Cylinder misfires, pulled codes, need advice.

[compleckz]

so for the past 6 months maybe, the truck on cold start has ran like it was misfiring for like maybe 20 seconds, if i revved it up a bit, it would go away quicker. it never did this again till it sat for over ~8hours.

today on my way home from a friends (700lb wheeler in the bed), it started running rough, stumbling, and i could hear like backfires in the intake when i got on the gas (i have a cowl-snorkel, so it was quite easy to hear)..

i was a mile from home, and when i arrived i unloaded the wheeler, checked over the engine, and couldnt find any apparent problems with the plug wires etc.. (they are 6-12 months old, along with the plugs)..

no CEL or codes, so i took it for a rip up the road and matted it (may not have been smart, but..) i got the CEL on, and got some codes, p0300 which is random cylinder misfire, and p0301 and po304, which are cylinders 1 and 4 misfire.

the only thing i have done is replace the coil (figured it was a good first step) and it did not fix the problem..

like i said before it did the same thing on cold start but very briefly, hopefully the sequence of events will enable someone to identify the part that has failed, so i dont go replacing new(ish) wires/plugs.. or more unnecessary stuff..

the 2nd cat was glowing red when i last drove it, and i could smell sulfur, but this is probably caused BY the misfire, not CAUSING the misfire.. but i'm not 100% sure of that..

this is a 97 OHV 4.0, 110k miles. thanks guys!

 

[MountaineerGreen]

Not sure, but could a clogged cat cause a missfire? If you had one glowing red, there is definitely a problem there. If your cat is clogged up, it can cause odd things.

It seems like you did everything correct to fix the missfire, plugs, wires, coil. The only other thing I'd suggest is pop the hood, fire it up and watch for arcing.

 

[compleckz]

clogged cat IS listed under a possible cause of the codes, but i think excess unburnt fuel (from 2 cyl's misfiring) entering the exhaust, would definitely cause the cat to heat up pretty quickly, im not sure if that would produce the sulfur smell though...

one thing that boggled my mind, is why did the 2ND cat heat up so much to turn read, but not the first (it wasnt red at all)... that makes me think it could be that cat.. i didnt notice if they were an assembly or not, maybe i can just pull the rear cat and see how it runs.. i doubt it though.

 

[MountaineerGreen]

You could cut out the second cat with a hacksaw and sleeve in a piece of pipe and clamp it in place. Don't know about MA emissions inspections though, you could get in big trouble for removing it.

My unscientific opinion is that the second cat is clogged, the first one should do the same but worse if it was unburned fuel, since it's not, a bad cat is my guess.

I had a 90 Ranger with no downstream 02 sensors, my cat was so clogged up, the truck barely ran. It was a bolt in piece, I unbolted it, knocked out the guts and put it back. Ran like new then.