1993 z28 lt1, 6speed 58k. as of a couple of months ago my cars running rough when i first start my car up its seems ok until the car drops idle, then it starts idleing all over the place bogs down then the idle jumps up all of a sudden to about 2k then back down. when the car warms up it idles off seems like its running ok but i think it has a little miss not to sure though. im going crazy trying to figure this out some one please help, p.s. ive changed the optispark, plugs,wires,EGR vavle, evap solonoid o2 sensors, ran fuel system cleaning through system, im going crazy jake z28..........

 

maybe the timing is messed up?

 

Is your SES light on?

 

no the cars not throwing any lights at all.

 

does anybody else have any ideas still stumped. i did notice that when i start the car it runs fine for about 1 to 2mins and then all of a sudden it sounds like a switch kicks on and makes a high pitch noise under the hood and then the car starts running rough, idel drops and it like starts to bog and all of a sudden the idel jumps over 2k and then drops back down and starts bogging again, please help...........jake z28

 

Ignition system? You check that yet?

 

no i have not, i replaced ignition switch back in july because of the secerty light kept comming on and it wont even let me start the car. but how do think the ignition would have any thing to do with whats going on with my car

 

idk, my waterpump leaked onto my opti and caused all kinds of problems.

 

i replaced my optispark back in july and replaced water pump to because i had take it off to replace optispark, i guess it could of went bad again but that would suck, water pump not showing any signs of leaking though............. jake z28

 

I had some similiar problems two years ago. It turned out to a blocked catalytic converter. You may also want to investigate a bad ignition coil.. they go bad along with the wire. Other folks have had problems with fuel pumps which can lower the fuel pressure at the rail.