Thanks to this forum..I am really confused now

[jpnanda]

I have a 86 300E 5 Spd.my center vent stopped blowing air...I checked the threads here and found out that it could be because of the Vaccum Valves go bad or tear so one does not have the same vaccum ( which should be around 25) or if the climate control was not working properly..today I took my car to a mechanic and he checked the car and told me that my 4th cylinder was not working properly and my problem could be because of that. So I need to get my engine repaired before he can even fix my problem and even after getting that fixed he cannot telling me if my problem will be fixed as I may need new climate control unit and/or the valves..so I am looking at an expense of over $3000 still not knowing if the problem will be solved or not...any suggestions ..I need to take my car in on Fri if I need my engine done..thanks for all the help

By the way what effect does having the bad 4th cylinder have or what symptons..as my car runs fine..no stalling, no problem with power, no smoke, no shuttering..idle or in low speeds, so how can I say that theh cylinder or the valve there is really shot