My 95 4.3 vortec blazer wont idle after its warmed up

The older model vortec engines needed more fuel pressure than 60psi to run. You might want to verify the min amount for your model. Have you replaced the fuel filter recently ? Is the check engine light coming on ?

metal box mounted in front of coil.

I can be problem with IAC valve or motor,or there can be vacuum leak issue it its dirty Idle control valve or problem with dirt build up in throttle body.Click this link below and follow step by step troubleshooting:-----http://whatisbyme.blogspot.in/2012/05/high-idle-on-chevy-blazer.html
---------------this should help.Thanks.

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check the vacuum lines on the engine.sometimes these will crack or develop a small hole or break and it will **** too much air in the engine causing it to act that way.

Check the tps "trottle positioning sensor, on mine the idle would not stay steady, and shift so hard that it would sound like it was going to break something. it is located on the drivers side of the throttle body with a push in electrical connector.

Get the codes pulled, often an oil change place has all of the adapters. You need to know what the computer thinks is wrong, before you do anything.

Shakes how? While stopping? Or solely while idle, Engine light on?

If if shakes while stopping you need to check you're wheel hubs and or Suspension ,

Shakes at a light, You may have a bad fuel Injector, Check you're psi in you're fuel pump, A TPS would cause low idle or sometimes high idle, With low idle and a bad motor mount it would shake,

I know theres a few things I'm missing but,.. I have a major Headache atm so I'll get back to you with some more, when i can think better. :)

nothing ..normal low pressure at idle while hot ...but really should be thinking fresh oil change and filter soon..also what are the RPM's at idle hot in gear with A/C radio and other accessories running?

check your Throttle Positioning sensor that should fix your rough idle the TPS controls the breather on the front of the engine its affixed to the right hand side of the throttle body just infront of the spyder on the V6 Vortec 4.3L Models