2009 A4 B8 2.0T Cylinder 4 misfire

[PuddlingNuts]

I'm having this issue recently, only after driving long distances, the "check engine" pops up and then the EPC light is on.
There's no power and the car shakes when I hit the gas.
Error: Cylinder 4 misfire

A temporary fix would consist in cleaning the spark plug electrode, which has oil on it.
After that, the car runs fine for a while - approx. 600 miles.

Other issues & notes:
- the car is burning oil, approx. 1L every 1500 miles.
- the engine was rebuilt at 125.000 miles - new pistons, rings, valves, etc.
current mileage 208k

Parts changed so far:
- spark plugs
- PCV valve

What could be the issue now? Thanks!

[MongoMcG]

Which conditions trigger the misfire? If under load it could be coil packs, or VVT actuator, or fuel injector, or fuel pump, or low coolant, or carbon build up on the intake side, or bad gasoline, or...

At 83,000 miles since the rebuild, it likely time for a new timing chain and tensioner. Here's how to check the timing chain tensioner through the peep hole in the front of the lower timing chain cover. This video is for a VW which has some extra plumbing (boost pipe) in front of the peep hole that the B8 does not have, but the procedures (if not the angles) are the same. You can skip to 1:22 min mark. to get to the meat of the video:


There is information on this forum and elsewhere about tensioners (old and new style) and plenty of info for taking on the task of replacing the chain yourself, if you're inclined. DIY timing chain replacement is a huge $ saver, but it's not for the faint hearted. If you do not have the factory service manuals, a one day subscription at https://erwin.audiusa.com is $35 and you can download PDF's of the FSMs, TSBs, and more for your VIN. On the top navigation menu for the page, point your mouse to "My Account" and select "Subscriptions". I don't remember much past that point, but you're a grown up; you'll figure it out.

If the timing chain has stretched near the max capacity for the chain tensioner you are flirting with catastrophic engine failure. If the timing chain stretched enough then the chain may skip a tooth or two. The 2.0L TFSI is an "interference engine", so if the chain skips then the valves (camshafts, actually) are out of time with the crankshaft, and when the pistons are shoved to the top while the valves are still open, BAM! empty bank account. Scary thought, but peruse the forum and you'll see it is not uncommon.

There are software solutions (VCDS et al) that can measure timing chain stretch. There's a rabbit hole for that here:
https://www.audizine.com/forum/showt...hain+cam+phase

The reasons for misfire are many, so if you can help nail down when the cyl 4 misfire is happening you'll get better and probably less scary advice.

[PuddlingNuts]

Which conditions trigger the misfire? If under load it could be coil packs, or VVT actuator, or fuel injector, or fuel pump, or low coolant, or carbon build up on the intake side, or bad gasoline, or...

The spark plug from this cylinder was found to have oil deposits right on the tip. So there's something wrong in the combustion chamber.
I scheduled the car for the regular oil & filter change and I'll ask for more diagnostics, maybe wet and dry compression tests? So we can get more insights.

Either way, I can't afford to rebuild the engine at the moment, I'll drive the car as less as possible after the oil & filter change; so I can buy some time until the next major repair.
Thank you for the suggestion about the timing chain and tensioner - I'll make sure I'll change it.

[MongoMcG]

When the car is in for oil service ask the dealer will check the timing chain and test the coil packs.

More than a little oil in the cylinder could be from the bottom (piston rings), or from the top (valve stem seals), or from the PCV passing a lot of oil vapors through the intake manifold, or from the crankcase vapors that get passed by the PCV through the turbo and intercooler route. Oil in the cylinder could be the cause of your misfire, but it takes more than a little. What did the old of the plugs look like? Wet or dry parts, chalky or black, powdery or chunky? The dealer should give you a decent read on those if you ask. They can drop a borescope into the cylinder to see if oil is causing issues.

If the intake side of the cylinder has not had a carbon cleaning then chunks of carbon can get by the intake valves and cause misfires and other issues, including staying hot and causing the fuel to ignite early (a misfire), or scoring the cylinder wall, or burning a valve. Carbon cleaning was hopefully done during the engine rebuild, but at 83,000 miles since it could be gunked up again. If the carbon cleaning was not done at 125K mi then you are overdue, especially if your PCV has been spitting a fair amount of oil vapors through your intake manifold.

If coil packs are needed, steer clear of the cheapies from the large online bookseller.

[PuddlingNuts]

When the car is in for oil service ask the dealer will check the timing chain and test the coil packs.

More than a little oil in the cylinder could be from the bottom (piston rings), or from the top (valve stem seals), or from the PCV passing a lot of oil vapors through the intake manifold, or from the crankcase vapors that get passed by the PCV through the turbo and intercooler route. Oil in the cylinder could be the cause of your misfire, but it takes more than a little. What did the old of the plugs look like? Wet or dry parts, chalky or black, powdery or chunky? The dealer should give you a decent read on those if you ask. They can drop a borescope into the cylinder to see if oil is causing issues.

If the intake side of the cylinder has not had a carbon cleaning then chunks of carbon can get by the intake valves and cause misfires and other issues, including staying hot and causing the fuel to ignite early (a misfire), or scoring the cylinder wall, or burning a valve. Carbon cleaning was hopefully done during the engine rebuild, but at 83,000 miles since it could be gunked up again. If the carbon cleaning was not done at 125K mi then you are overdue, especially if your PCV has been spitting a fair amount of oil vapors through your intake manifold.

If coil packs are needed steer clear get the cheapies from the large online bookseller.

Thank you for your suggestion!

The last time I visually inspected the spark plugs, I only noticed black powder on them. But I didn't had a chance to visually inspect the old ones, which were changed approx. one month ago. The technician said it was an oil-burning issue.
Before the last engine rebuild, the car was burning a huge amount of oil with no misfires, approx. 1 litre every 200 miles.

I'll get oil & filters replaced in 3 days from now, I'll ask them to verify the timing chain. 🙏

[MongoMcG]

Good luck.

[redrackham17]

Which revision of the PCV did you switch to? If your car was never updated to the white top, you should have put in one ending with park number "AH" because it's the newest blacktop revision. Switching to the upgraded white top requires work on the ecu and the front crank seal. Also, how reputable is the piston ring job that was done before? Are you absolutely certain that they put in the newer style piston rings with extra clearance for the oil, etc? I've heard of a few people going to indy shops that just put new rings of the old version in and then drive for a few years before the problem comes back. Granted, MongoMcG may be doing you a huge service by bringing attention to the timing chain tensioner (skipping a tooth means goodbye car), so do make sure to check that out at the dealer. Lastly, at this mileage, I would start to think about parts of any car that can go wrong after a lot of miles, such as head gaskets, injectors, high-pressure fuel pump, etc. The injectors and hpfp can be tested very easily using vagcom or obd11 and looking the the fuel trim and pressure in the rail. Good luck!

[PuddlingNuts]

They replaced the PCV with the standard OEM version, not sure the code is ending with AH, I'll take a look.
I did the thorough engine repair in a shop with good reputation. Here are some pics ( before & after )

[redrackham17]

Yeah bro, in that case, I'd say you might have an issue with a piston ring again. Is there any pinging you notice? If that much oil is getting into the combustion chamber and on the spark plug electrode, I would expect the engine to ping like crazy under load or at low acceleration. I had that issue caused by injectors that were dripping fuel into the cylinder all the time, which burnt up the electrode and caused some serious pinging. Fixed it by replacing injectors and plugs. If it is indeed oil on your electrode, I'd say you have some type of a lower engine issue, like a piston ring, etc. Otherwise, if it's just dirty fuel that dripped into the cylinder, you might be okay after switching out the injectors. Keep us updated!

[Theiceman]

I have purposely said nothing in this thread as I wanted to give others a chance to weigh in and not bias opinion..
I would trust NOTHING that shop said or did regardless of reputation.

I'm just surprised no one said anything

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[PuddlingNuts]

Which revision of the PCV did you switch to? If your car was never updated to the white top, you should have put in one ending with park number "AH" because it's the newest blacktop revision. Switching to the upgraded white top requires work on the ecu and the front crank seal.

It's the AH version I guess, right? Part code 06H103495AH.

[PuddlingNuts]

Yeah bro, in that case, I'd say you might have an issue with a piston ring again. Is there any pinging you notice? If that much oil is getting into the combustion chamber and on the spark plug electrode, I would expect the engine to ping like crazy under load or at low acceleration. I had that issue caused by injectors that were dripping fuel into the cylinder all the time, which burnt up the electrode and caused some serious pinging. Fixed it by replacing injectors and plugs. If it is indeed oil on your electrode, I'd say you have some type of a lower engine issue, like a piston ring, etc. Otherwise, if it's just dirty fuel that dripped into the cylinder, you might be okay after switching out the injectors. Keep us updated!

Hey! Thanks for checking out the thread, no issues whatsoever while driving the car.
The misfire occur suddenly after driving long distances, today the technician confirmed it was an oil-related issue - an oily spark plug. I decided to change the oil & filters and drive it as it is as I cannot afford another engine rebuild at the moment.

I'm thinking to buy high-octane petrol, maybe the oil will burn better and will not deposit on the spark plug?
Also, maybe high revving from time to time to prevent misfiring? I have really few short-term options left...

[redrackham17]

You should be only putting 93 in the car tbh... If you already are, and by high octane, you mean even higher octane fuel consistently, you might get tired after a while doing that. Also, when you say the electrode has oil in it, do you mean literal liquid/sticky deposits of oil all over the plug and bottom of the coil and the spark plug well itself, or is it simply an indication of oil burning caused by dark soot on the electrode? If it's the former, you have a valve cover gasket leak causing the well to get flooded, or something else within the head. If it's the latter, you are burning oil, either through your rings or through your PCV and intake system malfunctioning. How is your carbon buildup on the valves? Have you checked down there recently?

Edit: Also, yeah. Seeing that your car is a 2009, you should have the updated blacktop AH. That is, unless your car was updated at the dealer with a new front crank seal and software to accept the white top.

[PuddlingNuts]

If it's the latter, you are burning oil, either through your rings or through your PCV and intake system malfunctioning. How is your carbon buildup on the valves? Have you checked down there recently?

The spark plug wells were dry last time I checked while having the issue - shaking engine, CEL and EPC on with no power. So it's either the upper valves or the rings. Either way, the cylinder head must be removed.
For now, I'll drive it as it is. And when a missfire will occur, I'll clean the spark plugs myself.

[Seal1968]

Do you have a VCDS to scan it? Your error "misfire cylinder 4" isn't very specific. There will be a code thrown. For CEL and EPC lack of power, you'd likely see error code P0341 for camshaft position sensor and the like, as your car may have gone into "limp mode" as it suspects a timing issue.

Have it scanned, otherwise you're guessing.

[Theiceman]

You should be only putting 93 in the car tbh... If you already are, and by high octane, you mean even higher octane fuel consistently, you might get tired after a while doing that. Also, when you say the electrode has oil in it, do you mean literal liquid/sticky deposits of oil all over the plug and bottom of the coil and the spark plug well itself, or is it simply an indication of oil burning caused by dark soot on the electrode? If it's the former, you have a valve cover gasket leak causing the well to get flooded, or something else within the head. If it's the latter, you are burning oil, either through your rings or through your PCV and intake system malfunctioning. How is your carbon buildup on the valves? Have you checked down there recently?

Edit: Also, yeah. Seeing that your car is a 2009, you should have the updated blacktop AH. That is, unless your car was updated at the dealer with a new front crank seal and software to accept the white top.

91

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[PuddlingNuts]

Today I got another misfire, after driving about 300 miles from the last service & oil change. I took the spark plug out, cleaned it with soap, and brush it until the metal was visible. The car drives well again.

Before

After


https://imgur.com/a/ohSGSwK

[PuddlingNuts]

Hi all, the engine finally died. It's shaking at idle and cleaning the spark plugs won't help. The car lasted 80k miles after the last engine rebuild when we changed pistons, rings, and connection rods. Now I'm looking to see if it is worth performing a second engine check & rebuild. Maybe this time, only the valves are faulty.

The downhill missfire was annoying for a while, but I managed to handle it by revving the car when driving downhill. Later, I started to get this error "Switch off engine and check oil level".
And weeks later, suddenly, the engine showed EPC light and shortly crashed - shaking, white smoke, etc.

[Theiceman]

so.... how did they replace the pistons without removing the engine ? as the RMS flange prevents you from removing the upper oil pan ?

[PuddlingNuts]

so.... how did they replace the pistons without removing the engine ? as the RMS flange prevents you from removing the upper oil pan ?

I'm not sure, the engine was partially detached from the body. The following pistons were installed: 06H 107 065 DD, PP 23.06.2015. Unfortunately, the oil consumption reappeared after 85.000 miles & 9 years. Mostly driving in the city.
#06H107065DD #CDNB #TFSI