Misfire Issues_please help!!

[Batman0424]

I have posted in a couple threads, but wanted to create a consolidated thread and ask for some advise.

Details on the car and mods:
2015 S4 with ~16k miles
EPL Dual Pulley + DSG
ECS Intake
AWE Touring + Stock Downpipes

Starting earlier this year, I began experiencing intermittent sputtering issues while EPL Stage 1 with DSG. This would only occur when I rolled on the accelerator at higher RPMs (usually above 4k RPMs) and last a couple hundred RPMs. No codes were ever thrown.

Prior to going Dual Pulley, the plugs were changed and the dyno tuning went well (at EPL). At the same time this was installed, I also had the HPFP installed.

After going DP, I started to experience sputtering again, a bit worse and at lower RPMs. Still no codes. Had the plugs changed again and changed all coils, but the issue continued.

Then, a couple months ago, I threw a CEL and EPC with Cylinder 1 Misfiring. I thought, finally, we have a place to start. This turned out to be a bad fuel injector. Injector replaced and reverted back down to the Stg 1 file. All was ok for a bit, but then EPC came on again with Cylinder 2, 4 and random misfire codes. Cleared these and car drove ok. Keep in mind here, there was no more sputtering once I dropped down to Stg 1.

Two weeks ago, I threw another CEL and EPC with Cylinder 5. This turned out to be another fuel injector. This was replaced and I threw in some Techron (wanted to use BG44k, but this wasn't available locally - might order this next) when I picked the car up yesterday.

During my drive home, again throw a EPC with Cylinder 4 Misfire (no CEL). Also, when I was reviewing the codes, I noticed a P310B Low Pressure Fuel Regulation code. However, the Fuel Pressure code was triggered in the morning (close to when I added Techron, but it is likely this was 10-15 minutes before Techron was added) and the misfire was during the evening commute.

So, here we are now. I am not sure how best to proceed or what I should start swapping. I have considered that there might be an issue with the cats, maybe the Pressure Control Value, maybe the LPFP (although the fuel pressure code is new and I have been experiencing sputtering / misfire long before this code).

Is there anything I am missing here? Anything I should be looking at?

P.s., Tony and Chris at EPL have been helping me through this the entire time (since May). We have done a few remote sessions and I send them all of these issues. I feel bad drowning them with all of this and since they are not local, I am using a shop near me to work on the car, thus this post to help point the shop in another direction.

[bhvrdr]

Sounds like you are on the right track to hunt down the gremlin (check cats and in-tank pump). You may also want to make sure the fuel filter didnt get contaminated.

Mike

[Batman0424]

Sounds like you are on the right track to hunt down the gremlin (check cats and in-tank pump). You may also want to make sure the fuel filter didnt get contaminated.

Mike

Thanks Mike. Do you believe this could be anything simpler? I am tending to lean a bit toward the fuel system, specifically the filter / pump as I have had two injectors fail (maybe some bad fuel clogged the filter and small debris could be breaking lose and clogging the injectors - sputters and misfires only happen under hard acceleration now).

[bhvrdr]

Thanks Mike. Do you believe this could be anything simpler? I am tending to lean a bit toward the fuel system, specifically the filter / pump as I have had two injectors fail (maybe some bad fuel clogged the filter and small debris could be breaking lose and clogging the injectors - sputters and misfires only happen under hard acceleration now).

yeah i'm wondering the same thing you are. Im wondering if something is killing the injectors but Then I was also wondering if two perfectly good injectors got replaced and its really the cats. Start with the cheapest diagnostics and work up from there I guess. I agree that the fuel components seem more likely now with your new LPFP code.

[Batman0424]

yeah i'm wondering the same thing you are. Im wondering if something is killing the injectors but Then I was also wondering if two perfectly good injectors got replaced and its really the cats. Start with the cheapest diagnostics and work up from there I guess. I agree that the fuel components seem more likely now with your new LPFP code.

It is good to hear that our thought process here is the same. It is hard to look at this from two directions (injector failures being related or coincidental) and draw conclusions.

[SwankP3RF3ct10n]

Change the in-tank LPF pump assembly. If you're not getting enough fuel, you'll sputter like that. Some people early on were having quirky things when the B8.5 cars first started being tuned and it's as almost the fuel pumps put in the newer cars were detuned to deter tuning or something. Anything other than stock tune would cause issues on them for some reason. I'd flash back to stock tune and see where you are for a couple of days while you wait on the new pump assembly (pump/filter) to arrive, but that's what I'd replace next. Make sure you run the tank down until your gas light comes on so that when you change the pump, it's easier and you don't have to worry about overflowing gas from the tank, etc.

[Batman0424]

Change the in-tank LPF pump assembly. If you're not getting enough fuel, you'll sputter like that. Some people early on were having quirky things when the B8.5 cars first started being tuned and it's as almost the fuel pumps put in the newer cars were detuned to deter tuning or something. Anything other than stock tune would cause issues on them for some reason. I'd flash back to stock tune and see where you are for a couple of days while you wait on the new pump assembly (pump/filter) to arrive, but that's what I'd replace next. Make sure you run the tank down until your gas light comes on so that when you change the pump, it's easier and you don't have to worry about overflowing gas from the tank, etc.

Thank you for the input, this sounds like a good approach. How difficult is it to change this assembly?

[SwankP3RF3ct10n]

Thank you for the input, this sounds like a good approach. How difficult is it to change this assembly?

There's a writeup on there I think with someone doing it, but it's not hard at all. Well, I say that because I've changed in-tank pumps on other cars before, so I wouldn't have an issue doing it. It's basically, take the back seat cushion out, take a cover off, unplug some electrical plugs and lines and then undo the ring that holds the assembly lid in place and take it out. Swap parts and reverse the process to put it all back together again.

[Batman0424]

There's a writeup on there I think with someone doing it, but it's not hard at all. Well, I say that because I've changed in-tank pumps on other cars before, so I wouldn't have an issue doing it. It's basically, take the back seat cushion out, take a cover off, unplug some electrical plugs and lines and then undo the ring that holds the assembly lid in place and take it out. Swap parts and reverse the process to put it all back together again.

Doesn't sound too bad. Before kids, I would have gladly tackled this one, but my free time is super limited. I dropped my car back off at the shop (wife's car was there for brakes and and oil change) and will have this new pump and filter installed this week.

I am going to continue searching for what else could be causing this issue.

[Lthartigan88]

Pre cat 02's? Mine were having a misfire in 2 and 4 and only thee the code for the 02's sometimes so it always had me confused


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[Batman0424]

Pre cat 02's? Mine were having a misfire in 2 and 4 and only thee the code for the 02's sometimes so it always had me confused


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I haven't consider those yet.

Did you always throw a code for the O2 sensors?


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[Loe]

before changing your LPFP, can you log your actual/spec fuel rail pressures?

[Loe]

Log these:
Engine speed
Accelerator position
Short term adaptation of mixture formation bank 1
Short term adaptation of mixture formation bank 2
Actual fuel rail pressure
Fuel rail pressure: specified
Fuel pressure
Long term Fuel Trim bank 1 (I forget the name of them)
Long term Fuel Trim bank 2 (ditto, but should be similar to short term)

[Batman0424]

before changing your LPFP, can you log your actual/spec fuel rail pressures?

I will try to get to the shop today to log before they work on the LPFP. I decided to leave my car there yesterday because I was picking up my wife's car and this shop is an hour from home (near work, nothing local to my house that I trust).


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[madman4you]

See if the shop can toss a gauge for checking back pressure on the cats. If the gauge shows a ton of back pressure, you may need to replace a cat(s)

[Batman0424]

See if the shop can toss a gauge for checking back pressure on the cats. If the gauge shows a ton of back pressure, you may need to replace a cat(s)

That's a great idea. I've been wondering how to best check this and have been looking into using a boroscope, but back pressure sounds like a better option. I'll ask them today.


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[-leman-]

Log these:
Engine speed
Accelerator position
Short term adaptation of mixture formation bank 1
Short term adaptation of mixture formation bank 2
Actual fuel rail pressure
Fuel rail pressure: specified
Fuel pressure
Long term Fuel Trim bank 1 (I forget the name of them)
Long term Fuel Trim bank 2 (ditto, but should be similar to short term)

+1 you should definitely log before replacing any non-consumable parts.

It would not hurt to replace the in-tank fine fuel filter and take out the whole LPFP assembly to inspect the coarse mesh filter. Not that I think it is your issue here in any way but I once had an issue with my fine fuel filter when it got clogged to the point that fuel pressure in my low pressure fuel loop was almost zero. The car stalled and I was unable to start the engine anymore. I'm still puzzled how this happened in the first place (as it happened basically on the move, so a type of situation when the car ran just fine a couple of minutes ago and then all of a sudden I get no fuel at all) but the issue was gone after just the fuel filter replacement.

[FWP!]

Log these:
Engine speed
Accelerator position
Short term adaptation of mixture formation bank 1
Short term adaptation of mixture formation bank 2
Actual fuel rail pressure
Fuel rail pressure: specified
Fuel pressure
Long term Fuel Trim bank 1 (I forget the name of them)
Long term Fuel Trim bank 2 (ditto, but should be similar to short term)

+2

[A U D I]

Consider maybe it's a gas problem. If the fuel you are using is from a bad gas station you would not see it while stock or even as much stage 1 tune. This could be why 2 fuel injectors went bad also. My suggestion on it would be to swap the fuel filter because of the problems but after change the gas station you have been using. At 16K miles I wouldn't think injectors are failing for production issues.
What gas are you using ?

[Batman0424]

I'll do some logging over the weekend.

I typically use Citgo, but also Shell and Sunoco when I pass those stations. A couple times I filled up at a Speedway (I regret this) as I was very low and no other station was close.

I'll have the shop swap the filter for now and then see how that goes and how the logs look. Hope to have my car back tomorrow.


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[Lthartigan88]

Yes sorry for the late response man, always threw a code for my post cats because my tune but they don't affect anything. I started noticing misfires and slow ass limo mode and it turned out to be my pre cats 02's. Those two codes made my car run like shit and misfire but the code would be thrown very randomly it was almost hard to catch


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