poor fuel economy Help to diagnose Audi A4 B8 please

[george_nn]

Hi,
I have an Audi A4, B8, Multitronic, 2.0 TDI and it has developed some symptoms:

- increased fuel consumption (poor mpg)

- slight engine shaking but become worse when I switch off the engine (the whole car shakes a lot more on the moment between pressing the key to switch off until the engine dies completely)

- a while back I've noticed that for the first time on the day the car won't start at first attempt but at the second. Now, it will not start after 3-5 attempts. I press the key, the engine cranks but just when it's about to fire, it dies like something it's not there, like the fuel just ran out. When it won't start, the cranking time is the same as when it does start, the car does not crank longer. It will happen only when I use the car for the first time on that day after which the car will start at first attempt perfectly fine every time until next day. Battery is new/good and it's summer at the moment.

There are no fault codes on VCDS. However, after my research, I think there is an issue with either MAF sensor or EGR (or both).

I have attached 2 screenshots from VCDS with engine at idle, do these values look abnormal?

Thank you,
George

[Steve Q]

Any fault codes? 

Could it be a cam sensor? 

Maf sensor? 

[george_nn]

I've scanned it multiple times with VCDS and there are no fault codes. Also, I've been to various garages, they've also scanned it and found nothing.

I did think of cam sensor but I cannot locate it. Engine J623-CAGA. Any directions or pictures please?

This morning I have disconnected the MAF before starting the engine but it made no difference, still didn't start at first attempt. I would imagine is not the MAF in this case? Also, looking at the above VCDS pictures, Air mass: specified value and Actual air mass are similar so I assume that's good, right?

Cheers!

Edited August 19, 2023 by george_nn

[Steve Q]

In the old days if maf was at fault more often than not the engine would run better so I'd cancel.tgst out. 

Not sure where the can sensor is located. 

Could it also be a lambda sensor? 

I'd also advise Changing the spark plugs and ht leads. 

[george_nn]

When the MAF sensor is disconnected, the car runs about the same, I don't notice any difference.

The car has new glow plugs.