Misfire moving around - help with proper diagnosis

Any help is greatly appreciated:
Recently had misfire on cyl 8. Replaced all spark plugs, moved cyl 8 ignition coil to cyl 3 and drove fine for several hundred miles. Cyl 3 threw a misfire code, and in process of pulling ignition coil to swap with new one the coolant elbow snapped and needed replacing. Replaced coolant elbow and ignition coil and started up, now misfires on multiple cylinders. Continues to move with testing through moving ignition coils and replacing spark plugs. Disconnected and re-seated injectors. Compression test is fine when wet testing cyl 3, otherwise cyl 3 is low by 50psi (no oil dropped in cyl, cold). Continued testing is coming up with just more randomness, now misfires are just on bank 1.

Also posted on audizine (I hope its ok to post links?): https://www.audizine.com/forum/showthread.php/818138-Misfire-spreading-help-with-proper-diagnosis?p=13239790

Full story, bulleted
Trying to diagnose a moving misfire. Have done initial troubleshooting and am at checking injectors with Vag-Com and could use a little help

2 years ago (10K mi) I had a misfire on cylinder 2 - replaced plugs (all looked pretty bad at 10K) and replaced the 1 ignition coil for that cylinder B7 S4 Spark Plugs - 11.16.16

The latest, from when I had a cylinder 8 misfire originally, earlier this month:

  1. Pulled all spark plugs, replaced with new (10k on these plugs - looked OK but not great: B7 S4 Spark Plugs - 6.07.18)
  2. Compression test showed cylinder 3 has bad rings - low compression until adding a little oil to cylinder, was fine after oil
  3. Swapped cylinder 8 (misfiring) ignition coil with cylinder 3 ignition coil
  4. Ran fine for several hundred miles until last Sunday when I got a bad misfire on cylinder 3
  5. Began making access to bank 1 to replace cylinder 3 ignition coil and the coolant elbow snapped B7 S4 - Misfire Diagnosis - Coolant Day
  6. Replaced coolant elbow with aluminum elbow
  7. Replaced ignition coil on cylinder 3 with new coil
  8. Added coolant to reservoir and started up. Ran rough as hell, turned off. Cleared codes (showed multiple misfire on first startup, just like when I swapped the new plugs in and moved the ignition coil and started it up first time. After clearing the codes that time, it ran fine with no codes)
  9. Started up again, rough as hell, showing misfire of cylinder 3 again. New coil, plugs have 300 miles.
  10. Checked all connections, including injector and nothing looks/feels out of place
  11. Re-installed the new ignition coil on cylinder 3 just to be sure - started up and still rough.
  12. Moved new ignition coil from cylinder 3 to cylinder 4 (and vice versa) and started up - misfire spread to now cylinders 3 and 4
  13. Moved all ignition coils around:
    cylinder 1 to cylinder 8
    cylinder 2 to cylinder 5
    cylinder 3 (new) to cylinder 7
    cylinder 4 (original) to cylinder 6
    cylinder 5 to cylinder 1
    cylinder 6 to cylinder 4
    cylinder 7 to cylinder 3
    cylinder 8 to cylinder 2
  14. Misfiring spread again, now misfiring on cylinders 3, 4, and 7
  15. Swapped cylinder 7 (new ignition coil) back to cylinder 3 (originally misfiring cylinder, suspected bad ignition coil)
  16. Swapped in new (used but good condition) spark plugs to cylinders 3 and 4
  17. Cylinder 7 misfire is gone and cylinders 3 and 4 are still misfiring
  18. Cleared codes, re-ran with logging. Instead of misfires on 3 and 4 like I was expecting, I am now getting faults for misfire on 1, 3, 5, and 6 so it’s no longer isolated to bank 1 and really is jumping around. The current ignition coil in cylinder 5 is new as of 2016, or roughly 10K miles ago.
  19. Torqued intake manifold bolts, some had a good half turn or more in them. Bolted everything back up, fresh gas (was close to empty when this misfire on cyl 3 happened)
  20. Reset ECU by disconnecting both battery terminal leads and touching them together via a jumper cable, left battery unplugged overnight to drain capacitors. Cleared engine codes via VagCom. TB reset via VagCom.
    Started up right away and with a better idle than before but still misfiring:
    Cyl 1 Cyl 2 Cyl 3 Cyl 4 Cyl 5 Cyl 6 Cyl 7 Cyl 8
    0 0 4090 195 840 0 518 0
  21. Swapped ignitions coils: 1/3 and 5/6, cleared ALL DTC codes (had intermittent code issues related to battery drain, I presume - see earlier log above)
    Misfire codes came back on cylinders 1, 3, 4 but my misfire count log didn’t save correctly and then the battery and my instant start charger both got a little too weak to keep testing so they’re re-charging (car on Battery Tender Plus)

Next Steps?
I’m thinking I need to order injectors to test there but I had read somewhere there is an output test for firing each injector individually. Anyone know what group it is?
I’m also double checking the vacuum line connections best I can, based on these pictures/diagrams: https://www.audizine.com/forum/showt...outing-Diagram

Battery charged. Did two runs but only got misfire counts on the last.
First run the misfire codes came back on Cylinders: 3, 1, 5, 2, 8
Cleared codes, re-ran and got misfires on Cylinders: 1, 3, 4 (like yesterday) but with the following misfire counts (~45sec run time, low RPM rev and hold for several seconds):

[td]Cyl 1[/td]
[td]Cyl 2[/td]
[td]Cyl 3[/td]
[td]Cyl 4[/td]
[td]Cyl 5[/td]
[td]Cyl 6[/td]
[td]Cyl 7[/td]
[td]Cyl 8[/td]
Needless to say I’m even more confused now. Any direction would be really appreciated!

You might want to log your fuel pressure.


welcome to the forum. I would almost guarantee you will find the answer here. Most of the educated people left audizine and its drama long ago. Some of them are here.

So A few questions.

do you still have your pre cats in?
What are the cars LTFT after your able to drive for a short while.
How old are all of the coil packs from oldest to newest.
Have you looked inside your intake manifold to make sure the flap screws are still there.

Lets start with that and I’m quite certain we will be able to help you sort this out.

Thanks a bunch for the assistance - you are a legend among the Audi forums and have been a lot of help on other threads I’ve looked at, so thanks.

We’ve been recently hit with some health issues making it hard for me to find time to work on the car, so bear with me on the slow updates. I really do appreciate any and all help.

  • Have had JHM piggies installed for last 20K miles

  • Regarding driving while it’s misfiring this bad - it wants to start dying after a little bit of run time. I haven’t tried driving any distance, just idling. What is OK to do and what should I avoid to not risk further damage? I’m a bit of a newb when it comes to diagnosis and apprehensive of anything that might cause more things to go wrong. I am better at simply following directions from DIYs!
    On Audizine it was also recommended to get some readings while the car is warm. Again, just hesitant until someone with actual knowledge assures me!

  • Coils as far as I know:
    Cylinder 3 (bad rings by compression test) ignition coil was replaced during pre-purchase inspection (~25K miles ago)
    Cylinder 2 ignition coil was replaced ~10K miles ago on single cyl misfire code. All spark plugs replaced at this time.
    Cylinder 8 ignition coil was swapped with cylinder 3 ignition coil ~500mi ago on single cyl misfire code. All spark plugs replaced at this time. Swapped coils instead of replace to test if coil was bad or not.
    Cylinder 3 misfire code happened most recently so I began work on swapping the coil. This is the ignition coil that was previously on cylinder 8 that misfired 250mi prior. Car was low on fuel at this point, en route to gas station. While working on it the coolant elbow near cyl 1 broke and spewed hot coolant everywhere. I replaced elbow and ignition coil, added coolant, started up and got the range of misfire codes noted above.

  • I’m guessing I’ll need to take off the intake manifold to check the flap screws? Did a search and wasn’t finding much that addressed this.


That was very nice of you to say. I try to help. What we usually tell people on here is if we helped you help someone on AZ that needs real help that isn’t a troll and tell them to come here.

Now back to you.

If the car is hard missfireing don’t try to do anything with the car warm. That is just a recipe for disaster until you know its safe.

Pull the coil packs and check the dates on them. If they are close to original you should really think about replacing them. The coil packs go bad and can cause all kinds of issues.

I would also pull the intake and see if there is any damage or missing screws on the flaps.

Pulled injectors, link to pictures. Cyl 3 is pretty gunked, cyl 8 is dirty. Will get them tested/serviced this week. In the meantime, do I continue by pulling IM and if I do that, I might as well do the oil check valve service, right?

Through all the moving of ignition coils (between cylinders) to test different coils (2 of which are new) cylinder 3 has had both new and original coils in and no difference, and currently has an original (5/15/2014) coil on. Just pulled ignition coils: Cylinders 1-3, 5 and 8 are 5/14/2014 stamped, cylinder 4 is stamped 7/12/2012, cylinders 6 and 7 are new and have the same part # labeling, ELDOR, etc but the bottom line reads different: cylinder 6 - 2 09 F6 11 4 47/13 0 and cylinder 7 - 2 02 F6 11 4 46/16 0 - I’m not sure how to read this bottom line for a date.

(click here for pics - see notes in picture caption)

I pulled the injectors just a bit ago (PITA, stuck on super tight, even after some Pb Blaster…) and cly 3 injector is pretty gunked up and cyl 8 (original misfire back in june) is also a bit dirty. The rest look good. I’m going to take them all in for service tomorrow, get them back later this week or next.

One of the pintle caps (cyl 1) for sure fell down into the valves as I can see it and I think the same happened on cyl 5, though I haven’t been able to spot it down there, yet.
O-rings all came out, cyl 1 stayed in IM, cyl 2 and 3 had pintle caps loose but out of the IM and o-rings still attached, cyl 4 had everything still attached and actually fell out of the fuel rail as if it were loose. cyl 5 has pintle cap missing and cyl 6-8 all came out fully assembled like cyl 4.

Based on this I think I’ll have good results with cleaning the injectors. I’m thinking the ignition coils are new enough, maybe replace cylinder 4 stamped 7/12/2012 with a new one. Should I stop here, put it all back together and re-test or should I proceed with pulling the IM, which if I do that I figure I might as well do the oil check valve service. Thoughts?

The injectors are not usually prone to clog but you did the right thing there.

The intank pump tends to go bad and that could be part of the issue as well. Your fuel filter holds the FPR so you want to make sure that is good and working well. IF you saw some gunk with the injectors it might be a good idea to look at those two as well.

Don’t worry about the oil check valve its not going to be the savor of anything. If you pull the intake and you might as well if the prindle caps fell and just to make sure there are no other issues then you can just check the valve but there isn’t really a need to replace it. Even if you find it stuck. Clean the check valve and put it back in as long as its working after you cleaned it.

Just got a call back from the injector shop - said they were all a little dirty 11% restricted flow or something along those lines - picking them up later today. Said injector 3 and 8 looked no worse than the rest so I’m a little stumped again, was hoping to hear back that injector 3 was in poor shape.

I replaced the fuel filter 300 miles ago when cylinder 8 first had the misfire and I replaced the spark plugs and swapped cyl 8 and cyl 3 ignition coils. You mentioned intake pump - what exactly is that, any of these?
Intake Manifold front


1 Vacuum unit for intake manifold changeover
2 Knock Sensor (KS) 1 G61
3 Knock Sensor (KS) 2 G66
4 Intake Manifold Change-Over Valve V156
5 Secondary Air Injection (AIR) Solenoid Valve N112
6 Knock sensor 3 G198
7 Knock sensor 4 G199

Can you give feedback on my smoke test for the vacuum lines? Not sure if I was choosing appropriate locations or using false leaders with the hoses I chose.

in tank fuel pump.

Where did you tap in for the smoke test. If you pull all the plugs do they look the same color. Any sign of combustion instability

Ah, misread there. Will look into inspecting that.

Heres a link to the album with the most recent spark plug change when the misfire on cylinder 8 happened and I swapped cyl 3 and cyl 8 ignition coils. During the diagnosis once cyl 3 started misfiring and the misfire spread I swapped in two good spark plugs into cylinders 3 and 4 (from cyl 3 and 4 that I just swapped out 300mi earlier).

Here is a link to their current condition after being abused with misfire starting and testing.
(300 mi. Spark plugs 3 and 4 are from the previous set originally swapped out on June 07)

June 07 Spark Plug Change https://photos.app.goo.gl/EWuE6s7cRbyVuSdA2

Also, when I pull the IM (yes, still going that slow) am I going to be able to inspect/service the flaps easily enough or what are the steps there? Did a little searching and wasn’t coming up with what I thought I might need.

Also, I plugged into the vacuum T at the base of the oil filter housing, behind cyl 8 and tried pumping air into the T which just built up pressure in the smoke machine. Pumping smoke down the hard vacuum line heading down bank 2 toward the front had smoke release at valve N112. I also pumped smoke down the larger vacuum that feeds off thet throttle body inlet hose (hose between MAF and TB, has a vacuum line coming off it) and that just smoked out the TB, of course.

Just finished putting it all back together, battery topped off, codes cleared, TB reset… Took a minute to start up, cycled the ignition. Started up more or less fine for being off for several months and torn apart down to oil check valves and IM being split and resealed. Ran rough but was settling down then it slowly started getting more rough again, acting like before. I shut it off before it ran itself dead and pulled codes. Misfires on 1 and 3.

Misfire counts (1min 50sec run time)
Cyl 1 - 21,926
Cyl 2 - 0
Cyl 3 - 67,870
Cyl 4 - 0
Cyl 5 - 18,328
Cyl 6 - 0
Cyl 7 - 70
Cyl 8 - 210

Where to start diagnosing now?

Just did an initial smoke test and shows no leak, smoke is only escaping the micro leaks in my seal around the TB. I have not checked the in tank fuel pump but the injectors were pretty clean during their analysis and testing and the fuel rail was full so I was sorta ruling that one out.

I guess other thought is to take my mini torch, crank it open and not light it of course and move it around with the car running, truly test the no leak hypothesis

Its odd because the misfires increase gradually in count the longer the motor is running. ECU?

Its possible its the ecu as the ecu controls the amperage to the coil packs and 02s.

I assume if you unplug the maf the misfires keep going… That might be an easy thing to try. Also put a fuel pressure gauge on the rail to see where its at pre rail.

Was the cars timing system done or updated.

Lastly it might not be a bad idea to pull the crank trigger and clean that.

Any way to check the ECU for this? Brand new coil packs, injectors cleaned. I ran the Output Tests on the VAG and all the injectors fired off along with everything else that it ran.

Battery is sitting at 12.42 volts when not running anything

I can unplug the MAF while running next time I start it up. What is that going to indicate?

I will check fuel pressure, pre rail. Know what I should expect engine off and then while idling? Im also grabbing a few wiring bits to test the fuel pump.

Timing chain has not been serviced. Never any warm rattle and the only cold rattle was more of an exhaust rattle than chain slap so I am holding out hope it is not this. I figure I would be getting a lot more codes or more indication of timing being off yet it is usually just Cylinder 3 and then one or two other cylinders misfiring. It is killing me!

Crank sensor, I can replace easily enough. You mention cleaning it, just wipe down with brake cleaner or ?


Quick update/questions

Have tested the fuel pump relay and it checks out, resistance and all. I only hear the fuel pump when I turn the key to the On/ACC position, never when I open the door.

Tested the resistance in the fuel pump wiring and it checks out.

Next steps for fuel pump testing are to check the voltage getting to the fuel pump and make sure it matches the battery voltage. Then will test output of pump by opening power to the pump for 15sec.

With my resting voltage being 12.42 and the recommended ElsaWin voltage being 12.5, should I really get a new battery or just expect a slightly less output from the fuel pump (volume). Is my battery voltage a real issue here?

I’m fearing the fuel pump will check out as fine so then I’m thinking I need to check the fuel rail pressure, the crank position (g28) sensor and coolant temp sensor. Am I on the right path for what the misfires are showing or what else should I log on these cold tests?

Usually just checking the pressure at the rail is going to be good enough. Its good that your going beyond but even with checking out all of the pump voltage the ultimate needed end result is the pressure at the rail. The pressure regulator is in the fuel filter that can cause issues. We have seen new filters not function properly.

Unplugging the maf will allow the car to not read off all the sensors and just go into a fixed state this should ignore any possible interference that might be causing misfires if its not a hard mechanical issue.

Perfect all makes sense, thanks - will reprioritize!

Update -
tl;dr Had to prime the fuel pump and lines manually (ie couldnt prime by opening/closing drivers door or cycling to ON position) but the fuel pressure is steady if nothing else. Seems MAF could be bad, wiring or unit. Looks extremely clean upon visual inspection. Codes come up with cyl 3 misfire and MAF and Intake Air Temp Sensor (which is new, but related to unplugging the MAF?)

Battery - steady 12.66v resting; steady ~13.65v at initial idle; ~14.05v to 14.20v when misfire and rough idle begins
Fuel pressure -
55psi after priming and drops slightly to steady ~50psi resting and primed; steady 60psi when idling, even with rough idle and misfire. What is spec?
after priming fuel pump with a spare 12v and a jumper wire because the fuel pump wouldnt prime when cycling the key to the ON position. I double checked the fuel pump relay and fuse and they both check out. I also checked jumping car battery positive to the right side of the fuel pump fuse and checked voltage at fuel pump electrical connector and it is reading just about the battery voltage so the wiring appears to be good. However when I test the voltage at same connector when cycling the key to the ON position I get a reading of 0.10v which drops to 0.06v
Unplugged after the misfire and rough idle began. No change in behavior, RPM or anything so this indicates I guess bad MAF. I will look into cleaning and further diagnosis when I get back to AllData at the local library. Visually it looks great though the wire loom protection has worn through leaving still-in-perfect-shape wires ’somewhat’ exposed. Anyone know the textbook diagnosis of MAF for this engine?
Codes -
P0300 - 001 - Random/Multiple Misfire Detected
P0303 - 001 - Cylinder 3 - Misfire Detected (counts seemed better but screwed up the logging)
P0102 - 002 - Mass Air Flow Sensor (G70) - Signal too Low - Intermittent
P0113 - 002 - Intake Air Temp. Sensor (G42) - Signal too High - Intermittent

Next steps?