B7 S4 Misfiring Please Help!

[B7_S4]

Hello all,

Thank you in advance for the help and advice.

I have a B7 S4 and when I was driving down the highway my CEL came one. Pulled over to see if there was anything visibly wrong under the hood, and to my inexperienced eye, I didn't notice anything or any noise that seemed odd. Topped it up with some oil just to be sure it wasn't low. Once I got back into the city, I briefly smelt the rotten eggs smell (I have heard this can result from a bad/clogged cat). I also had a massive loss in power above around 3,800rpm. Exhaust node seems to be inconsistent(muffled) out of the left muffler and seems to have less fumes being emitted and the right side seems normal and consistent (symptoms of bad cat once again?)

Car isn't making any strange noices and seems completely normal at idle with no shaking or rattling but as previously stated a huge loss in power.

Took it into my local and trusted Audi/VW shop and they did 2 hours of diagnosing with no answer. Said they swapped around the plugs and coils and although the plugs looked like garbage (and recommeded replacing) said both of those weren't the issue.

Hooked the car up and showed the following codes:

Warm Up Catalyst; Bank 1
P0421 - Efficiency Below Threshold - Intermittent

Fuel Trim; Bank 2 (Multi)
P1130 - System too Lean- Intermittent

Cylinder 1
Random/Multiple Cylinder Misfire Detected
P0300 - Mil On

P0301 - Misfire Detected - Intermittent

Cylinder 2
P0302 - Misfire Detected - Mil On

As step 1, I am replacing the spark plugs tonight. Will do the coils if no change.

If you have any suggestions, I appreciate any help I can get. Thank you!!

[B7_S4]

I changed the plugs and coils and there is no change.

When I step on it, it seems as though the car has a muffled/fluttered sound and power is being held back or restricted.

[icanfly]

If you've done plugs and coils and still have the issue, it's possible that it's a timing / chains issue. The sound is interesting, it sounds mechanical in nature. Can you get a little more footage, perhaps under power - driving?

[Denali70]

Did you ever figure out what the issue was? I recently has a coil pack fail, I replaced the one pack and all 8 spark plugs. The CEL went away and the car accelerates, but it feels bogged down and doesn't have the power it normally does. Every now and then it will feel back to normal. Is it possible that the other 7 packs are just weak or would it misfire?

[Jesse Sheridan]

Did you ever find out what was going on? I'm having the same problem..

Sent from my Alcatel_5056O using Audizine mobile app

[t1gertea]

Possibly a clogged precat

[badger.]

is your intake flapper still functioning correctly?

[AudiquattroRS4]

I have power loss on mine as well with EPC and CEL lights on. EPC is intermittent. My code is P020 and P015. Yours sounds like Cat. Leak. Just saw a video of how you can test if your cats are clogged with pressure sensor. Good luck


Sent from my iPhone using Audizine

[B7_S4]

Had some time to look at the car again today and it seems to be making a fluttering type noise while revving the motor in neutral. Not sure if it's a timing chain related issue (tensioner/adjuster) noise or something else but sounds the same way the car acts when hitting 3,800 rpm.

Here is a video revving the motor while parked.
https://www.youtube.com/watch?v=61v4QnNCXk4

[B7_S4]

Any ideas on what that spuddering sound could be?

[B7_S4]

Update*

After replacing the spark plugs and coils, there was no change in symptoms. I brought it to a nearby shop and they recommended changing the Crankcase Ventilation Valve. I replaced the valve myself and there seemed to be improvement as the car doesn't seem to shutter but there is still a huge lack of power.

I also unplugged the MAF to see if that was a possible issue. The car idled the same but had no power when driving unplugged. That means the MAF is still good right?

Does anyone have any other suggestions on why this could be? I am tired of taking taking it to the shop and spending money with no results...