Conversation Between bigdaddykane93 and oldfart49

first check your EGR valve to see if its stuck open from any small carbon particles. you can blow it out with some compressed air. then after that check your fuel pressure to see if its within specs. also check for vacuum leaks. and lastly check to see if your reluctor has slipped on the rotor shaft....

Just came across your post for the same problems i'm having on my 95jimmy on google, so i joined this forum to see if you or anyone else can help. I have the exact same problems and engine (vortec v-6) you had in your 8-21-2009 post, with negative ignition timing jumping all over the place. It came on suddenly-driving around the block and just like that, flashing check engine light and rough idle. On cold start up no light and no codes,but rough idle-then drive a block and engine light. No decent manuals on this but Haynes-So i've checked and replaced the spark plugs and wires-cleaned the cap and rotor-replaced the crankshaft position sensor (no resistance)-then the camshaft sensor in distibutor all with no luck. Am about to replace the right side knock sensor but i doubt if this will help. Have checked/cleaned all my grounds. Don't know where to go from here-think maybe my pcm needs reprograming but want to find out what you did, if i can. Work 6 to 5 so,i can't reply immediately