I have another problem. It has to do with A/C. I tried posting it at other place but nobody replied so I am posting it here.
About 6 months ago my car's A/C was blowing hot air and that was just before the summer. So I took the car to a mechanic and he said that freon pressure was low. On his recommendation I put in two small cans of freon. (Ohh by the way, now I feel that mechanics was no good). Putting 2 cans of freon didn't solve the problem. Later on I found out at a car shop that Jetta's AC system gets disabled when engine gets hot. It was because my water pump's plastic impeller blade was broken. Anyway recently I got all heating related problems fixed along with new timing and serpentine belt replaced. Now I have noticed that when I switch on A/C the car starts jerking on regular intervals while I am driving. I can really feel the surge in the engine almost every 30-40 seconds when I driving the car and I find it scary. The A/C is blowing cold air though.
So what could be the reason for the engine surge or jerk every 30-40 seconds? How can it be fixed?