Ok so my car started to miss fire so I changed plugs and wires, AC Delco Gaped at .45 then and the wires are MSD 8.5s. It still was missing and I changed my opti and coil mew GM unit on the distributer and an O'Reillys unit on the coil. It is Still Missing on one F***ing cylender except every once in a while it will kick in on all 8 but then go back to 7. It never runs on all 8 more than a few minutes. So WTF could it be

Thanks

 

You're positive it's a spark issue and not an fuel injector? Also you should try taking off a valve cover and make sure valve train on that cylinder is functioning correctly and nothing is amiss. Also a compression test wouldnt be a bad idea.

 

try LIGHTLY tapping on the fuel injectors with a screw driver or something, that usually will get them to unstick aslong as there not too bad. Id also recommend the GM in tank fuel injector cleaner. Its a little more then an off the wall brand, but it works very well.

 

To rule out the injector, you can swap it to another cylinder. If the misfire follows to that cylinder, then you know you have an issue with the injector.