i have a 2001 VW Jetta 1.8 Turbo GLS AWD. The problem started about 8 months ago. In the spring when I switched on my cars AC I found out that it was blowing hot air. So I took it to a mechanic who said freon pressure was low. On his recommendation I put in 2 small cans of freon. Turned out that the problem was not solved because the cars engine was heating at that time which was cutting off the AC but I only found about it later on. All the heating issues have been fixed by now. However when I switch on the AC I find that the AC is blowing cold air however I feel that the car's engine jerks every 30-40 seconds. I find it to be very scary while I am driving. Can anyone diagnose this problem and tell me what could be wrong here?