Mis fire 300

[racerkyle]

Hi, I have a 1996 GMC Z-71. Some of you may remember me from 4 or 5 months ago. I was told by dealership that they could not find what is causing the misfire code. We have done seems like everything. Anyways, I won't go into all of that, but my tranny doesn't go into lock up all the time, still! Not even half the time. But transmission guy says that the computer is not telling the transmission to go into lock up. So misfire code is causing that problem. Anyways, now I'm having a EGR Valve code now, not all the time, but when it comes on, I use my hypertech programmer to clear codes, then it may come back on a mile down the road. Could this cause my misfire, but I would think that I would get a EGR Valve code instead of a misfire. What do you all think. Also my fuel mileage has dropped about .5 to 1 mpg. Atleast the last 2 or 3 fill ups. Thanks!

[budhayes3]

If the EGR valve is sticking open, it will create a vacuum leak. Maybe the PCM is seeing a percent of misfire from that. A couple of folks have had some decent luck with removing the valve and cleaning it. It's worth a shot.