I was offered a 2005 TB with the 4.2 engine. The car has at least one known problem- somebody replaced the spark plug of cylinder # 5 incorrectly, and probably damaged the threads. Also, the bolt of the coil of the same cylinder is broken. They "repaired" the car somehow, by fabricating an aluminum "bridge" between the coils # 4 and 6 to fix the coil # 5 in place. The car starts but the engine runs with a misfire. The owner stopped to use this car several months ago and now he wants to sell it. We checked the misfire data; there are multiple (about 40-50 in one minute) misfires in cylinder # 4 (not 5!). I am thinking about buying this car. I think I can remove and repair the broken coil and the plug together with my friend. I will extract the broken bolt and use a Heli-coil to repair the threads of the plug. However, I afraid that even after fixing, there are some chances that the engine will misfire. The truck has the LPG (propane) setup installed on it. The LPG itself is known to cause the excessive wear of the valves. What do you think, guys, what are the chances that the engine is screwed up?