2010 A4 B8 Misfire Issue

[Abu_boost]

Hey guys,

I have a 2010 a4 quattro. The car runs great as I'm driving but I have a issue that I just can't figure out. If my car is at idle, it reads a misfire for cylinder 3 and sometimes a random misfire. I've changed the spark plugs, coil packs, fuel injector, pcv valve, and looked for vacuum leaks. The issue isn't going away.

I've looked all over the forums and tried everything that I've seen..

Any ideas as to where I should look next?

[Prof]

Did you have your intake valves cleaned of carbon deposits? I had the same problem and after having the carbon deposits removed, the engine runs like new (2009 A4).

[Abu_boost]

Did you have your intake valves cleaned of carbon deposits? I had the same problem and after having the carbon deposits removed, the engine runs like new (2009 A4).

Ya, forgot to mention. Had the carbon cleaning done and a compression test done. All was good.

[STA4]

Perhaps an issue with valve guides: http://www.audizine.com/forum/showth...sue-In-Low-RPM

Can you describe how your car idles? Does the RPM fluctuate? Is the misfire very noticeable or just a shake?

[Abu_boost]

Perhaps an issue with valve guides: http://www.audizine.com/forum/showth...sue-In-Low-RPM

Can you describe how your car idles? Does the RPM fluctuate? Is the misfire very noticeable or just a shake?

If I start my car up first thing in the morning as the car is cold, I will have 0 issues. It's only when I start my car as it is already warmed up. Then the CEL will start flashing. If I put my car in drive as the CEL is flashing and let the car roll without giving it any gas, the flashing eventually stops and I can drive with no issue. If i give it gas as it starts flashing, the CEL turns on and I can still drive it with no issue.

The misfire isn't very noticeable, just a small shake at times. But i feel that same shake even when the car isn't reading a misfire.

The RPM fluctuates anywhere between just under 1k to 600 at idle when it is already warmed up.

[B8Nate]

If I start my car up first thing in the morning as the car is cold, I will have 0 issues. It's only when I start my car as it is already warmed up. Then the CEL will start flashing. If I put my car in drive as the CEL is flashing and let the car roll without giving it any gas, the flashing eventually stops and I can drive with no issue. If i give it gas as it starts flashing, the CEL turns on and I can still drive it with no issue.

The misfire isn't very noticeable, just a small shake at times. But i feel that same shake even when the car isn't reading a misfire.

The RPM fluctuates anywhere between just under 1k to 600 at idle when it is already warmed up.

Definitely sounds like carbon buildup, I just did this last week, removed my intake manifold and cleaned the 3 closed valves with b12 chemtool carb cleaner, and wire brushes I picked up from Lowes. Turned the crank manually from underside. Cleaned the last valve. Reinstalled everything. Turned it into a 2 day weekend project, since it's long process. Probably 4-6 hours. Depending how good you clean it / how dirty it is. My car has right at 60k miles and it was misfiring randomly cylinder 1 and 2. After cleaning it seems to idle much smoother and is running smoother when on the gas. for 60k miles I was shocked at just how dirty it was, not sure what your mileage is but that's def something to look at. Also coil packs, plugs and wires of course. But all of mine were new with less than 10k on them so I knew exactly what my problem was.

[B8Nate]

FYI -- used this DIY here, very simple with the instructions @Dan_Q explained everything GREAT! http://www.audizine.com/forum/showth...Valve-Cleaning like I said just be prepared the manifold is easy to get off with those instructions, but cleaning it does take some time, so be patient, grab a friend or 2 to help and talk to while doing it, worked about 2 hours a day saturday and sunday removed all of it and valves are back silver, everythings been running great ever since.

[B8Nate]

crap I just read that you had the cleaning done and compression test done, SORRY!!! I'm at work. Are coil packs, spark plugs and wires are good?

[Abu_boost]

crap I just read that you had the cleaning done and compression test done, SORRY!!! I'm at work. Are coil packs, spark plugs and wires are good?

Ya everything was done already. Still don't know where the problem is. Not sure what I'm missing at this point.

[Abu_boost]

Perhaps an issue with valve guides: http://www.audizine.com/forum/showth...sue-In-Low-RPM

Can you describe how your car idles? Does the RPM fluctuate? Is the misfire very noticeable or just a shake?

He just updated his thread, after all that work it turned out that wasn't the issue after all.

[B8Nate]

Ya everything was done already. Still don't know where the problem is. Not sure what I'm missing at this point.

sorry wish I could help, I legit drove off the audi lot and was having some issues within a week. I immediately regretted buying an audi until I figured out this was a normal and pretty easy fix. The dealer replaced coil packs, plugs and wires, it helped but a week or 2 later, happened again. Did the carbon build up diy clean and it's been fine ever since. So not sure what it could be seeing as how you've done all that.

also FREE BUMP, so somebody can help him.

[Townending]

Do you have a VAGCOM cable? It seems you've done all the basic fixes for misfires, but maybe some logging will tell you more.

You mentioned that your car fluctuates between 600-1000 rpm at idle when warm. My car jumps between 675-730 (Car sitting in park/neutral), but is normally always right around 700 at idle when the engine is warm. 600 seems way to low.

[van462]

I wonder if the MAF could cause this. On a cold start at idle the computer is in cold loop mode and using baseline maps. Once the coolant temp reading is high enough, the ECU switches from baseline maps to actual sensor readings and does adjustments. A quick test you could do is warm the car up to where you have the fluctuating idle, and shut it off. Unplug the MAF and restart the car. Without a MAF reading it will force the ECU back into using baseline maps again. If the idle is again smooth then you may have a MAF or sensor issue. If you do have a Vagcom or even an OBD reader see if you can see the fuel trim values.

Note: if you rev the engine with the MAF unplugged it will stumble a lot.

[Abu_boost]

Do you have a VAGCOM cable? It seems you've done all the basic fixes for misfires, but maybe some logging will tell you more.

You mentioned that your car fluctuates between 600-1000 rpm at idle when warm. My car jumps between 675-730 (Car sitting in park/neutral), but is normally always right around 700 at idle when the engine is warm. 600 seems way to low.

I'm waiting on my vagcom cable, just ordered it a few days ago

[Abu_boost]

I wonder if the MAF could cause this. On a cold start at idle the computer is in cold loop mode and using baseline maps. Once the coolant temp reading is high enough, the ECU switches from baseline maps to actual sensor readings and does adjustments. A quick test you could do is warm the car up to where you have the fluctuating idle, and shut it off. Unplug the MAF and restart the car. Without a MAF reading it will force the ECU back into using baseline maps again. If the idle is again smooth then you may have a MAF or sensor issue. If you do have a Vagcom or even an OBD reader see if you can see the fuel trim values.

Note: if you rev the engine with the MAF unplugged it will stumble a lot.

I actually tried changing the maf before.. As soon as I changed it, the car got stuck in limp mode.. I ended up swapping the old one back in and it was fine again

[Abu_boost]

So one thing I noticed was that it seems to depend where the car is currently idling. It still fluctuates between like 650-1000.. It seems to misfire as it is hovering around and not at a steady rpm

[Abu_boost]

UPDATE: I took my car to another Audi dealership. They are blaming it on a bad timing chain.. Audi won't change just the timing chain, they want to put in a whole new motor.......

[piotrowr]

the whole motor? are you covered?

[Abu_boost]

Not covered.. But I call bullshit on that one.. They just don't want to do all the labor for changing the timing chain

[talkinghamster]

correct me if im wrong but isnt the timing chain up front? cant be that big of a deal. you could always call an independent shop that works on audis and see what they say about the chain.

my car did the same thing as yours and the problem was that it spun some sort of crank bearing. que a $2000 fix (add another 2000$ for replacing all four injectors and carbon clean) and its fine.... although i am not happy about that lol

[Abu_boost]

In my opinion the job is doable, so I'm gonna have it done. You just have to take off the entire front end.

[Dub_prime]

In my opinion the job is doable, so I'm gonna have it done. You just have to take off the entire front end.

There's a service position for the front end that allows access to all the belts.

[S4'ed]

The lower timing chain tensioner is problematic on the 2.0T. It often fails to tension the chain quickly enough when the engine is started, causing the timing chain to skip a few teeth (best case, engine will still run, but poorly), or a lot of teeth (then causes a piston to hit an open valve), causing $5000 worth of damage to the engine. VW/Audi came up with a revised design of the tensioner in late 2013 (engine build dates).

Could also be a head-gasket issue : Is your coolant level slowly dropping?

And of course the usual "suspect causes "
Coil pack
Spark plug
Injector
air leak at idle, causes a misfire due to a lean fuel-air ratio. On the 2.0T these are often PCV issues, or failures of the Rear Main Seal which causes an air-leak.

[Abu_boost]

Actually my coolant level does slowly drop. I noticed that at my last oil change, but it is very slow.

The pcv was already changed.

The thing I find weird is that it only misfires if the car is started up when it's already warm, but the car doesn't feel any different. You just see the blinking check engine light.

[Abu_boost]

The lower timing chain tensioner is problematic on the 2.0T. It often fails to tension the chain quickly enough when the engine is started, causing the timing chain to skip a few teeth (best case, engine will still run, but poorly), or a lot of teeth (then causes a piston to hit an open valve), causing $5000 worth of damage to the engine. VW/Audi came up with a revised design of the tensioner in late 2013 (engine build dates).

Could also be a head-gasket issue : Is your coolant level slowly dropping?

And of course the usual "suspect causes "
Coil pack
Spark plug
Injector
air leak at idle, causes a misfire due to a lean fuel-air ratio. On the 2.0T these are often PCV issues, or failures of the Rear Main Seal which causes an air-leak.

Is there anyway to check if the rear main seal is bad?

I'm having the timing chain done soon, along with head gasket all at once.