Rough acceleration continues - odd misfire "rumble/vibration" - but more power.

A6 All/ S6 All
#1

Hey guys,

So I’ve made some progress. Used my vagcom and pulled codes. Found that 4 cyls were misfiring badly, pulled those plugs and all were detonated white. Replaced plugs, used dielectric grease on the plug end + in the coil for better connectivity (why not). With those plugs swapped it’s running MUCH better.

I’ve got good power up on the high end now whereas before I couldn’t go half throttle up hill without a flashing CEL. Took it out for a 300 mile trip the other day, many WOT gear changes and full pulls. Nothing I could do before without that flashing CEL.

Lower RPM 2-4k I’m getting what feels like a bad misfire, but also like a warped or unbalanced driveline of some kind. It’s hard to explain (like a rumble/misfire) but it feels more prevalent in that lower RPM range and seems to disappear as revolutions pick up higher up int he RPM band around 4,500 to redline. Plenty of power up top.

Since the plugs were detonated, they were obviously getting spark but not enough fuel. Would a weak fuel injector cause misfires like this under less demand/load at lower RPM causing misfires but smooth out under higher demand near redline with more fuel being pushed? That being said, no new codes have come up.

No CEL since clearing codes and driving for the last few days, which makes more troubleshooting difficult. I’ll re scan later today after more driving.

Any thoughts?

PS - I’ve run a few cans of seafoam through the tank and done one intake treatment over the last couple weeks.

#2

I would say this to everyone. Its maybe not a bad idea to just make a build thread on here and update it with codes from the car when they pop up. After you clear the codes there gone if you put the codes on here they are here for all of us to see and help you with even after you fixed the car. And old codes are still imporntant to any current issue.

Generally the rule of thumb. low rpm missfire can be carbon plugs or packs. Higher RPM missifres tend to lean in the direction of fuel related stuff like injectors and filter.

That is a general rule but not exclusive. If you got mid range issues now it could be related to the coil packs being weak. See if you have a plug that goes bad it can cause more stress on the coil pack or the coil pack could have been the reason the plug fouled out or wasnt getting a good burn in the first place.

If your not getting the flashing CEL on the dash thats at least saying its probably not a missfire. Is there any chance that in changing the plug that maybe you have something that didnt get put back on right and its causing some rough running.

#3

Justincredible,

Sorry for the long delay… got sidetracked by some work.

I’ll keep any further back and forth to this thread, sorry for not doing so in the first place.

After a couple weeks with no CEL (but experiencing the rough feeling as described in my last post) I finally got a CEL that popped on after coming to a stop at an offramp on the highway. Car began to stumble a bit. Made it to a grocery store, came back out 30 min later, and it seemed just fine, but still with the same rough symptoms as before on throttle.

Just pulled codes - pulling coils/plugs for inspection. Will be replacing plugs and using dielectric grease this time around between the plug and the coil. Seemed to help this last time.

1 Fault Found:
006435 - Please Check DTC Memory of ECU Number 2
P1923 - 008 -
Freeze Frame:
Fault Status: 01101000
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 166250 km
Time Indication: 0
Date: 2016.05.18
Time: 15:12:09

         Freeze Frame:
                RPM: 0 /min
                Load: 0.0 %
                Speed: 0.0 km/h
                Temperature: 12.0°C
                Temperature: 18.0°C
                Absolute Pres.: 970.0 mbar
                Voltage: 11.811 V

6 Faults Found:
000768 - Random/Multiple Cylinder Misfire Detected
P0300 - 001 - - MIL ON
Freeze Frame:
Fault Status: 11100001
Fault Priority: 0
Fault Frequency: 2
Reset counter: 255
Mileage: 164458 km
Time Indication: 0
Date: 2016.04.26
Time: 14:47:59

         Freeze Frame:
                RPM: 563 /min
                Load: 23.5 %
                Speed: 0.0 km/h
                Temperature: 93.0°C
                Temperature: 18.0°C
                Absolute Pres.: 990.0 mbar
                Voltage: 14.351 V

000775 - Cylinder 7
P0307 - 008 - Misfire Detected - Intermittent
Freeze Frame:
Fault Status: 00101000
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 164458 km
Time Indication: 0
Date: 2016.04.26
Time: 14:47:59

         Freeze Frame:
                RPM: 563 /min
                Load: 23.5 %
                Speed: 0.0 km/h
                Temperature: 93.0°C
                Temperature: 18.0°C
                Absolute Pres.: 990.0 mbar
                Voltage: 14.351 V

000771 - Cylinder 3
P0303 - 008 - Misfire Detected - Intermittent
Freeze Frame:
Fault Status: 00101000
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 164458 km
Time Indication: 0
Date: 2016.04.26
Time: 14:47:59

         Freeze Frame:
                RPM: 563 /min
                Load: 23.5 %
                Speed: 0.0 km/h
                Temperature: 93.0°C
                Temperature: 18.0°C
                Absolute Pres.: 990.0 mbar
                Voltage: 14.351 V

000776 - Cylinder 8
P0308 - 008 - Misfire Detected - Intermittent
Freeze Frame:
Fault Status: 00101000
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 164458 km
Time Indication: 0
Date: 2016.04.26
Time: 14:47:59

         Freeze Frame:
                RPM: 563 /min
                Load: 23.5 %
                Speed: 0.0 km/h
                Temperature: 93.0°C
                Temperature: 18.0°C
                Absolute Pres.: 990.0 mbar
                Voltage: 14.351 V

000769 - Cylinder 1
P0301 - 001 - Misfire Detected - MIL ON
Freeze Frame:
Fault Status: 11100001
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 165954 km
Time Indication: 0
Date: 2016.05.15
Time: 00:00:36

         Freeze Frame:
                RPM: 4019 /min
                Load: 78.0 %
                Speed: 59.0 km/h
                Temperature: 95.0°C
                Temperature: 17.0°C
                Absolute Pres.: 970.0 mbar
                Voltage: 13.589 V

000774 - Cylinder 6
P0306 - 001 - Misfire Detected
Freeze Frame:
Fault Status: 01100001
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 166214 km
Time Indication: 0
Date: 2016.05.16
Time: 16:35:01

         Freeze Frame:
                RPM: 2604 /min
                Load: 17.2 %
                Speed: 120.0 km/h
                Temperature: 93.0°C
                Temperature: 15.0°C
                Absolute Pres.: 980.0 mbar
                Voltage: 14.097 V
#4

Those codes are interesting after looking at the freeze frame data.

  1. It looks like you are getting warm start/idle misfires on cylinders 3,7, and 8.

  2. Then there is a high load/mid range rpms misfire on cylinder 1.

  3. Finally it looks like a deceleration misfire on cylinder 6.

That kind of inconsistent freeze frame data stored for misfires along with the spark plugs looking like you described would lead me to believe that your injectors are not working correctly. Some injectors could be leaking down with warm starts on short trips. Others could not flowing correctly under load.

#5

Flow check injectors? How many miles they can go in as little as 40-50k on these cars

#6

Thanks, guys.

I’ve been suspecting the injectors as well after confirming all but cyl 1 plug that was removed had been detonated white. Assuming this means they are all getting spark but not enough fuel.

I replaced the plugs on problem cyl in my previous vagcom scan. The misfire/vibration issue had subsided greatly, though after a bit of driving it’s still present on a less pronounced scale. If it’s fuel related, wouldn’t changing the plugs not have an effect on the misfire issue (unless they are burned up)? It seems new plugs smooth things out greatly.

I should note I’ve gotten some surging under WOT approaching redline in 2nd and 3rd gear. Symptom of weak injectors under demand?

I don’t have a CEL at the moment, however I’ll pull codes to see if any smaller misfires have been recorded. I’ve got a lead on injectors from a supplier for about $65 each, which is a steal (hitatchi) - so it may be in my intrest to replace them all in one go after removing the intake manifold.

I’ll post new codes asap.

Thanks for the help!

#7

That’s interesting. These cars are pretty finicky if not running right meaning the check engine light comes on pretty easily. Wth that said some misfires could be possible and not trigger a cel. What have you done maint wise recently? Done a 60k or what else have you replaced?

#8

got the car back in september 2015 - had a bad oil separator at the car dealer being sold at. After waiting a couple days without their mechanic doing the work, I requested the local Audi dealer take it in for repair. Car was given a clean bill of health before I signed papers to take it home. CEL came on while driving back from IN to VT.

Replaced all coils and plugs shortly after returning home with it. Ran well until November, Flashing CEL on throttle. Replaced select plugs, ran better, still not as well as the day I got it. Had carbon cleaning done thereafter, had more power but slowly misfires got worse, Flashing CEL.

Recently replaced the plugs mentioned in my last post, and I’m back to smoother driving but not 100%.

No other major services have been done since in my possession. I went over records with the dealer and they said it had a great history, always in for every milestone service until 95k when sold. I’m at 120k or so now.

Being that I’ve replaced all coils and plugs (multiple times) I’m thinking injectors are the culprit at this point?

#9

Higher RPM missfires are usually injector related.
Lower rpm are usually vac leaks
mid range rpm missfires are generally plugs and packs

White plugs usually mean no fuel or lean

I wouldnt get new injectors you learn nothing and you might just be burning your money. Get your injectors cleaned. That is the absolutly best thing you can do. It costs about half or less and you can get some idea on if there was an actual injector issue in the first place.

Do we have an injector thread here. This is a big thing with the RS4 guys. I cant suggest enough that you dont get new injectors even if you get new injectors you would want to have them tested. new injectors can flow way less and some flow way more.

If you have your injectors cleaned you also get them flow matched so each cylinder is getting the exact same amount of fuel and when they are cleaned and rebuilt they are just as good.

#10

Yes. Clean, flow match :slight_smile: based on what I’m hearing described this is best course of business

#11

Just incredible, agrees. thank you.

I believe my local dealer has a cleaner/flow tester. A friend works in sales and may be able to help me out. Off with the intake manifold it is. I’ve yet to do this, but I know the forum has documentation to follow.

After fixing vac leaks, changing coils and plugs, injectors are the logical next step.

Ps car is only at 103k not 120k; not sure what I was thinking.

Appreciate the help and will report back after injectors are inspected, tested and re installed.

#12

Please let us know. the injector cleaneing is the way to go much better for you.

There is a link to pulling the intake off and the carbon clean. Its in this section

#13

I’m getting the same problem right now: very rough idle on cold start with misfires on cyl 4 & 9. Worst when I’m just pulling out of parking space. Sometimes it seems to settle down and run just a little rough at driving speeds. Other times it doesn’t.

I read the RS4 post on injector flow testing, but I’m not sure if I can find a local shop with an ASNU machine. Lacking that, is the next best option just replacing injectors on 4 & 9 to see if that fixes things?

Changed all the plugs and coil packs last week

#14

It’s worth a try, I think.

My car started displaying very similar symptoms right around the same time I got a Cylinder 4 misfire light. Rough while backing out of a parking space, and for the first 100ft or so of driving. Strange feeling, it was almost like I was getting bursts of power even while I didn’t have my foot on the gas. JHM reports that plugs, injectors, and coil packs were all overdue for replacement. Since you’ve done 2/3 of that already, I think it’s worth a try replacing those 2 injectors.

#15

Cold start missfires can be from the SAI system. If your getting the codes or missfires while your driving that is something else to look into. If you have over 300 miles on the car since the last code clear and you dont have any other codes then its a good idea to look at the injectors. You can just swap the injectors from one side of the motor to the other side. This is quicker and will help telll you if its an injector issue or not.

#16

I’m also getting the misfires during normal driving (flashing MIL). Today it was very rough on cold start, and still rough after it warmed up.

Plus, I got a throttle fault, P1579 & P0221, which I thought might be due to walking out of the car with the key in my pocket while warming up(?). I restarted the car and the throttle was seemed fine again, but all these lights are making me wonder.

What does that mean?

#17

Do you have the vag com data or just the P codes. I will have to look up those p codes because I dont know what they are off hand.

#18

I only have P codes for now. My mechanic comes back from Zagreb near the end of the month. I’ll have vagcom then.

#19

Get the codes and freeze frame codes. The freeze frame codes will get you rpm load and other detials that lets you know when the issue happened.