Audi Q7 (2012) Misfire with cylinder 4,5,6 only, please help to diagnose

RTFB yet???????

Page 24 of that SSP suggests this engine has A MAP & 2 Charge Air Pressure Sensors. All with integral Intake Air Temp ??? But no MAF ???

Or have I read that wrong ?

Dr Sheldon said:

Page 24 of that SSP suggests this engine has A MAP & 2 Charge Air Pressure Sensors. All with integral Intake Air Temp ??? But no MAF ???

Or have I read that wrong ?

Click to expand...

It is correct that no MAF, instead they have two Charge Air Pressure Sensors at two sides of the banks.

Anyway, after visiting the Audi service with their conclusion on timing chain and fuel injectors, I bought the car to a workshop with the technician who used to work for VW. He concluded that there is no problem with timing chain as well as fuel injector after he got a drive test, check EVAP with smoke, and scanned the car. He also thought that random misfire on only the bank 2 is very strange and could not think of a reason. In short, it is very different between conclusions of the Audi service and the technician.

Anyway, I used the measure blocks to monitor the Knock sensors. It was surprised that the Knock sensor of the cylinder 4 is much different from the others (up to 1.8V while the others are normally at 0.6-0.8V). The knock sensors of the cylinder 5 and 6 also varied in the range of 0.5-1.0 but never went up to 1.8V as the cylinder 4.

Do you think whether the Knock sensor of the bank 2 is defective. If so, it could be hard to open up and swap the Knock sensors of the bank 1 and 2 to check it.

What you could do is at the ECU, you could open/extract pins using RTFB/WD for any sensor and disconnect and use a balance cheat wire from other alleged knock sensor you believe is good from opposed bank, huh?
Just costs time and no need to confirm by disassembling the engine.
Cool thing about banks huh?

NostraJackASS Has Questioned?

For what it is worth, almost all missfires are in 4 and 5, seldom in 6, occasionally.

Bank 2 is chopping a lot of fuel, -22/23. I would maybe swap injectors from bank 1 if easy.

Don't know the dynamics of VAG on this engine, what is the fueling times on these injectors, or maybe does not apply here.

I used to try to swap the Knock sensors of the bank 1 and 2 as you said but it was not easy due to compact wiring of this version.

Anyway, the summer is coming here with the temperature above 10C, thus the engine light has not been on for more than a month (2000km). In order to confirm why, I had a drive test and online measurement yesterday. There was still random misfires on cyl 4,5,6 but the max count was only up to 6 times, and then reseted - that 's why the engine light was not on. The knock sensor on cylinder 4 was up to 1.8V - very different from the the other cyls 0.6-0.7.


It is really hard to predict what is the main problem/reason afterwards!!!

Larry Manton said:

For what it is worth, almost all missfires are in 4 and 5, seldom in 6, occasionally.

Bank 2 is chopping a lot of fuel, -22/23. I would maybe swap injectors from bank 1 if easy.

Don't know the dynamics of VAG on this engine, what is the fueling times on these injectors, or maybe does not apply here.

Click to expand...

It is not easy at all because you have to take the rooster turbo off to see the injectors and knock sensors!