is it egr valve???

Can a egr valve gone bad cause my 4.3 vortec 1997 jump and chug like crazy at idle and driving(well cant really drive to see ,its that bad)MIL on to.???

sounds like your plug(s) have some carbon build up on them. If you have not replace them go ahead. If you have just pull them out and chip off the build up. Try not to use gas cleaner all the time.
Good luck Mango

The EGR can cause those problems, but before guessing at problems, you need to get the codes read. Autozone will read them for free. If you can't drive it to autozone, they have a loaner scan tool that you can get. Just give them about $200 and when you're done they will give the money back.

Ive done that and have only got a p0300 multiple misfire code?

You can try cleaning the EGR valve, use a new gasket when you put it back on. That probably isn't the problem though. When was the last time you did a tune-up?

In the last two months I have changed:
plugs(platinums)
wires(buash)
tps
cap
rotor button
ignition switch (wire harness)
air filter
gas filter
oil change new filter
tranny flush
new water pump

And after all of this my truck was running sweet. Then at a stop light it missed once,twice and then started jumping all over the place?? MIL light came on and started blinking. I stopped had it towed and now it sits in the garage?

The Egr valve was the problem for my dads s-10(4.3) engine to run that way. When the truck is running and the hood is open, does the engine vibrate a lot? It happened to my dads truck. Got the egr valve replaced and that fixed it. Also this was about 2 or 3 yeas ago, so that is the same amount of years your truck is (yours is '97, my dads is '95.).

Sorry I can't tell you any more. I do know the EGR valve was quite costly.

OHH, you may also want to ask this over at www.s-series.org . They seem to know there stuff over there.

egr will cause it to jump and buck. i cleaned mine and havent had a problem with it since. easy to do. and saves on the wallet too.

just had a thought. did you dissconnect your battery while working or replacing electrical parts? if not you might try to reset your computer by dissconnecting your neg bat cable for about 10 min. see if that helps.

I have a 93 with a 4.3 that idles rough at stop lights.

I just bought it so I don't know what has been changed on it or when the last tune up was.

I got a code key from auto zone and all it gives me is a code 12 over and over again.

what is the deal?

Check The Haynes Manual. It Tells Ya In There, The Code 12 Will Flash 3 Times, Hesitate, Then The Next Flash Sequence Is The Code You Want To Look At. If It Only Shows Code 12, The Computer Is Not Seeing Any Codes.no Problems There.
THE CODES THAT THESE DAMN S-10`S GIVE ARE EITHER OF 3 THINGS.
1. NOCODE.
2. INCORRECT INFORMATION.
3. ABSOLUTLY CORRECT.
ELECTRONICS PLAY MUCH TO BIG A PART IN LETTING AN OTHERWISE GOOD RUNNING ENGINE, LOOK BAD, OR, TOTALY CONFUSSES THE AVERAGE JOHN Q. PUBLIC INTO BELEIVEING HE HAS A VERY SERIOUS PROBLEM, WHICH , MORE OFTEN THAN NOT, IT ISN`T.
IF THERE IS A SPARK, AND THERE IS GASOLINE, THERE IS SURE AS HELL GONNA BE A FIRE.
WHAT WAS WRONG WITH POINTS AND CONDENSERS? AND CARBURATORS? AND A SIMPLE AMOUNT OF UNDERSTANDING?
USED TO BE WITH A FEW TOOLS, AND A HALF A BRAIN, YOU COULD FIX A VEHICLE ON THE SIDE OF THE ROAD IN A FEW MINUTES, OR, AT LEAST KNOW WHAT WAS WRONG, WITHOUT PAYING JOE GREASE MONKEY A FAT LOAD OF CASH TO GET THE OLD HEAP GOING.
AH, YES, 1960, I REMEMBER IT WELL.

I have a 93 with a 4.3 that idles rough at stop lights.

I just bought it so I don't know what has been changed on it or when the last tune up was.

I got a code key from auto zone and all it gives me is a code 12 over and over again.

what is the deal?

EGR valve needs to be cleaned and reinstalled with a new EGR valve gasket.

Do a complete tuneup.