99 chevy pickup 1st start of day is fine, but if it sits for longer than 10 min. is hard to start, Idles rough?

99 chevy pickup 1st start of every day is fine but then every start after is hard if it sits for longer than 10 minutes, idles rough but runs fine when you are driving. Have replaced some things like fuel filter, plugs and wires.Any suggestions?
The SES light is on, the code was random misfire.
There is sometimes a sulfur smell also.

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3 Responses to 99 chevy pickup 1st start of day is fine, but if it sits for longer than 10 min. is hard to start, Idles rough?

  1. bandit_60 October 2, 2010 at 10:36 pm #

    check the fuel pump. it sounds like it,s losing it,s prime. or the gas cap might not be holding the pressure.

  2. tronary October 2, 2010 at 10:36 pm #

    Try some injector cleaner. Sounds like you have at least one injector leaking when engine is off.

  3. Wes October 2, 2010 at 10:36 pm #

    You did not mention a check engine light, so I will assume you have no trouble codes. Your fuel metering valve may be bad or going bad, it is located under your upper plenum(manifold). I cannot tell you here how to test it, it takes diagnostic equipment like at the dealer. It may not be supplying necessary fuel to cylinders.

    Unfortunately, the cost of this unit is close to $400.

    I had a similar problem on my 1996, but figured it out on my own even after paying through the nose at a dealership.