My engine developed a knocking sound and i had to take it to a mechanic. He had to dismantle the whole engine, after which he found out that it was the camshaft. I had to use the opportunity to replace the rings. A after coupling and mounting of the engine, the car only steams for like 2-3min and off on its own. He asked me to buy coil and new nuzzles, off which I did. But the problem persisted.
Had to tow the vehicle to another auto shop. The mechanic there said the number 3 plug does not pass current,hencing the car is missing fire. The steaming is now stable but once you engage the gear, the car offs. He has been on it for like 5weeks now, and I doubt if he knows what to do. Please I need help

Did you scan this car before allowing mechanic to dismantle the engine ?
Truth be told
Most mechanics just do trial n error and In a bid to solve a problem
They add to it

A lot of things can cause a car engine to misfire. The injector's oversupplying of fuel to the engine can cause misfiring. Secondly, if the injector coils are not receiving current it can also cause misfiring. Thirdly, this is the most unlikely cause, a faulty brain box (ECU) can just be the cause of the misfire. Warning: Do not ever allow any Machinic to work on the sensitive areas of your car without scanning.