Hey everyone.

I wrote about this issue back in July 

My car has a strange issue with a rough idle and a hot engine smell

After a long drive I can smell a hot acrid burning smell in the cabin

The exhaust note drops noticeably however only at idle

The car can vibrate ever so slightly too when returning to idle from higher rpms

I have run diagnostics with no faults, and the car was seen by a VAG specialist garage

I changed the EGR valve 5 months ago due to this issue and the problem seemed to resolve

It is however now back, just not as bad at this time. 

My thoughts? Could the EGR valve have gone again?

The electric mechanism of the last one seemed faulty and it was fully of black oil, likely the seal around the valve actuator arm had decayed. I'm not sure however why the new one would fail too.

Seems the hot smell and sound happen more after applying the brakes hard

The exhaust note may change slightly when the brake pedal is pressed too

I wonder if a vaccum leak is actually the problem somewhere near the brake booster.

 

Any ideas please share!

Many Thanks 

Luey 

A vacuum leak sounds a plausible explanation for the rough idling if you have a petrol engine because servo vacuum is drawn from the intake manifold. (Diesels have a combined fuel/vacuum pump for the servo.) Whether that would also explain an EGR problem I do not know.

What surprises me is engine fumes are getting into the cabin. Modern car ventilation ducts are usually well sealed from the engine bay.

Sorry if it wasn't clear I put the engine model in the title. It's a 2.0 TDI 170 (Engine code BMN).

So I guess a vaccum leak is a real possibility, or potentially the fuel / vaccum pump is failing. 

I really can't tell you what the fumes are sometimes it smells like burning oil, other times just smells hot, and others it smells like exhaust/diesel

1 hour ago, Luey said:

Sorry if it wasn't clear I put the engine model in the title. It's a 2.0 TDI 170 (Engine code BMN).

So you did. Sorry, I didn't notice the TDI, though I must admit that many of the letters and numbers used to describe models by all manufacturers are meaningless to me.