Increased fuel consumption after fixing EGR cooler ways.

[imperia]

Hello,

My Golf MkV BMM was making hissing noises. It was leaking exhaust gasses from well know spot:

The mechanic isolated the whole EGR cooler by putting a metal cap around point 15 and 16:

With this manipulation I was getting error P0401 Insufficient flow. (naturally)

After some time, the air found his way out again and started hissing again by leaking somewhere around gasket 15.

I decided it is time to fix my EGR cooler and bought new gaskets (15, 8 and 12)
I also fixed the EGR cooler by doing this:

Everything is fixed now and I am not getting error P0401 anymore, also hissing is gone, but my fuel consumption has notably increased.
I was expecting better fuel economy after fixing the leaks, but alas.

I looking for help, what may be the cause for this bad fuel economy?

Thanks for your time.

 

[oilhammer]

Subjective. Define "bad". You had leaks before, and any leaks in the EGR tract (meaning, after engine but before turbo) will equate to a loss of charge air on the intake side. Exhaust pressure is roughly 150% of intake pressure (otherwise an EGR wouldn't work on a forced-induction diesel). You had a loss of boost before, which means loss of fueling, and less power, since the ECU is calculating fueling based on load and boost. So your fuel economy with a poorly running engine may indeed have been better. Now that it has all its [potential] power, it can and will use a bit more fuel in theory, depending on how you drive.

You have also (it looks like) disabled the EGR cooler's ability to do its job. So THAT may also be causing a higher than ideal EGR temp going into the engine, which will also reduce power and reduce economy.

 

[imperia]

So your fuel economy with a poorly running engine may indeed have been better. Now that it has all its [potential] power, it can and will use a bit more fuel in theory, depending on how you drive.

Ok. I understand.

You have also (it looks like) disabled the EGR cooler's ability to do its job. So THAT may also be causing a higher than ideal EGR temp going into the engine, which will also reduce power and reduce economy.

I actually fixed the EGR cooler to work now. It was disabled (isolated) since when I bought the car one and half year ago. I had great economy back then with EGR disabled.

Maybe something else is the reason, but now my consumption is higher and with the fixed EGR cooler now its even higher.

I was thinking of cleaning the EGR and maybe align the valve with VCDS. I guess that will not help much?