ok hear it goes.. First off my truck is a 94 chevy z-71 it idels fine in park but when put into drive or rev. it starts to surge and miss. it contnues to get worse the long you set until the truck dies out and thenit willfire right back up. i delt with it up intel now and so i was going to FIX IT. to start i did the basics i changed the cap and rotor, fuel filter, map sensor, trp sensor, cleand the idle air control valve and rebuilt the throtle body. now it not only has the original problem but if you open the throtle slightly and hit a sweet spot the motor will surge spit and sputer like crazy. I also check the timming and it is right on the money but if i hold the throtle at that point and hit the timing light on it the mark is all over the place. I also noticed that if i unplug my egr selenod whal holding the throtle at this point the surging stops and the rpm's go up some and smooth out. It also spits and sputers when running down the high way weather the egr is pluged in or not. Any ideas would be greatly appriciated Thanks

 

Howdy, Have you had the pcm codes scaned, It might show something not flashing on thecheck engin light. free scans at most parts stores. The cat my also be cloged causing simular simptoms, Try replacing the EGR valve, carbon deposits can make them useless.

 

im going through the same thing put lots of money in the tune up the 4th and 5th cylenders are missing the intake gaskets are known to go bad and the springs in the injectors are faulty im working on that know in my 97