B8.5 Misfire Issues

[ferndj02]

I'm having issues with my 2014 A4. I was due to change the PCV for some time due to O2 Sensor Codes (O2 Sensor Bank 1 Sensor 2 Delayed Response Lean to Rich, O2 Sensor Bank 1 Sensor 2 Delayed Response Rich to Lean, Catalyst System, Bank 1 Efficiency Below Threshold). The car seemed to run ok up until last Wednesday.

The temperature outside warmed up (30 to 70 in 3 days) and when I got home on Wednesday, the car started misfiring at idle when I pulled into my driveway.

I let the car sit for a few days thinking maybe it was just the PCV issue, and I really needed to get off my ass and change it. I replaced the PCV, and the car is definitely running better. I'm not getting anymore O2 Sensor Codes, but I still have a misfire on Cylinder 1 and a Random Misfire CEL.

I replaced the spark plugs this morning and swapped the coil packs around.

Now I'm getting an additional P125000 (Fuel Level too Low) code. I have a full tank of gas.

I had a carbon cleaning about 10,000 miles ago along with new fuel injectors.

I haven't run a compression test yet on cylinder 1, but I'm working on that.

Any ideas?

[adamleaf8601]

Could be the high pressure fuel pump. How many miles on the car?

[audrobotic]

I assume that after you swapped plugs and coils around you still got the same cylinder #1 misfire. (plus the new fuel level low code).

The compression test is a good idea. Sounds like its a fuel delivery issue. But youll have to take a fine tooth comb to everything air to track down the culprit. Maybe one of new injectors is bad or clogged.

[ferndj02]

Could be the high pressure fuel pump. How many miles on the car?

70,000 miles.

[ferndj02]

I assume that after you swapped plugs and coils around you still got the same cylinder #1 misfire. (plus the new fuel level low code).

The compression test is a good idea. Sounds like its a fuel delivery issue. But youll have to take a fine tooth comb to everything air to track down the culprit. Maybe one of new injectors is bad or clogged.

Yes - it's still cylinder 1 after plugs / swapping coil packs.

[ferndj02]

Just tested the compression. Cylinder 1 is about 10% lower than the rest.

[DannyFB8]

Sad to say, this sounds a little all to familiar. Your next test should be a leakdown test. Had similar symptoms on my b8.5 throwing excessive misfire codes even after changing, injectors, pvc, new plugs. Did the leakdown test and cyl 1 kept failing and came to find out I had a scorn cylinder 1.


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[ferndj02]

Sad to say, this sounds a little all to familiar. Your next test should be a leakdown test. Had similar symptoms on my b8.5 throwing excessive misfire codes even after changing, injectors, pvc, new plugs. Did the leakdown test and cyl 1 kept failing and came to find out I had a scorn cylinder 1.


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I drove it today while watching the misfire counter. It only seems to do it at idle. It doesn't do it when I step on the gas. Did you have those symptoms?

[DannyFB8]

I had misfires at both idle and while pressing on the gas. Car was reluctant to start but after a couple of crank it did but I had also multiples other symptoms that supported the scorn cylinder such as oil leakage between timing chain cover and head block, 0 compression from cyl 1, oil deposits. Are you getting any of those?


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[ferndj02]

I had misfires at both idle and while pressing on the gas. Car was reluctant to start but after a couple of crank it did but I had also multiples other symptoms that supported the scorn cylinder such as oil leakage between timing chain cover and head block, 0 compression from cyl 1, oil deposits. Are you getting any of those?


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Not yet, thankfully. Compression seems ok on Cylinder 1 and no oil leaking or excess burning. Seems like it's either fuel related or a vacuum leak.

[ferndj02]

Update - Replaced the breather tube, removed the O2 spacers I was using before I was tuned, and tightened down the PCV a bit more.

The seems to be idling normally now and the ticking sound is gone. Cylinder 1 seems to misfire still when I let off the gas. Might be another vacuum leak somewhere...

[ferndj02]

Update to the update: it was a failed fuel injector. Ironically, I replaced the injectors 10,000 miles ago.

The car was much better after that last update but got progressively worse. I replaced the O2 sensors because I had been getting a delayed response error. It didn't fix the cylinder 1 misfire. So I replaced the fuel injector feeding cylinder 1.

Hope this helps the B8.5 guys.

[rockstar143]

Update to the update: it was a failed fuel injector. Ironically, I replaced the injectors 10,000 miles ago.

The car was much better after that last update but got progressively worse. I replaced the O2 sensors because I had been getting a delayed response error. It didn't fix the cylinder 1 misfire. So I replaced the fuel injector feeding cylinder 1.

Hope this helps the B8.5 guys.

This not only helps but confirms issues I've been following as well.
I did a valve cleaning and after that have been chasing down a misfire as well.
Finally I tracked it down to one injector, new one is on the way.
SO annoying but once it's all figured out I will feel like an expert.