Hi I have a 95 Cherokee with the 4.0 ho and a msd street fire and after 3 days of mud bogging it started misfiring. We originally figured the cap and rotor got wet and muddy but when I checked them they were clean so I went to the plugs and pulled cylinder 3 at random and the plug was melted. So after I figured I'll pull and check the others 1246 had high speed glazing 3 and 5 were melted. Last night I put some autolite platinums in and today my buddy and I were trying to figure out what was going on and I showed him plugs 3&5 and ask to see the new 5 and it was OK so I pulled 3 and it was started melting. I wanted to know what direction to start in.

 

Are you running factory gap?

 

Yes the .035 that is posted on the firewall

 

Hotter coil open up your gap. Try opening up to.045 and see how that works to start. The instructions on the coil should give some info if not try the (800)# and talk to MSD. A hot rod shop of any sort should be able to help.
Last hot coil I ran was a MALLORY Uni-lite had to open my gap to.068 from .045 on my camero.

 

Its a msd street fire box

 

+1

Curious if you need to switch to colder plugs.

 

First thing I would do is, Get rid of the msd crap coil. They are over rated pieces of garbage. Put a stock coil and some good old Champion copper plugs gaped at .035 and I bet your problem will be gone.

 

It's the stock coil the msd in just the ignition box so we could lower the rev limit cause I already broke the valve spring once on over rev in the woods

 

Can u post some pics of the plugs?

 

Cylinder 3 is top and 5 is bottom

 

Sorry about that. I thought you had the MSD Coil.

 

Same

 

To my eye that looks fouled, not melted.

 

Kinda what I was thinking as well. Don't recall ever seeing a melted spark plug.

 

I'd still say get rid of that MSD box and your problem will go away. What's the point?