Hi,
the blue plastic piece cap on the front of the engine to the right end, what is that? I am missing that cap on my car?

http://i.ebayimg.com/00/$T2eC16F,!zo...UwWfIQ~~_4.JPG

 

It just covers the fuel pressure Schrader valve. A valve stem cap from a tire valve stem will work.

 

[QUOTE=liweih21;353643]Hi,
the blue plastic piece cap on the front of the engine to the right end, what is that? I am missing that cap on my car?

It's on the left of the engine bay. Everything on a car is left and right in relation to sitting in the car, not standing in front of the engine.

And yes like ES6T said, you can use a tire valve stem cap to cover it.

 

ok, i used a wheel tire cap to cover it fits ok.
so it appears there wasn't one there before or someone removed it,
what effect does that occur when nothing is cover that pressure point?

 

The cap serves the same purpose in both positions, tire or fuel rail. It's just to keep dirt out of the valve. The valve is what holds the pressure.