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Good morning all

Next, the EML has been on for some time. One of the EGT's originally.

A few months ago i started getting something that felt like a misfire when accelerating quickly to overtake etc. The engine would 'Cough' and then go. Plugged it in but no fault codes.

I had the main dealer put 2 new Mafs on whilst it was in for a service as they were 4 years old according to the service record of them last being changed. Problem solved

Next issue. I was driving along and braking to a stop when the engine started to idle really lumpy. I put the box into N and give it a a blast on the loud peddle.....all was fine. A few days later on startup it did the same thing. It started and then it ran lumpy as hell. Turned it off, turned it on a few hours later and all was fine

Plugged it into a diagnostics and got the following codes:




Now im hoping that some of you Guru's will say 'its this and this and this, needs changing, job done'

I am going to take an educated guess at the issue just being the Bank 1 pre cat lambda (which side is this?) and the Exhaust gas temp sensor 2 (which side is this?)

Might it be that i have left the EGT repair too long and it has damaged the o2 sensor in some way?

Thanks in advance!

Sounds like you've got a good theory. Have you reversed into anything recently? Maybe could the exhaust and damaged the sensors?

Bank 1 is the left looking at the engine from the front of the car.

Shoppinit wrote: ↑

Thu Apr 26, 2018 10:49 am

Sounds like you've got a good theory. Have you reversed into anything recently? Maybe could the exhaust and damaged the sensors?

Bank 1 is the left looking at the engine from the front of the car.

Nope i havent reversed into anything ever but the EGT sensor has brought up a fault for the past 6 months/8000 miles.

Both banks have fueling issues though it seems, i wonder why this is

Anymore pointers in the right direction would be great

I will also speak to Unit 20 when i get there next week as it is booked in for a gearbox oil change with them

Air leak is the most obvious thing to check. Maybe SAI combination valves. Check those and the vac hoses.

Shoppinit wrote: ↑

Thu Apr 26, 2018 12:45 pm

Air leak is the most obvious thing to check. Maybe SAI combination valves. Check those and the vac hoses.

Do you think a smoke test would show any air leaks? Maybe this is something Unit 20 will be able to do?

You're in good hands with Unit 20. Don't know about a smoke test. Suspect the leak would have to be large.

It doesnt do it all of the time though

It has a little moment, then it runs perfect. I have never been to Unit 20 as i have not owned the car long so next week will be my first visit

The fact that you've got both too rich and too poor DTCs is troublesome. Also, they are all intermittent except for the too weak on bank 1. After changing the MAFs did you reset the old fault codes?

Bad EGT will give a bad mixture, so will O2 sensor. Maybe it's a coincidence that they've both gone. They are on different banks, after all.

Might be worth logging the throttle position. I really wish the RS6 had a fuel pressure sensor. When my fuel pump went on the Volvo it was so easy to diagnose by logging the fuel pressure.

Might be worth checking the wiring to the MAFs, when mine had a broken wire it threw rich and lean codes for both banks, the wires are easily damaged removing the air box. TPS sell the plugs and wires as a repair kit, fixed mine last year.

As a conclusion to this FIXED

Took the C5 to Unit 20, they serviced the gearbox as normal and one of the technicians spent 1 hour on the car doing diagnostics for the fault above.

Turns out it was the airbox seals that were not seated properly, or the airbox not seated properly. They fixed the problem by doing it properly (unlike the main Audi dealership that changed the MAFS)

Drives absolutely great now and my MPG has risen up to nearly 18mpg over the last 1000 miles of normal use!

The engine light was reset and has not come back on since

Hope that helps someone

Good outcome.

Common mistake by some refitting the airbox apparently; you would have thought Audi techs might get it right though