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Audi A8 with LOTS of new parts soon parting out

Old 08-23-2018, 03:20 PM
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Default Audi A8 with LOTS of new parts soon parting out

So I'm throwing this one last effort at it. I cleaned out all the injectors and bought cataclean in an attempt to fix the misfiring im getting after the awful timing job. This car's got so many new things in it, its got the notorious hydraulic oil leak taken care of. It's got the timing done. It's got a brand new transmission in it, something thats pretty much expected to fail at around 180000 miles. I've got an extra master cylinder, i've got new calipers on the rear, just refurbished a bunch of vacuum hoses, new cabin air filters, new battery, CD player, a few new coil packs, all new iridium sparkplugs, new all season tires, some refurbished injectors coming in soon. I've seen the cams on this baby and they look brand new, i can't see any sign of wear on them, they still have the little machined ridges on their beveled edges. Bose sound system. I'll update you guys on how this last ditch job goes, if it doesn't work then you'll be the first to know about what parts I'm selling. Thank you again for all the help, it's been a journey of learning so much about cars.

I'm more than willing to sell these parts to you guys for very cheap.
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Old 08-23-2018, 05:31 PM
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When was the last time the fuel pump was replaced? After 100k miles, you're on borrowed time. Did you mention in an earlier post that sometimes it would run OK, then not, then OK again for a while? No codes at first,but when the pump is mostly dead, you can see multiple misfires from weak mixture.

Also, when 4 cylinders of a 32valve engine is acting up, the likely culprit is a bad POS (Power Output Stage). Cheap, easy to replace and a common known issue on the 32V engines.Those would be the first thing I'd check. There are two of them. Each feeds 4 coils.

This ain't the space shuttle. Suck, Squish, Boom, exhaust, repeat. Maybe find a competent mechanic to plug in VAG com, see what the eff is going on, do some basic diagnostic work, apply some logic and problem solved. It would would drive me crazy not to know why.

Good luck with whatever you choose.

Brian

Last edited by BrianC72gt; 08-23-2018 at 11:54 PM.
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Old 08-24-2018, 08:28 AM
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Originally Posted by Captain Sweeney View Post
So I'm throwing this one last effort at it. I cleaned out all the injectors and bought cataclean in an attempt to fix the misfiring im getting after the awful timing job. This car's got so many new things in it, its got the notorious hydraulic oil leak taken care of. It's got the timing done. It's got a brand new transmission in it, something thats pretty much expected to fail at around 180000 miles. I've got an extra master cylinder, i've got new calipers on the rear, just refurbished a bunch of vacuum hoses, new cabin air filters, new battery, CD player, a few new coil packs, all new iridium sparkplugs, new all season tires, some refurbished injectors coming in soon. I've seen the cams on this baby and they look brand new, i can't see any sign of wear on them, they still have the little machined ridges on their beveled edges. Bose sound system. I'll update you guys on how this last ditch job goes, if it doesn't work then you'll be the first to know about what parts I'm selling. Thank you again for all the help, it's been a journey of learning so much about cars.

I'm more than willing to sell these parts to you guys for very cheap.
A side note to any interested in parts and especially the transmission:

Unless you have more than one A8, this is a '97 3.7 with front wheel drive only(?) ... different trans than most all other A8's here.
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Old 08-24-2018, 11:10 AM
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Originally Posted by BrianC72gt View Post
When was the last time the fuel pump was replaced? After 100k miles, you're on borrowed time. Did you mention in an earlier post that sometimes it would run OK, then not, then OK again for a while? No codes at first,but when the pump is mostly dead, you can see multiple misfires from weak mixture.

Also, when 4 cylinders of a 32valve engine is acting up, the likely culprit is a bad POS (Power Output Stage). Cheap, easy to replace and a common known issue on the 32V engines.Those would be the first thing I'd check. There are two of them. Each feeds 4 coils.

This ain't the space shuttle. Suck, Squish, Boom, exhaust, repeat. Maybe find a competent mechanic to plug in VAG com, see what the eff is going on, do some basic diagnostic work, apply some logic and problem solved. It would would drive me crazy not to know why.

Good luck with whatever you choose.

Brian
I just cleaned the injectors manually and now it runs a little better. Looking underneath, I can see that only the right catalytic converter is smoking, which leads me to believe that that sides the one that's clogged. Strangely enough the opposite side of the engine is the one that's misfiring. I can hear what sounds like dripping, maybe its just metal flexing, but i dont see anything undernearth the car dripping. If i hold the gas at the lowest level it'll stay at without stalling, it'll float at a certain rpm, then jump a few hundred higher for a moment then fall back down again. I have to hold the gas down for it to run at all. Sometimes ill hear popping too, like the sound that those nice racecars make downshifting. Maybe the ECM is trying to compensate for the higher pressure on the right side? Idk it's a guess, does this make any sense? Do these details help at all?
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Old 08-24-2018, 11:11 AM
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Originally Posted by silverd2 View Post
A side note to any interested in parts and especially the transmission:

Unless you have more than one A8, this is a '97 3.7 with front wheel drive only(?) ... different trans than most all other A8's here.

I just cleaned the injectors manually and now it runs a little better. Looking underneath, I can see that only the right catalytic converter is smoking, which leads me to believe that that sides the one that's clogged. Strangely enough the opposite side of the engine is the one that's misfiring. I can hear what sounds like dripping, maybe its just metal flexing, but i dont see anything undernearth the car dripping. If i hold the gas at the lowest level it'll stay at without stalling, it'll float at a certain rpm, then jump a few hundred higher for a moment then fall back down again. I have to hold the gas down for it to run at all. Sometimes ill hear popping too, like the sound that those nice racecars make downshifting. Maybe the ECM is trying to compensate for the higher pressure on the right side? Idk it's a guess, does this make any sense? Do these details help at all?
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Old 08-24-2018, 12:08 PM
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Timing correct? Valves not bent (compression readings with throttle open and fast cranking)? Get some error codes from your OBD2 port, clear them, then see what returns. If you have multiple misfires from bad ignition, the fuel doesn't burn in the engine, but does burn in the exhaust/cat. Swap coils around and see if misfires move or stay where they are. If they move, bad coils, If not, bad POS. My bet is the POS (1 or both) is one of your problems. If all the misfires are on the same bank, and they don't move with coil swap, then maybe CAT or cam timing. If the misfires are random and move all around, then the fuel pump is another strong possibility. Those are your top two: POS, then depending on symptoms/codes fuel pump, or CAT, or vacuum leak, or a bad wire or...lots of stuff, but focus on the misfires, stay on that one issue, and you will get an answer.
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Old 08-24-2018, 01:28 PM
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The history on this car is you bought it not running, yes?
While you owned it, did it ever run smoothly, even for a short while, because that would rule out things like cam timing.
Bad cam timing is not intermittent. Failing ignition and fuel pump are.
What's the back story? Why did the prior owner have it off the road?
Did it ever run ok since you owned it? If so, what happened? Sudden failure, intermittent symptoms??
VAG com would help with a deep dive because you could datalog sensor readings, but not essential. What have you got by way of a coed reader?
Where are you located?
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Old 08-24-2018, 01:40 PM
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Originally Posted by BrianC72gt View Post
The history on this car is you bought it not running, yes?
While you owned it, did it ever run smoothly, even for a short while, because that would rule out things like cam timing.
Bad cam timing is not intermittent. Failing ignition and fuel pump are.
What's the back story? Why did the prior owner have it off the road?
Did it ever run ok since you owned it? If so, what happened? Sudden failure, intermittent symptoms??
VAG com would help with a deep dive because you could datalog sensor readings, but not essential. What have you got by way of a coed reader?
Where are you located?
It ran beautiful for a time. Here's the timing. That's TDC, left side, the misfiring side that tour seeing


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Old 08-24-2018, 01:42 PM
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Originally Posted by Captain Sweeney View Post
It ran beautiful for a time. Here's the timing. That's TDC, left side, the misfiring side that tour seeing

Looking at it again, you see those little brown marks behind the circles? Do those have to line up too? ItsI hard to tell if the circles point to specific teeth, or if the etched circles align with the brown circles on both sides all in a line. Idk tbh.
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Old 08-24-2018, 07:06 PM
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The brown circles just make it easier to find the etched ones. The etched circles are your timing marks. The spark requires a good timing signal (N80), good coils, good spark plugs, and good Power Output Stages (POS) also called Ignition Control Modules.

The power output stages are a frequent point of failure. You can find
replacements on Amazon for $23 replacements on Amazon for $23
., and free shipping with Prime. You'll need two of them. The next place I would check is the fuel pump.

When checking for multiple misfires, I would move the coils from the cylinders where the errors are occurring to a position where there are no errors. If the errors moved with the coils, than the coils are suspects. If the errors stay at the original cylinders, then check the power output stages, and if all the errors are in the same bank, the cam timing or fuel pump.

Last edited by BrianC72gt; 08-24-2018 at 09:19 PM.
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