Random multiple misfires, and strange noises

[slineb7]

Good morning guys. Sorry for the essay, I just want to set the stage.

So I had a random CEL for multiple misfires, showing across both banks in random cylinders at different times (leading me to believe it wasn't coil related). Initially when it happened, I took her in to get checked out, and the dealer said it was the crankcase breather valve and hoses that were allowing extra air into the chamber, causing issues. They tested it with an aerosol propellant, and showed that it was the issue. So we got that replaced. $1k gone

Drove her for about 3 weeks or so, and under the first real load I gave her, got the flashing CEL and backed off. Showed random multiple misfires so I limped her home (not limp mode, just gentle) and parked her to wait to get the scan done. Once scanned, it showed again, random multiple misfires, but this time exclusively in cylinders 1 and 5. Now I was thinking the best way to eliminate coils from the equation was to get them done. So last night I replaced them all with the red tops, part 06E905115E, purchased through the dealer through a solid connection. I unplugged the battery to clear the codes, and when I started her back up, codes were gone, CEL was gone, and all seemed well for the 5 minutes that I left her idling.

Fast forward to an hour ago, I started her up to take her to work, and heard a very strange noise, coupled with a CEL. It was repetitive, and the best way to describe it is if you make the sound "boop" with your mouth with some bass in your voice. The sound happens quickly, and repeats cyclically, almost like it is happening in connection with the spark. So I immediately killed the engine and panicked for 3-4 seconds before I cleared my head. I restarted her with my phone in video mode to capture the noise, and the sound was gone, but the CEL came on solid, after 5 seconds flashed, and after 5 more seconds stayed solid. The idle was also causing vibration in the car, slightly more than usual (my motor mounts are bad). I gave her about 1200 rpm and the vibration left, noise did NOT return, lights stayed on, but all sounded normal.

To be safe, I left her parked and took the beater to work.

My questions are:

• What the hell was that sound? I've never heard it before, and almost didn't think it was coming from the engine because it isn't one I've heard before. I really hope it isn't detonation..
• What else should I pursue to address the misfires? I was going to wait to do plugs until I got the CC done, planned for January
• It has been 25k since the last CC. Is it time?

I appreciate the support. Any constructive feedback, questions, and comments are welcomed.

-Jamil

[OscarMeyer]

Are those coils packs actually for an RS4, never seen red tops?

What's the miles on the car? I have the same issues but have narrowed it down to a bad pcv(which you have done) needing a carbon clean and new or rebuilt injectors. Which I have sitting in my garage waiting to be installed.

I'd say if possible log your fuel trims and see if your getting requested values for your fuel pumps.(pressure at the rail) If you are I would think it could be injectors, but I am not 100% on this. I'm at work and have a no phone policy will check it at my lunch break.

[slineb7]

Miles are 128k, last CC done at 105k.

The red tops are supposedly for the R8, and Stefan at 034 mentioned that those would work just fine for my car. In reality, they ended up at the same price as the stock black Rev F ones, and if they were compatible, I thought that the aesthetics worked better than the blacks for my engine bay. Can anyone else chime in if this was a bad move?

I'll have to get a cable first to log the fuel trims, but I think it's time to do it anyways. I appreciate the prompt response.

[jakeoboy67]

did you scan it for codes before you parked it ?

there might be something else than misfires showing up.

[slineb7]

@jakeoboy the last scan was done prior to coils, and showed misfires on 1 and 5. After the coils, I haven't scanned yet but I will shortly and will report back. I'm not sure if what I'm hearing is knock, or if it is an air leak.

[lucidmatt]

Not much to offer except Ive been running R8 coils for the past 10 months/9000 miles without one hiccup. In my experience, these are more than suitable especially with the RS4 engine management and the fact that the motors are for all intents and purposes the same as the ones in the R8s. The coils themselves are way more robust than any other coil packs I have used.

Please excuse my tangent: I converted the OEM coil packs on my 1993 S4 to 1.8t coil packs back in 2010, the amount of spark dwell and underhood heat of that motor popped coil packs every 2000 miles. Went to the newest gen 2.0t in 2011, and it went to 5000 miles before a coil popped. in 2013 I tried R8 red tops and 20,000 miles later not one had popped.

[OscarMeyer]

did you scan it for codes before you parked it ?

there might be something else than misfires showing up.

Totally forgot to ask that, but doing a scan would be a big help for other codes, if any are there.

And good to know about the R8 packs, can rule one thing out

[your daddy]

copy the scan. get rpms, temp, etc.

[slineb7]

So I ran the codes with a scanner again. Misfires on cylinders 1,3,5,7. I cleared them and started the motor. It started up fine with a rougher than normal idle, then I heard the noises again twice, immediately followed by the scanner reading misfires on 1 and 3.

Am I completely inept here, or do the coils not sit absolutely flush with the valve covers? Mine are slightly off flush by about 4mm from bottom of coil to top of VC. They were pushed in as far as they can go.

Does it make sense to swap plugs too at this point? I can't figure out the noise, it sounds like a burble, but my first description still holds. Anyone have any ideas before I have to take her in to see a surgeon?


Sent from my iPhone using Tapatalk

[slineb7]

So I feel like an idiot. I unplugged and re plugged all coils, thinking I missed something in the connections. It honestly sounded like a couple cylinders weren't properly engaging ignition.

Then the problem went away. Maybe I am inept... Lol.

I appreciate the feedback from all those who took the time to reply. Basically I had to reconfirm the harness connections to the coils. Took her for a ride and she pulls harder than before. Idle worked itself out too.




Sent from my iPhone using Tapatalk

[ven0m]

It's good the problem worked itself out in the end.
Don't feel bad about it. Take it as a learning curve for next time to plug/unplug coils if you have any issues after changing sparks/coils. Could have happened to anybody, we are only human. :)

[slineb7]

So now the misfires are sporadic... Last code bout was cylinders 1, 2, and 4. I wiggled the coils and ensured engagement on the harness and they are now gone. Is this a harness and clip issue? Is there an incorrect way to insert the coils?


Sent from my iPhone using Tapatalk

[ven0m]

You can't plug them incorrectly, but it's a connector and connectors are worn out over time and the pins also oxidate/wear over time. Our cars are old.

[slineb7]

What is the difficulty level to replace the ignition coil harness? Are there prints for it? Need to dig up the old Bentley manual..


Sent from my code scanner using Tapatalk

[slineb7]

Bumping for new discoveries. I've noticed that the misfire issues only happen under two circumstances: 1- if the car has been sitting overnight or similar, and 2- only at startup until after the SAI kicks off. After it kicks off the misfires disappear And it runs like normal.

A scan shows that the misfires are routinely on cylinders 1 and 5 exclusively now. Does it sound like the injectors need work, or possibly the plugs? Is the SAI possibly a root cause? Kind of an odd thing here.


Sent from my iPhone using Tapatalk

[S42RS4]

Bumping for new discoveries. I've noticed that the misfire issues only happen under two circumstances: 1- if the car has been sitting overnight or similar, and 2- only at startup until after the SAI kicks off. After it kicks off the misfires disappear And it runs like normal.

A scan shows that the misfires are routinely on cylinders 1 and 5 exclusively now. Does it sound like the injectors need work, or possibly the plugs? Is the SAI possibly a root cause? Kind of an odd thing here.


Sent from my iPhone using Tapatalk

Sounds like injectors are going bad esp the miles you have on your car. I was having the same problem and I went ahead and replace my injectors and I don't have a misfire problem no more. What percentage is your STFT/LTFT?

[slineb7]

I have to get a VCDS cable to log that info. That's the next "mod" on the list.


Sent from my iPhone using Tapatalk

[ven0m]

The SAI will steal a bit of air from the airbox on startup as it feeds the air via the combi-valves directly to the exhaust manifold, to get the CAT's up to operating temperature ASAP.

Could be, you're experiencing the misfires due to running a bit wet on cylinders 1 and 5 when the manifold is air deprevated on startup - possible leaking injectors. (take this as a guess, I'm assuming that the air deprivation to the complete manifold during the SAI phase exposes the fault of the bad injectors just enough that you get a few misfires in that time)

[slineb7]

I appreciate all the responses. I'm planning an injector rebuild, and a CC while I'm in there. Should help ease my mind about carbon since it has been 28k since the last one.


Sent from my iPhone using Tapatalk