I was riding my 99 Honda shadow vlx. After giving it some throttle to pass a vehicle it died and would not start. Then once I finally got it to start it will idle but dies as soon as I throttle. What could be causing this?

If a carburetor, the float may need setting as it may be starving for fuel .

How did you check the petcock? sure its not that.Yeah swap coil packs then ask again.

From your description you can be fairly certain it is an electronic problem.

I had a similar problem once with my Honda CX500. I found the connections to the ignition module had gone green and a good clean up restored normal running.

check fuel.check battery.spark plugs will 1/cylinder at the top of head.remove insulated lead by hand and you'll see plug.match plug by noting brand and number written on the plug or take it with you to parts supplier.if cleaning use gauge available at auto/hardware store and be sure to match gap (find specs online).when reinstalling, don't overtighten.

This could be two things:
1. A stuck throttle grip. With the bike off and stopped, twist the grip and see if it snaps back into place. If it stops, but you can "push" it back into place - you have a stuck throttle. It's not idling. It's stuck "on".

2. Adjust the Idle. Typically, there is a little daisy wheel next to the throttle grip and you can turn it left / right to adjust the throttle.

Battery probably! did it push start? because if it did,,,, you should continue to ride it for awhile to recharge the battery.... that is if the voltage regulator is working o.k. check battery voltage, if its only 12v the regulator is probably going out.

use a thin piece of wire and clean the ilde port and transfer port if that doesn't clear it up check idle jet

Check fuel pump. You might have a bad diaphragm.