Ongoing Misfire Cyl 3

B8 S4
#1

Hoping some expert advice comes my way and helps me get this sorted;

Car - 2013 S4 GIAC Stage 2 + DSG
Gas - 93 oct, never had anything less. Have put in 100 oct in the past to run the race file but not as of recently.

Prior to this episode I have only had 1 misfire and that was in hot weather on the track at around 30k miles. Only had EPC light come on, limp mode. Turned car off and back on and all was well.

Changed all my plugs roughly three months ago to these when I hit 55k miles:

http://www.amazon.com/gp/product/B001B6VUTM?psc=1&redirect=true&ref_=oh_aui_detailpage_o06_s02

Gapped all to .32 (most were right there from the box). Not an OEM direct replacement but was to have been a step up, others have used with out any issue. In addition I am only having issues on cyl 3, I figured if it was a poor plug I would see issues on the other cylinders.

Roughly 30 days later misfire cyl 3 (EPC light and Limp mode) I don’t remember my driving conditions for this one.

Pulled the plugs, checked them and all seemed fine, put them all back in. Two weeks later misfire again on cyl 3, turned car off and back on to clear. Was driving around 2800RPM. A few days later when downshifting at a light (DSG Manual mode) from 3rd to 2nd (peak rpm of around 4200 on the downshift) the EPC light comes back on and limp mode. Turn car off, turn back on and all is well.

Picked up a spare plug, put it in cyl 3 and continued on thinking maybe I had a bad plug. Driving on the highway, S mode 6th gear, 3200rpm…EPC light comes on and limp mode. Turn car off and back on, drive for a few hundred miles and again I go into limp mode but this time throws the engine light on (all other times was just the EPC light).

Turn car off, back on, drive the remaining 500 miles home no issues. Pull the codes, again cyl 3 misfire.

Thinking at this point its the coil pack, I replace it. No issues for a solid month (daily driving, hard driving, etc).

Last week driving around 35mph in D mode and it throws the EPC light and I go into limp mode.

Ive not had any issues on any other cylinders. I have replaced the plug on cyl 3 as well as a new coil pack and swapped coil packs between cyl 3 and 4.

Not sure where to go after all this, only other guess is that its an injector issue. Looked for directions on how to find out if that is the problem (pulling them or logging via Vagcom) and haven’t come up with anything.

Thanks for reading and hope to figure this out.

-AZ

#2

Image of cyl 3 plug pulled after 1500-2000 miles

http://i.imgur.com/jKK5xXw.jpg

#3

Yup could be an injector seal. That would be the same code you are seeing and you did rule out cp and sp. Would hurt to shine a light in that cylinder to make sure it looks OK too but let’s not go there yet :slight_smile:

Mike

#4

Replace the coil pack?

#5

Did that with a new one as well as swapping them around.

Anyone find a post on how to get to the injectors…did some serious googling and can’t find anything on it.

#6

did your car have the fuel rail recall? i know they are swapping out rails and seals.

#7

I thought that recall only affected 2011-2012?

#8

In my case, same symptoms, after much investigation it was found to be a bad reluctor ring, maybe mine was damaged when they swapped the motor in my car previously. I had no other codes, but I kept taking it back to the dealer until they figured it out, since it was warrantied still.

#9

Would the reluctor ring changed be on the distributor or crankshaft…? They’re on the ABS
System as well. I take it that it should be on one of the previous two smog it has to do with timing.

#10

OT: db, I think I may have spotted you out on the road Thursday night. I was out golfing in West Chicago and headed back downtown around 8:30pm. Were you out in that area?

#11

yep that was me! :slight_smile:

#12

Onto google to see what the hell a reluctor ring is and how I can replace it…

#13

Looks as if this part is in the shaft…not sure that will be my issue

#14

No, this is the reluctor ring for the crankshaft position sensor, that is typically on the drive plate/flywheel assembly in most Audis…although I have to assume it looks the same on the DSG B8 S4, never separated the engine/trans and pretty unlikely I’ll ever do this one myself to see it.

It’s unlikely to be damaged on your car unless your motor/trans has been separated.

I’d just keep taking it to the dealer to diagnose…it took 5 tries to finally get them to spend a couple months with the car to finally figure it out. Assuming you still have warranty.

#15

chances are if it was the damaged ring you would be getting codes on more then one cylinder. Getting faults on high load situations would lean in the direction of the injector. You already changed the coils and plugs. You can go into vag com and do an injector test in the motor section and output test. On a FSI car I don’t know if the car has to be on.

I know with the blower on the car this would be a lot of work but I would move the injector first and see if it follows

#16

Will dig in with VC and see if I can figure it out (and if I can, post up here for future step by step).

Thanks for the suggestion.

#17

I thought so too, but no codes would show up except the EPC and misfire on the same cylinder. Makes sense if the ring was damaged in one spot. But unless he’s had the engine and trans separated, it’s unlikely he has a problem with the ring. It’s just interesting he had the same symptoms.

The dealer on my end swapped the Mechatronics and the ECU, finally before tearing it apart again and replacing the ring. I didn’t bother asking how they got to any of those conclusions, got a lot of seat time in various loaner Audis, but it’s been no problems for 40,000 km since then.

#18

Soo…who would have thought it was this:

http://images.tapatalk-cdn.com/15/07/20/d52d0effc14f5cfce238c21ff2e2f04d.jpg

Leaking cooler into cyl3, it was the tiniest leak. Too hard to repair new part on its way.

http://images.tapatalk-cdn.com/15/07/20/1aefcfcc563e53a9da094503fbe7e0bf.jpg

http://images.tapatalk-cdn.com/15/07/20/ac4125da2416258dee8f2debfd4b4fad.jpg

#19

Weird…What would cause damage to the ic like that? Impressive that you tracked it down, especially given the coincidence of replacing the plugs.

#20

Well that sucks but good find like drob said… Would have never guessed it… Glad to you got it figured out and thanks for sharing…