Wont start sometimes and when it does it wont idle.Runs fine at a rev but when you let off the gas pedal to idle it dies

From your description, most likely there is a problem with the Idle Air Control (IAC) valve. Its job is to open at idle to let air in when the throttle is closed. Either it is clogged, or it has gone bad. You will need to remove it and clean it, or replace it. It is bolted to the rear of the intake manifold. When you remove it, try starting the engine with the valve removed so air can get in the intake. If the engine idles ok, you'll know that the IAC was causing the problem.

Another possibility is a leak in the vacuum system. With the engine running, listen closely for any tell-tale hissing sound. Inspect all the vacuum hoses and the air intake duct, and repair as needed.