Originally Posted by Jetdoc
Most likely the timing belt is one notch off.
Here is a tip for timing the engine.
Remove the spark plugs! Set the drivers side cam pulley right on the timing mark, set the pass. side cam pulley on the timing mark then rotate the pully towards the engine about 1/2 of a tooth. Set the crankshaft right on the timing mark. Install the belt starting at the crankshaft then tensioner the pass. cam pulley ect.. Loosen the tensioner bolt to allow the tensioner to tighten the belt then tighten it back. Rotate the engine through 6 times and check the timing marks, they should be right on. Loosen the tensioner bolt again and retighten it.
I had trouble with this until I used the 1/2 tooth tip.
Here is a good thread for timing belt help
I just finished a the head gasket job. I got my car started but it is running rough and backfiring slightly. So I'm guessing it is the timing. How far should I break it down to get the timing right? Removing the cam sprocket shields or removing the entire cover and putting the belt on from scratch? My passenger side cam sprocket does not have a timing mark so I made a best guess.