hello good day, a few days ago the truck is failing me, it is a peugeot partner 2000. engine 1.8. It goes out in the traffic lights both CNG and gasoline and regulates poorly in low. In high it goes well. Suddenly you come walking and when you slow down you regulate unstable and stop. cold at the beginning and now hot too. What can be? I saw that the butterfly of the carburetor is quite black but I do not know how to clean it, I had been told that there was a product to clean that spray. I do not know how to detect if it is an electrical problem or the passage of gasoline. I thought about the step by step but they told me to clean it before changing it. Thank you