97 k1500 5.7 liter vortec misses on cylinders 3 and 5 while idling. about 1500 rpm only cylinder 3 and 4 miss then at 2000 rpm only cylinder 4 and 8 miss. what could cause this?

Very possible that it is coil pac also could be injector on 3 have it checked will cause problem with over fueling & reving

Well its not exactly ignition or fuel injectors, since cylinder 6 in in the firing order. 1-8-4-3-6-5-7-2
Could be something with the intake again, or the pickup in the distributor. I suppose if you have the multi-port injection inside the plenium it could be some of the spider valves or lines.
You would need to know if those cylinders are firing, and if they have normal compression.

The engine coolant temperature is high. Your other Codes are for missing cylinders on cylinder 1,2,3,and 4. Get the Codes cleared and start over. Changing the plugs and wires,etc could have generated the missing cylinder Codes.

Autozone,Advance, and Oreilys will scan for free.

Check your engine for an IDLE SPEED CONTROL SOLENOID, which may be in the intake. Or a fuel pressure regulator.

A lot of times people work on the spark side and forget the fuel injectors. They can cause a miss.

For engine misfiring problem check the help links mentioned below. Click the link below to go through the troubleshooting procedure :---- Engine misses and truck jumps? Hard to down shift? Issue with high gear only? http://technoanswers.blogspot.in/2012/02/engine-miss-and-truck-jumps-hard-to.html

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Bad miss at idle?

http://technoanswers.blogspot.com/2012/01/bad-miss-at-idle.html

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While stop engine idles like cylinder missing?

http://schematicsdiagram.blogspot.com/2012/01/while-stop-engine-idles-like-cylinder.html

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Engine Misfire codes for car?

http://schematicsdiagram.blogspot.com/2011/12/engine-misfire-codes-on-chevrolet.html
Engine Misfire codes?

http://schematicsdiagram.blogspot.com/2011/12/engine-misfire-codes-on-chevrolet.html

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Misfire on cylinder 4?

http://schematicsdiagram.blogspot.com/2011/12/misfire-on-cylinder-4.html

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Oil on spark plugs and car misfires?

http://technoanswers.blogspot.in/2012/02/oil-on-spark-plugs-and-car-misfires.html

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This will help.

Thanks.

For engine misfiring problem check the help links mentioned below. Click the link below to go through the troubleshooting procedure :---- Engine misses and truck jumps? Hard to down shift? Issue with high gear only? http://technoanswers.blogspot.in/2012/02/engine-miss-and-truck-jumps-hard-to.html

-----------
Bad miss at idle?

http://technoanswers.blogspot.com/2012/01/bad-miss-at-idle.html

-----------
While stop engine idles like cylinder missing?

http://schematicsdiagram.blogspot.com/2012/01/while-stop-engine-idles-like-cylinder.html

------------
Engine Misfire codes for car?

http://schematicsdiagram.blogspot.com/2011/12/engine-misfire-codes-on-chevrolet.html
Engine Misfire codes?

http://schematicsdiagram.blogspot.com/2011/12/engine-misfire-codes-on-chevrolet.html

--------------
Misfire on cylinder 4?

http://schematicsdiagram.blogspot.com/2011/12/misfire-on-cylinder-4.html

-----------
Oil on spark plugs and car misfires?

http://technoanswers.blogspot.in/2012/02/oil-on-spark-plugs-and-car-misfires.html

----------

This will help.

Thanks.

Does it miss at idle or going down the road, maybe both? Any applicable trouble codes? If you have that spider fuel system, I usually suspect that first. That system is noted for problems.
You could try a cylinder balance test, engine idling, you could kill the cylinders one at a time, quickly. If you kill a cylinder that has no effect on the idle, the cylinder is dead. Then you have to decide if problem is spark--fuel--compression on that cylinder.

just increase idle rating slightly...this will definitely solve your problem...

bad fuel pump can cause this or plugged fuel filter but i believe they are one unit

Did you by chance check the resistance of your plug wires? They have a tendency of breaking down over a period of time and need replaced. The spark plugs would have told you what was wrong with the engine many times.

third back pass side the coil is probably bad if you have a miss code common problem