#5 Cylinder Miss, Bad Wire?
 

I have a 99 Jimmy with a 96 4.3 engine. It is showing a 0305 code for #5 cylinder misfire. I used an ohm meter set at 20K and got a reading on the #5 wire of 2.26. All the other wires ranged from 5.72 to 6.69. I hooked a plug up to the wire and ran the engine with the plug grounded. The spark was orange with a little blue at times, but did not crack when fired. All the plugs on this side of the engine are a little sooty while the ones on the other side appear normal. The engine will have a very noticeable miss, but at times it ALMOST goes away and runs quite well, the check engine light will go off when it starts running better, then it will come back the next time you start it.

Does the reading I got show a faulty plug wire?

I also noticed tonight that the K and N filter the previous owner installed is a bit too short to fit properly in the air cleaner housing, so I am guessing the Mass Airflow Sensor is probably dirty and in need of cleaning. I don't know if this could contribute to the one bank running too rich or not as I am new to working on anything newer than a 70 Mustang. Also, I should mention that I have installed new plugs, distributor cap and rotor all AC Delco.

I love this truck and have been reading posts like crazy on this wonderful forum, but thought it was time to ask you guys for some help. Thank you in advance.

here is one thing you can to to see if the plug wire is bad, When its dark, start the truck, and spray around that side with a water bottle (mist) and see if you see any sparking from the wire being bad.

if the wire is not bad, check the cap and rotor, there could be corrosion on the #5 causing it...

ALSO, pull the #5 and see what the plug looks like, if possible, take a photo and post it on the site.

I will try the water mist idea tonight after work. I just put a new cap and rotor on it, so I would think it was in good shape. The old cap was corroded and the rotor was in sad shape. I pulled the plug last night and found it to be black and sooty as were the other plugs from that side of the engine. They were replaced a short time ago too. The other side of the engine looked normal.

I misted the wires tonight with no light show. I bought a tester today that looks like a spark plug with a clip on it to ground it. The spark was bright blue as it should be and it matched up with the other plug wires when I tested them. I switched plugs out with one I knew was working properly and no change, still has the 0305 code. The plugs on the drivers side are all sooty, but #5 is the only one with a miss. The other plugs look normal on the passenger side. I took a picture and in the picture the plug looks a little shiny, but it is not, it is a dull dusty looking black. I rented a fuel pressure tester and a compression tester and will do that tomorrow afternoon. I don't think it can be spark at this point, so it will be one of the others. When I first got the truck it had been sitting for some time and threw all kinds of codes. I changed the plugs, distributor cap and rotor and got a 0300 random misfire and 02 voltage low code. I drove it for a while with some seafoam in it and the light would go off, run well, then back on again. Now it has the 0305. At least it keeps getting better in the code department. :)