Mazda Repair: Mazda Tribute rough engine/shudder, vacuum leaks, propane torch

Question
We have a 2001 Mazda Tribute V6 with 138,000 miles.  Bought it used at 110,000 in 2004.  Has always had the engine light on and has run roughly.  Now it has developed a very rough idle and shudders while driving around 45-50 mph, but will sometimes do it at slower speeds. It also stalls occassionally. The local mechanic seems to think we have a vacuum leak somewhere under the engine. We have also had a mechanic tell us that the cylinders 4,5 6 are misfiring.  Could this cause the symptoms and how costly could the remedy be?

Answer
a vacuum leak would cause the engine to shutter and sometimes stall yes and so could a misfire. cost is hard to say as i'm not the one fixing it and can't fully say what the problem could be.


quick check- if you have a propane torch you can open the valve (don't light it) run it over and around the engine if it idles high when passing by certain spots that would indicate a vacuum leak and give you a general idea where it's coming from.  however most vacuum leaks can be heard by listening for a hiss when the engine is running.