I have a 2001 Elantra. The catalytic converter is 10 months old, the plugs are 5 months old and the wires are brand new. I just replaced the timing belt 2 weeks ago. I had to replace the plug wires because I was getting a #3 cylinder misfire code. Now the car is very sluggish and you have to floor it to go up hills and it has poor acceleration. I am also only getting about 20 mpg on the highway. could this be a coil problem?

 

I am also starting to second guess myself for some reason. The cam timing marks are hard to see eye level to match them up to the head. Could there be a possibility that I am off a tooth either way. Would it still run or would it bang valves? It is boggling my mind.

 

The Elantra does havean interference engine, but I bet being only one notch off would not result in piston-valve interference. It could be thebelt. If the problem appeared right when you changed out the belt, it's certainly worth checking.