The car's speed decreases as the engine warms up.

[Jossan]

I have a Corolla Verso from 2005.
The car's speed decreases as the engine warms up.
I can not accelerate and the gas pedal does not seem to react.
I have changed the fuel filter but that did not help.
Any suggestions?

[Jiff]

I'm no mechanic or expert, but could it be the air filter? It may not have sufficient oxygen to burn the fuel properly, or maybe the auto choke is stuck, presuming it has one. 

Not sure why it would change as the engine heats up though.