I have a 1998 Chevy k1500 5.0L Vortec. It began having a problem where it would jerk intermittently while i was driving and when at stoplights or very low rpm's the engine would turn off on me. It would turn off after it idled erraticly, dropping low and raising up again, but would start right back up immediately and have no problems for a little while. That can be "fixed" by giving it a little gas while keeping on the brake at a stoplight. I replaced the fuel filter in august, got a new fuel pump in December, and had a tune up done this past month. It runs better after the tune up but i still have the problem. The service engine soon light is constantly on and I have tried three different code readers on it and none of them were able to connect and get a reading. I have no clue what to do with it anymore.

 

Check the fuse for the cigarette lighter if it is blown the diagnostic port won't connect. That is going to be you best friend in a situation like this.

 

First thing is you need to find out why the CEL is coming on.
Even if it means paying a shop for diagnostic time.