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2000 A8 performance issue - timing?

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2000 A8 performance issue - timing?

  #1  
Old 12-09-2010, 04:20 PM
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Default 2000 A8 performance issue - timing?

Now that I got my wife's car sorted out, I want to take a look at mine. It's the same year with 100k less miles. Her car has much faster acceleration and feels like my last Audi (also a 2000 A8 - totalled from engine fire). It doesn't have that kick/downshift "push you back in the seat" when you floor it.

It's been like that ever since I got it about 30k miles ago - mileage is 90k. I have an occassional "Bank 2 lean intermittent" code which I haven't tracked down yet. I'll reset it and it sometimes stay off for months so I assume that's not it. I'm figuring a minor vac leak/line.

Otherwise it starts and runs great but the idle is slightly rougher (front mount was replaced) especially with the A/C/Heat off.

I'm suspect of the timing being slightly off if the shop did it by marking the belt. They did a couple of jobs more than once so that's part of my thinking. My question is can the timing be off and NOT throw a CEL?

I suppose I can lock the crank and just see how the cam lock bar fits. Is there a measuring block that will do the same thing with vag-com?

MAF, air filter, pre cat o2's, fuel pump and filter all new, no change. I've also cleaned the throttle body and fixed the intake runners (was sure that was it) but still no change. I haven't actually pulled a plug(s) to see what they used but they were changed at the same mileage as the timing belt job, about 30k miles ago.

Any ideas?

Bob
 

Last edited by A8CT; 12-09-2010 at 04:23 PM.
  #2  
Old 12-09-2010, 05:36 PM
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You hit on several of my guesses already....intake changeovers, MAF, etc. Would be worth checking belt timing with camlock tool. Yes, cam timing should record a code and trip a CEL within 2 driving cycles.

Just a couple of wild guesses related to rough idle and poor accel:
Fuel pressure regulator causing lean (fuel starved) condition...would need pressure gauge to check.

Knock control...which should (could) throw DTC, but if malfunctioning could severely retard all cylinders and result in dramatically decreased power. The only experience I've had with this was on a 1986 VW (before OBD2) and the result was smooth running but extremely poor accel. Wouldn't likely relate to rough idle, though. There's a procedure to check knock control with Vagcom.
 
  #3  
Old 12-10-2010, 08:24 AM
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Default speaking of fuel

I forgot to add one thing. When I first start the car and back out of the driveway, I hear a slow clicking/pumping sound coming from the trunk area. When I parted out my car, I remember removing something from under the spare tire well. That's where it sounds like it's coming from.

That assembly is part of the evap system correct? I've never heard that sound on a D2 before and not sure if it's part of my problem. It seems to stop after a few minutes. It could be doing it while I'm driving but I've never heard it before and not sure that I would over the road noise.

Isn't the fuel pressure regulator right up at the fuel rail on the pass side? I do have a fuel gauge, that's probably worth checking.

When I say "rough" it's very slight. Nobody but me or another D2 owner would notice the difference. It's nice having the exact same car in cases like this.


Bob
 

Last edited by A8CT; 12-10-2010 at 08:27 AM.
  #4  
Old 12-10-2010, 09:03 AM
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Without searching, not sure about the spare tire well, but shortly after start up, the leak detection pump (in the left rear fender well..outside next to top of shock tower) runs a leak test on the gas tank and evap system (pressurizes the system and times the bleed down...if a leak is detected, it runs a second test and records a code if a small or large leak is detected). But this system shouldn't affect performance.
Rough idle could be lots of things...underperforming coil(s), fuel mixture (O2 sensors?), etc..
Yes FP regulator under the hood, between fuel rail on passengers side and firewall..I believe(?)
 
  #5  
Old 12-12-2010, 11:46 AM
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Default cam timing

I'm onto my car, doing the TB job on that too. Got the crank locked and then tried to set the cams and the pins didn't quite line up. Perfect, just solved my lack of power problem. The car had the thermostat and WP changed before I bought it so they probably didn't set the timing correctly.

But wait, there's more

The 1/2 moon gasket has a pretty good leak under the tensioner so I was going to lift it up and replace it. Easy enough.

When the cams are locked though, the marks on on the ends of the cams and the cam caps don't line up. The bottom one (drivers side) is dead on but the top is off. I can rotate that cam a little and get it closer but can't get it dead on. I have the tensioner tightened now so I have slack on the chain.

I have about the same amount of grooving on the pads as I did on my wife's car but with about 100k less miles. No codes.

Does this mean the tensioner jumped time? They should be dead on with the cams locked correct?


Bob
 
  #6  
Old 12-12-2010, 01:19 PM
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[QUOTE=

Does this mean the tensioner jumped time? They should be dead on with the cams locked correct?


Bob[/QUOTE]


I thought so. Is it off as much as the distance of one tooth on a cam chain sprocket? Did your recent job line up exactly with the engine unpressurized and at rest?

Just a semi-educated (Ha) theory/ guess: The adjuster's amount of travel could change one timing mark in relation to the other. Does the adjuster appear to be at the same amount of extension as your recent observation of the other car?

The adjusters have an internal spring loaded locking pin to hold the chain tensioner's piston at a tensioning extension after the car is shut off and oil pressure dies. The purpose of this is only to prevent chain noise on start up...doesn't play any other role in normal driving operation.

I have always had a brief chain noise on very cold start up (never on warm start up), indicating that a pin has failed...this seems to be almost universally common among other 40V D2 owners eventually. Audi had a good idea with this, but seemed to have not built any longevity into that particular feature.

Don't know, but can picture, different extensions on the cam chain tensioner resulting in slightly different relation of cams to each other (which I understand to be the whole purpose of the system, anyway) resulting in at least one mark being slightly off....esp if it is off way less than than an entire chain gear tooth distance. Actually, without catastrophic failure of a cam tensioner, can't really picture how it could jump time on the chain (?)

Of course, all this is just guesses on the drawing board...not in actual practice.

Sam
 
  #7  
Old 12-12-2010, 05:47 PM
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this took a slightly different turn. I pulled up the tensioner to replace the 1/2 moon and metal gasket. I figured I needed to do that regardless and that would give me more time to think about the cam indexing being off and still get something done.

When I pulled it up, I saw the tensioner metal screen stuck on the hole. I checked my old one and it doesn't look like you can swap it with another one. So, I took my used tensioner from my old car (replaced and has about 40k miles) and am installing that one instead.

Somehow the cam timing marks did not line up with engine at TDC. I rotated the right side cam in order to lock them together and the top cam mark was off by probably two of the index "squares" on the end of the cam. I played with the slack in the chain and rocked the cams back and forth but it was off every time. I only took the valve cover off to change the seal otherwise I wouldn't have noticed.

And, when I locked the crank, the cam bar didn't line up either so the timing belt indexing was off too.

I think these are two separate issues. I've read about bad tensioners causing the cams to get out of synch but I'm not sure how. It doesn't seem possible that the chain could "jump" a link. I can see it if the pads broke but that wasn't the case here.

I don't see how the timing belt being off could cause the cams to get out of synch since they're connected by the chain?

When I did the one last week, I was able to get the cam marks dead on with the cams locked. That seemed to work, so I'll do the same this time. I am going to pull the valve cover off the pass side and hopefully those will be on the marks.


Bob
 
  #8  
Old 12-12-2010, 08:44 PM
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2 timing mark squares off almost sounds like an entire tooth distance(?). Did you count the links between the gears? Makes you wonder if the chain has ever been off...as I said, really don't know how it could jump time without a completely broken adjuster.

And timing belt off, too?

Really curious to see how it runs when all is timed correctly.

Also curious to hear if you have to move the chain a link over.
If the exhaust cam (outside/lower) is lined up with timing mark when the cam belt gears are locked, then the belt gear has to be properly seated...so what else could cause the intake cam to be that far off the mark?
 
  #9  
Old 12-13-2010, 02:57 PM
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yes, chain count and timing were off. I'm surprised that the cams were off because there's no record of anything being done internally. But, what I do have a record of for the car has been done multiple times.... i.e., thermostat, oil cooler, fuel sender, cluster. This between an Audi dealer and an independent shop.

I got the right side tensioner on the mark and set at 15 links with the tensioner tool removed. I rocked the cams back and forth a little and checked again. It's a hair off (still within the "box") one one side the other cam is dead on. From other posts I've read guys are saying that the # is links is the critical issue and not the cam/cap marks. I don't see how that's possible though because I "think" you could have it set at 15 (driver side) and still be off. The teeth on the cams don't know where the marks are

In my case, I don't think you can get it any closer because it would have to move at least one tooth and that would put it outside the mark (by a lot) in either direction. Again, I'm talking fractions....

I just pulled the pass side valve cover (cam bar installed) and it's dead on. I'm just lifting the tensioner up and replacing the gaskets on this side.

I hope this isn't one of those one in a million chance stories like the cam was mismarked at the factory

I'm waiting for parts to arrive so it'll probably be a couple of days before I can put it back together and turn it by hand a few times.

Bob
 
  #10  
Old 12-13-2010, 05:54 PM
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Sounds like you got things back where they belong...15 teeth on bank 2 and marks anywhere close has to be. But how bizarre that belt and chain were off...if the car could only talk...or maybe it has, saying "incompetent ***** have worked on me".
Once again, you would think the car would have recorded a timing code, but you may have seen PK's mention over on Qworld that he had a seized cam tensioner and never threw a code...I don't get it(?).
Bet you can hardly wait to drive the corrected version of your engine...as you've said, even a stock A8 should set you back in your seat when asked to.

Sam
 
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