AutoMD ... 5/7/2014
2003 Ford Explorer Sport Trac XLS 6 Cyl 4.00L
The engine misses. Have been told it is the timing chain or belt or cracked head. They say have to replace e
engine. It occurs all the time. No engine light comes on. Could it be electrical.
I believe your vehicle is equipped with a timing chain. How many miles are on it? Strange that the PCM isn't picking up on any misfires. I would do two things to determine what the issue might be. First I would perform a compression test. Along with that check that all fuses and relays are working. Check all cylinders for spark. Check all fuel injectors to make sure they are not plugged or open/shorted. If your engine is the ohc type, I would also pull off one or both of the valve covers and inspect the timing chain. If the chain or tensioners (if equipped with tensioners) are worn, the chain will have slack in it. If the chain has too much slack, your mechanical timing will be advanced too much (the relation of the pistons to the valves opening and closing).