Hey, I just recently started getting a missfire on the truck. I had replaced the plugs with NGK tr6s gapped at .040 and some new Napa wires.

It ran fine for a while, but then all the sudden it started missing quite a bit. You can really feel it at about 2k rpm especially in 5th gear.

I plugged the Snap on Modis to it and was getting random misfires on every cylinder, but 2 and 5 had the most.

I checked the wires, #2 doesn't "click" onto the coil, and #5 came off the plug real easy. I pushed the #5 on tighter and tried to get the #2 to stay on tight, and it still drove the same.

While driving around and trying to stay at 2k the CEL came on,
Catalyst efficiency low.(can't remember what bank)

What do you guys think is going on, is the miss messing up the O2's or are the O2's giving me a miss??

The plugs and wires have about 8k on them, had about 4k when it started missing.

Any Thoughts??
Thanks

 

The misfire could have done the cat in...do you still have your stock wires to swap on and try?

 

Check your wires to see if the headers are melting them.

 

I am going with failing cat converters. Unbolt your exhaust and look at the substrate, tell us what you see.

 

check the porcelain on your plugs you probably cracked one of 2 when u put them in.... very common

 

Stock wires are gone, those damn metal shield/springs never come off nicely...


All the wires are fine, I still have the stock manifolds

I did drop one plug when installing, but it was on cylinder 1....

I was going to get another set of plugs, and wires and see what happens.

Have people had any better luck with some MSD wires over what I get at Napa. Also how is the .040 gap on the NGK TR6 for a supercharged 6l

I've been thinking for a while now that I might have some Cat issues, I just haven't really wanted to tear the whole exhaust apart, just spent $850 on a new clutch and pedal assembly because I was too cheap to buy a good clutch last summer... and if I do tear the exhaust apart LTs are going in, but I'm at 94% IDC right now, so I'm gonna need new injectors to do LTs....it never ends

 

True, clogged cats will cause misfires...

 

Hey man ive had the same problem with my 01 2500HD it would miss like crazy and shoot 02 and cat codes i replaced everything from wires plugs even cats and it ended up being corrosion build up with the hook up into the pcm i got a new pcm and recrimped the female ends on the harness and problem solved just look at the leads to see if they have and corrosion

 

Seven post about misfires, and not one of you mention it being a personal problem.

 

since it happen after installing plugs and wires im going to say thats your problem. IMO oem wires are the best and the ngk plugs are good but check if one is cracked.