# Cylinder 3 misfire



## vwlippy (Jul 17, 2001)

Here we go again. Cylinder 3 misfire showed yesterday.
It's been 58k miles since I last changed the plugs and about 42k miles since my coil packs were replaced for free by Audi. 

Should I just get new plugs OR plugs and coils OR plugs and just replace cylinder 3 coil pack. 

I know it could be something else, but one of these two seems most likely. 
Thoughts?


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## VRooom6 (Oct 18, 2007)

Does it misfire only when it's cold and then stops when the car heats up?
If yes, 99.9% carbon build-up...did mine a week ago and maaaan, day and night!!!


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## vwlippy (Jul 17, 2001)

Do you mean carbon build up on the valves or the plugs?


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## VRooom6 (Oct 18, 2007)

Carbon build-up on the intake valves...
Like I said, my A3 has 63000 miles on it and the intake valves were gross. The car started misfiring on cold starts and would jerk and misfire as long as it did non heat up completely. It would be more noticeable on low rpm's and constant gas pedal pressure (keeping rpm's at 1500 in 2nd, 3rd or 4th gear). I changed the plugs since I was due anyway, and also changed my ignition coil on cylinder 3 (since I also had a misfire on cylinder 3) and it remained the same.
Afterwards, I took off the intake manifold and cleaned the intake valves with carb cleaner. KABOOM, night and day!!! I was starting to find that my car was lacking power compared to before, I swear only intake valve cleaning must have given me back like 30-40 hp that were stolen from me .

BTW this is a nice writeup on how to clean the intake valves:
http://forums.vwvortex.com/showthread.php?5355100-TSI-Intake-Manifold-Removal-DIY-Valve-Cleaning

ps. The thread above is for a TFSI engine but I'm pretty sure you can find one for a FSI


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## VWAddict (Jun 12, 1999)

First thing I thought of when I read the title was "I wouldn't bet against carbon!"

Easy (and without throwing money at random parts speculatively) test for plugs/coil packs is to swap them... -say swap 1 and 3, also swap 2 and 4.

If it was a coil pack or plug, the misfire would move to 1.

If it stays with 3, then I'd put money down on carbon.


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## neu318 (Feb 18, 2003)

I know it's a whole different car but when I had my MKIV gti coil packs never lasted that long. A bunch of people always kept a spare coilpack in the trunk. I also had a misfire issue with a certain brand of gas. As stated above, move the coilpack to a different cylinder to see if the misfire moves. If it does then it's your coilpack.


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## rad_rob (Mar 6, 2013)

I had a very similar problem last week. I have a buddy who works at the local Audi dealer and took it over to him. Turns out the intake manifold flap position sensor failed. Unfortunately requires a whole new intake manifold, which actually wasn't too expensive. While he was installing it, he showed me how insanely disgusting the valves were (person who owned the car before me ran nothing but ****ty gas) so he cleaned them while he was in there. Now that the new sensor was working properly, along with the freshly cleaned valves made a HUGE difference. So as already stated, it could be the valves. If that doesn't fix it, check that flap position sensor too. That was what caused my initial CEL.


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## TBomb (Sep 23, 2009)

rad_rob said:


> I had a very similar problem last week. I have a buddy who works at the local Audi dealer and took it over to him. Turns out the intake manifold flap position sensor failed. Unfortunately requires a whole new intake manifold, which actually wasn't too expensive. While he was installing it, he showed me how insanely disgusting the valves were (person who owned the car before me ran nothing but ****ty gas) so he cleaned them while he was in there. Now that the new sensor was working properly, along with the freshly cleaned valves made a HUGE difference. So as already stated, it could be the valves. If that doesn't fix it, check that flap position sensor too. That was what caused my initial CEL.


Couple things here.

1. The 2.0T FSI/TSI are direct injection engines, so it doesn't matter what kind of fuel you run, it never touches the valves and thus has no impact on carbon buildup. There are 100's of theories as to what causes the issue, and equally as many "solutions"...the only one that works is pulling the intake manifold and manually scrubbing the valves every so often. This is the case across almost all direct injection engines that do not use an auxiliary fuel injector specifically to spray fuel on the valves to keep them clean.

2. If the IMRC fails, you will typically have a solid MIL set. When mine failed I did not notice any driveability issues. Obviously that's not always the case, but...

3. Misfires almost always result in a blinking MIL, not a solid one. That's an easy way to tell. Blinking MIL = bad news bears.

4. Like Keef already mentioned, swap your #3 coilpack with, say your #1 coilpack and see if the misfire follows. If it does not, then put the coilpacks back but swap your #3 spark plug with your #1 spark plug. If it still doesn't, then I'd swap the coilpacks back so that you're now running your #3 plug and coilpack in the #1 cylinder and vice versa, just to rule out all combinations. If that is inconclusive, then I would pull the intake manifold, clean the valves, and inspect the fuel injectors. :thumbup:


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## vwlippy (Jul 17, 2001)

Ok, sounds good. I'm going to swap the coils first and see if the code jumps, then test the plugs, etc. 
... anyone have a diagram of the cylinder order?


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## neu318 (Feb 18, 2003)

vwlippy said:


> Ok, sounds good. I'm going to swap the coils first and see if the code jumps, then test the plugs, etc.
> ... anyone have a diagram of the cylinder order?


If i'm not mistaken the one closest to the passenger side is cylinder 1 and then follows 2,3,4 etc...


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## VWAddict (Jun 12, 1999)

That's correct; the one nearest the accessories belt is number one, the one nearest the transmission is number 4.

-Not that it matters, if you're swapping 1-3 and 4-2, it's still the same no matter which way you count it: -Outer-left swaps with inner-right, and outer-right swaps with inner-left.

Don't forget to reset the code when you do the swap :thumbup:

While the fuel does indeed NOT wash the back of the vales, I would caution that it's a specious argument to then say that the fuel cannot therefore make a difference... -For hypothetical example, if one brand of fuel burned without producing ANY carbon soot, there would be none produced to wash off, so I'm not convinced by this observation alone...

Even though I'm leaning slightly toward the 'the fuel may all be the same' argument My jury is currently out.


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## TBomb (Sep 23, 2009)

VWAddict said:


> That's correct; the one nearest the accessories belt is number one, the one nearest the transmission is number 4.
> 
> -Not that it matters, if you're swapping 1-3 and 4-2, it's still the same no matter which way you count it: -Outer-left swaps with inner-right, and outer-right swaps with inner-left.
> 
> ...


How do exhaust gasses get returned to the intake valves, then? Is there significant enough valve overlap to allow exhaust gas to escape from the combustion chamber and create deposits on the entire intake valve, not just the backs or any one side, as well as the intake port and the port dividers? Color me skeptical.


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## VWAddict (Jun 12, 1999)

TBomb said:


> How do exhaust gasses get returned to the intake valves, then? Is there significant enough valve overlap to allow exhaust gas to escape from the combustion chamber and create deposits on the entire intake valve, not just the backs or any one side, as well as the intake port and the port dividers? Color me skeptical.


I'm not claiming to know.

But if the soot is NOT coming from the car, where else would it be coming from? -It doesn't seem to be fouling the engine air filter.


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## forma (Nov 22, 2005)

with regards to carbon buildup, you can try "italian tune up"


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## vwlippy (Jul 17, 2001)

Ok, coils 1 and 3 swapped and code cleared with my new toy
http://actron.com/uscan/
Actron U-scan that works with your iPhone. 

We'll see what code it throws tomorrow on my way to work


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## MisterJJ (Jul 28, 2005)

Not to beat a dead horse, but... aw hell, beating a dead horse is what we do best around here.

Yes, there is some valve overlap, but not enough to cause the problem over such a large area.

The PCV system takes a mixture of oil, water, fuel (piston blow-by), and combustion byproducts and dumps it into the intake manifold. People with catch cans have proven that removing this component has little or no effect. I theorize that the fuel being removed with a catch can is preventing it from slightly cleaning the valves, cancelling out the effects of removing the bad stuff.

This leaves the well documented "weeping" of the valve guides. The oil drips down the valve, which is traveling rapidly up and down, and splatters around the area where it gets baked on.


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## vwlippy (Jul 17, 2001)

UPDATE: 
I switched the 1 and 3 coilpack. The light came back on yesterday and still showed a Cylinder 3 misfire. So, I swapped the 1 and 3 sparkplug this time. I hope this switches the misfire to Cylinder 1, but I have a bad feeling its not going to.


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## everfresh59 (Jul 26, 2010)

forma said:


> with regards to carbon buildup, you can try "italian tune up"


Always fun to do!! Justifiable excuse to go woot!


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