[mcosta73]

Hello Guys,

I've beeing having some intermitent sluggish performace from my auto transmission in the last 6 months, thought I had to take to an Auto Tansmission specialist.

Eventually I found that when I take off the Gas Cap (Diesil) and let the build up pressure come off the Gas Tank, the sluggish performece disapears and the transmission behaves like new.

Does anybody has a clue of what´s going on? VCDS does not show any errors.

Best Regards

 

[Fourdiesel]

Gas powered cars are required to contain the fuel fumes and react them in a charcoal cannister. Not the same with diesels.
The only function of a diesel fuel cap is to limit the vacuum which happens when fuel is pumped from the tank by the engine. [The cap also keeps dirt out.] If your fuel cap vacuum relief valve is not functioning, the fuel pressures and therefore flow from the tank could be too low. One of the symptoms of low fuel flow could be sluggish performance.
Try fitting a different cap - or leave cap off temporarily - and drive to see what happens.

 

[noobytoogy]

As above, sounds like a blocked/faulty breather on your fuel cap.