I have 96 silverado 1500 5.0 4x4. I did a tune up..plugs, wires, cap, rotor, air filter... when I put everthing back together and started the truck. The CEL came on and I noticed I forgot to plug the sensor plugs for the air filter back in, when I pluged them in the light went away. After a day or two the CEL started to blink (P0301)..It has been mifiring ever since in cyl#1. Did a compression test and all was fine in that respect. I changed the fuel filter and re-replaced the cap and rotor just in case it was bad, no change. Im stumped! We did do one other thing because I have spark in all plugs we pinched the fuel return line closed about half way, when we did this the misfire went away. Any ideas would be awesome..

 

What does the plug look like? Swap plugs, if no change swap plug wire from 1 to whatever, does the problem stay, or move to the swapped cylinder?

 

We have tried all that. Same thing. The problem always stays in cylinder 1. We also had it on a computer and used a camra scope to check the cylinder and it look fine. Ive been told that it could be a dirty MAF or dirty EGR. I of course want to do the cheapiest things first before I just rip into it to replace the spider injectors and intake gasket. As that is exspensive and a pain in the a**. It also makes a faint sound of an exhaust leak or a tick. Not sure if its a leak or just because the cylinder isn't firing..

 

Skawt youtube is a great place to find out how to do the expensive yourself...I pulled my plenum myself and checked the injectors about 45 bucks each if you need any not a bad job gaskets were 30 bucks and a few you don't need unless you are doing the entire intake...my plight was 40 lbs on cyl six so I scrapped my 240k 4.3l but the larger engines are the same my brother and I did the job in 4 hrs...unless its a major exhaust leak won't cause a misfire code...do you have a p0300 code as well the random misfire code? that could be the fuel pressure regulator located at the back of the spider...if you pull the plenum pull the no.1 injector and turn on the key if gas comes out it is not supposed to...the injector is bad...while you have it apart make sure you remove the egr valve clean and lubricate it and clean the egr tube between the valve and the intake...its the top hole and the tube is usually brass but may not be they get carbon clogged up something awful...that's all I have for you most of this can be found as I said on youtube...and you can do a baby powder leak test or a cigar works as well locating vac leaks you will see where it sucks it in...good luck Al 2nd 2500 ps make sure to clean your maf but if you're not getting that code it's working but maybe not good enough be careful spraying around the sensor itself it's in the very center of the screen and spray from the rear

 

Thanks for the info. Ill try the baby powder trick. I am really thinking that its a clogged poppet. The truck pretty much runs great despite the misfire, which is soooo FRUSTRATING!!!!