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Discussion Starter · #1 · (Edited)
Hello, appreciate any advice from the field...

After recently having timing chain service done at 110k mi., my Touareg developed a slight stumble/flutter at idle. One cold start after a long highway ride, and a hard "miss" emerged with flashing CEL resulting in a rough ride at any RPM/speed.

I drove it home limping and replaced all coils which took care of the misfire & CEL. The same slight flutter was still present at idle, but the test drive was smooth. After about a week and a couple hundred miles the CEL came back on and the engine started misfiring again, less severely than before the coils were replaced, and only occasionally.

Took it to the VW dealer because it was due for an oil change (the problem was mainly an annoyance) and they did plugs, fuel filter, and other general maintenance items (over $2k) and they gave it back to me with the CEL on full-time. I sent it back to them and they spent a few days troubleshooting with VW of America assisting. Finally came back to me with a diagnosis that cylinder #1 is misfiring and shows low compression (they said 70 PSI). They didn't scope it or anything, said an engine swap was probably my only option--said it could be a failed ring or piston and VW doesn't supply those parts for repair. They offered me about $2k trade-in value which I declined.

I took the Touareg to a reputable independent VW/Audi garage--the one who did the timing chain--and they reported compression 'a little low' in cyl #1. They think it's due to carbon deposits on the intake valve(s). Didn't scope it or do any comprehensive diagnostics. They said they didn't think a new engine was necessary. Recommend dropping the engine and cleaning the valves (~$3k job). I asked about fuel additives, etc., and though they don't think it will work they said I should try it before committing to an expensive job. They mentioned Techron over alternatives like Seafoam based on reputation. I ran one bottle of Techron through the fuel system so far, cleared the misfire code with VAG COM, and the CEL still occasionally appears/disappears a couple hundred miles later.

Other details: have been running regular grade fuel, dealer-maintained w/oil changes on recommended schedule, has mainly been used for long weekend drives until a few months ago when we started using it for daily commutes ~30mi each way. Prior to this, the CEL was never lit in the 5 years that I've owned the vehicle.

Thanks.
 

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Hmmm.... Not sure why you need to drop the motor to clean the valves. I thought the intake came off and you could get to them that way?

An regular CAN bus OBDII reader can pull CEL codes for you, but VCDS can delve into the modules and sometimes give you a clearer picture of what's going on.
 

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Hello, appreciate any advice from the field...

After recently having timing chain service done at 110k mi., my Touareg developed a slight stumble/flutter at idle. One cold start after a long highway ride, and a hard "miss" emerged with flashing CEL resulting in a rough ride at any RPM/speed.

I drove it home limping and replaced all coils which took care of the misfire & CEL. The same slight flutter was still present at idle, but the test drive was smooth. After about a week and a couple hundred miles the CEL came back on and the engine started misfiring again, less severely than before the coils were replaced, and only occasionally.

Took it to the VW dealer because it was due for an oil change (the problem was mainly an annoyance) and they did plugs, fuel filter, and other general maintenance items (over $2k) and they gave it back to me with the CEL on full-time. I sent it back to them and they spent a few days troubleshooting with VW of America assisting. Finally came back to me with a diagnosis that cylinder #1 is misfiring and shows low compression (they said 70 PSI). They didn't scope it or anything, said an engine swap was probably my only option--said it could be a failed ring or piston and VW doesn't supply those parts for repair. They offered me about $2k trade-in value which I declined.

I took the Touareg to a reputable independent VW/Audi garage--the one who did the timing chain--and they reported compression 'a little low' in cyl #1. They think it's due to carbon deposits on the intake valve(s). Didn't scope it or do any comprehensive diagnostics. They said they didn't think a new engine was necessary. Recommend dropping the engine and cleaning the valves (~$3k job). I asked about fuel additives, etc., and though they don't think it will work they said I should try it before committing to an expensive job. They mentioned Techron over alternatives like Seafoam based on reputation. I ran one bottle of Techron through the fuel system so far, cleared the misfire code with VAG COM, and the CEL still occasionally appears/disappears a couple hundred miles later.

Other details: have been running regular grade fuel, dealer-maintained w/oil changes on recommended schedule, has mainly been used for long weekend drives until a few months ago when we started using it for daily commutes ~30mi each way. Prior to this, the CEL was never lit in the 5 years that I've owned the vehicle.

Thanks.
What do you think will be achieved by "scoping" the engine?

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Discussion Starter · #4 ·
What do you think will be achieved by "scoping" the engine?

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For me as a customer I think bore scoping would help rule in/out mechanical failure in the affected cylinder which the dealer seemed to think was the problem (cracked piston, ring, etc.) causing low compression. I want as much info as possible before considering a $12k engine job (dealer quote) or $3k valve job. Leakdown test, too.
 

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Discussion Starter · #5 ·
Hmmm.... Not sure why you need to drop the motor to clean the valves. I thought the intake came off and you could get to them that way?

An regular CAN bus OBDII reader can pull CEL codes for you, but VCDS can delve into the modules and sometimes give you a clearer picture of what's going on.
I don't know if there is a difference between FSI and non-FSI (mine) in that regard, but the shop is telling me they need to drop the trans, etc. to do it.
 

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That's right you're non-FSI.

The fuel is sprayed into the manifold and thus can clean the valves, so I'd run some BG K44 cleaner (put in gas tank) through it first. Might take a few tanks to do the trick, but with the V8's gas mileage, you can go through a few tanks of gas pretty quickly! LOL!

I know you've already run one cleaner through. But if it's really gunked up, it might take a few bottles.

Also, doesn't the manual specify premium fuel?
 

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For me as a customer I think bore scoping would help rule in/out mechanical failure in the affected cylinder which the dealer seemed to think was the problem (cracked piston, ring, etc.) causing low compression. I want as much info as possible before considering a $12k engine job (dealer quote) or $3k valve job. Leakdown test, too.
Well a scope and a boroscope are different tools. If you had a cracked piston it would never stop misfiring. It's possible but unlikely you have carbon buildup. Does the engine misfire after a cold soak? (12 hours + of not running) If yes does the misfire go away after warmup?

Why are you using regular fuel? It calls for 91octane or better.

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Also did you have a timing chain done or a timing belt service? For your engine there is no maintenance for the chains.

I feel you may be ignorant to what is actually going on with you car. (I do not mean this offensively)

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Discussion Starter · #9 ·
Also did you have a timing chain done or a timing belt service? For your engine there is no maintenance for the chains.

I feel you may be ignorant to what is actually going on with you car. (I do not mean this offensively)

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You're right, my mistake--service was timing belt.

I wouldn't be on here if I knew what was going on with it, so yes, I am ignorant about it and I suspect at least one certified mechanic I've dealt with is also ignorant about it so at least I'm in good company.

I meant boroscope, to see what's going on physically that might be causing low compression. The dealer's mechanic suggested the piston might be cracked or that there might be a problem with the ring(s). They had consulted with VW of A to try to diagnose/solve it.

The misfire seems to occur after/during long drives, e.g., after slowing down in traffic. On cold starts there is a slight 'flutter' at idle which had not been there before the timing belt job. The misfire code/CEL usually does not trigger after a cold start. It seems to be random; I'll take 30-minute mixed highway/city drives in temps around freezing and see/feel nothing unusual w/no CEL.

(I'm using premium *now*.)

Thanks.
 

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A cylinder leak down test needs to be done for that cylinder, I suspect a burnt valve/valve seat. I could be wrong but a leak down test will confirm.

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Discussion Starter · #11 ·
I haven't had a leakdown test done yet, but having driven for a few weeks since last post, the Touareg runs great 90% of the time, but then it will start misfiring and running rough. Almost as bad as before I replaced all the coils. Shutting down for a little bit and starting up again, the car is back to running 100%. Seems more like an ignition issue than a mechanical issue, no? I expect that some sort of mechanical issue (including carbon deposits) would result in consistently poor performance. Latest scan shows piston #1 misfire code as well as random/multiple misfire code.
 

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Discussion Starter · #12 ·
It was carbon

Shop was able to remove the head without dropping the engine, and found that the exhaust valves on cyl #1 had excessive carbon deposits. Replaced the valves and the misfire went away. I had tried both BG 44K and Techron prior to the valve job--no luck.
 

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Shop was able to remove the head without dropping the engine, and found that the exhaust valves on cyl #1 had excessive carbon deposits. Replaced the valves and the misfire went away. I had tried both BG 44K and Techron prior to the valve job--no luck.
Ouch, good to hear you're up and running!
 

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I also tried the bg44 and BG intake cleaning at a shop. Also no luck. Had to clean the carbon manually.
 

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Interesting that you still had carbon buildup, despite your engine NOT having direct injection. In theory, your engine should have the fuel mixture spraying into the combustion chamber via the intake valve. That is supposed to help keep it clean. Hmm....

Fuel system cleaners won't prevent carbon on an FSI engine. Fuel is injected directly into the combustion chamber, bypassing the valves.

To the OP: Hopefully you've switched to premium fuel. Your engine will be happier. And so will you, when you find more horsepower and torque in your engine. :- )
 
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