Could be a few things.
Temp 2, Broken wire or bad connector at temp 2 
sensor. Does it run well when cold then crappy 
once warm. It will use allot of fuel if the ecu 
thinks the engine is cold. Temp 2 lets it know 
its warm and to lean it out a bit. I was only 
getting 14mpg till I found the broken wire then it shot up to 21mpg.
It was intermittent so it was a bear to find. 
Also O2 sensor or air leak on the exhaust before the O2.
Have fun!

Good luck
Jonce

>Hi ,
>
>
>
>I have a 1983.5 watercooled vanagon with a 
>little problem..  I normally have a decent gas 
>consumption but on my last day out, the van used 
>twice the gas consumption as usual with a loss of power.
>
>
>
>Does someone had the same problem and can enlightened me?
>
>
>
>
>
>Thanks
>
>
>
>Pierre
>
>
> 
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