6 Months ago. Car returned with a oil leak front of engine. Pulled timing covers. T-belt was oil soaked. fixed oil leak and installed new T-belt and started car everything was fine intill car came back from alignment
shop.Checked out car and pulled all codes and found it had multipule codes set. For missfires on cyls 1-4-6-7. Started out double checking myself and rechecked all the timing marks. Reinstalled the cam tools and checked the TDC mark. Everything lines up. Checked compression and have 200 psi accross the board. With the plugs
removed I checked that when #1 was at TDC the mark also showed that it was.
No leaks at intake so I pulled the valve cover off to find that when I installed the cam holders that the left
cam does not line up the marks on the chain sprockets.

The right one is right on. So do I have a problem or do I just make sure that the tool just lines up in the head and dont worry about it. The marks do line up if you turn the cams. just not with the tools installed.But as I also saw the the Ignition timing was moving all over the place. Not steady like all the other cars I've seen. The Idle is also ranging between 1300 to 1900 by the scanner. engine is running faster than idle and
have no codes set yet.
But my ignition timing is still ranging between 5 atdc to 29 btdc. still the same story. It almost sounds like
the ECM is at fault.
I was looking at the patterns for the cam and crank sensors and the vantage has a cam and crank sync pattern test. But I have nothing to compare it to. Does anyone know what the wave forms are suspose to look like. I have one I pulled from the vantage.
But I dont know how to post it. Ive checked the timing belt and made sure it was aligned right three times
now. It still comes up with missfires on #1-4-6-7. # 4 is set first. And you can watch it count up on the
scanner. So what Im thinking is that the timing is off. But I cant see where.
So we got a t-belt from the dealer, installed it and tripple checked the alignment. And still i have the
same pattern from the cam and crank. I was told that the marks lining up the cams by the chain are to
align also when the 3341 tool is installed. Mine dont. There off a little. Is that a concern?? Also when
checking out why my readings are all over the place, we went to the maf and tested it with the vantage and
found that the readings were steady at 0.91 volts when the scan tool is saying it is varying between 3 to 12
gpm. When you accelerate the engine the voltage climbs at a steady rate and returns to 0.91 volts. Also when I disconnect the TPS my reading settle down And the engine runs smoother than with it pluged in.
Has someone had this problem before. I'm turning gray over this thing
Thanks

Pete@ECSTuning

There are marks on the top of the cams near the gears right by the chain that indicate TDC. Your repair manual should tell you how many links separate the TDC marks on the gears. IS: From TDC tooth to TDC tooth on each cam should be separated by X amount of chain links. It sounds like a cam is off 1 tooth on the chain to me.

mrgriffith

I already pulled the valve covers and the marks on the cams line up just as the manual says. This engine doesnt have a tensioner on the chain. So Everything is lining up just as the manual states. And I rechecked the the t-belt three times with the cam plates. So I dont see how the timing belt is off. Any other Ideas why my ignition timing by the scan tool is going all over the place. And my MAF sensor is also going all over the place. By the scan tool the RPM's are also going up and down and the engine is idling good when I disconnect the IAC.

Pete@ECSTuning

You may have a bad IAC and the timing belt job is coincidence. I'm not terribly up on my A8 stuff, but is it possible to clean/inspect your IAC?

mrgriffith

So on friday a guy came by tochech out the A8 and said the cam timing is off. I rechecked the timing over three times. And find nothing wrong. What could have happened t make the sync between the cam and crank to be off. The only thing I can think of is that the cam gears for the chain drive is coming apart. If that is possible. But how do you prove it. I need other idea's I'm getting to brain dead. Thanks

silverd2

I don't have a theory, but others here may need more info to help.
What year/engine A8?
How did the guy decide the cam timing is off, when you said the T-belt timing checks out? What did he check?
Did a mechanic do first belt job and you did later repair after oil leak?

All the codes and rpm flux just don't sound like a mechanical cam timing thing...unless something is really moving around.

silverd2

P.S. noticed you said T-belt lined up, but chain sprocket on left under valve cover was off? Did you pull the outer sprockets to do belt the second time?

mrgriffith

Its an 1999 A8 With a 4.2l V8. And the guy used a modus with a pressure transducer on two cylinders. and ran the engine and maped out whem the compression stroke and the exhaust and intake valve were opening to determane the relation to the crank. and you can see that the timing on one bank is off from the other. and yes i always remove the timing belt scrokets when doing a t-belt

tozoM8

Your T-belt is off a tooth or two. You need to lock the crank, lock the pass side cam, loosen the eccentric roller so you can turn the driver's side cam and lock it. Now you can loosen the driver's side sprocket, tension the belt properly and tighten the sprocket. If you think that the pass side cam is off too then loosen both sprockets, tension belt and re-tighten the sprockets.

mrgriffith

how do you lock the crank