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.

so does this sound like a coil pack going/gone bad? 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 unnecessary stuff..

ALSO i swore i got a whiff of sulfur for a second while i was in the bed of the truck, as if it was a cat going bad, but i did have the 4 wheeler running, i've never smelled any sulfur like smells from the wheeler before, but i'm just not sure cuz it was brief.

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

 

[compleckz]

ok so i edited the first post, it is cylinders 1 and 4 misfiring.. also i just took it for a drive and came back, and i DEFINITELY smelled sulfur, looked under the truck, and my 2nd cat was glowing red (not very bright, but was glowing for sure).. this probably just means the misfiring is causing excess unburnt fuel to get into the exhaust, and heat up the cat..

i also went out and replaced the coil... its not the coil... lol

next?

 

[compleckz]

still no findings

 

[wheelie]

I have a 3.0L doing this right now. I checked the cylinders with a timing light, 4 of them stay firing, while two of them will randomly drop, causing a drop in engine RPM. I'm thinking its the coil pack.

 

[compleckz]

wish it were that easy for me.

 

[wheelie]

I threw another coil pack on, and a set of plugs, to no avail. Mine misfires about 20 seconds after startup. It is hitting on all 6 right after turning the ignition key, but then drops cylinders after that.

 

[redneckbrat]

mine is doing the same thing on #6, I'll be changing the wires too. I've got 140K on mine.

 

[compleckz]

mine ended up being the plug.. it still sparked, i verified this twice, but it ended up turning black after a few days of trying to figure out what the problem was (by running the engine).. so it was... partially fouled..

 

[AllanD]

another thing to look at when you have a misfiring EDIS engine is the contacts inside the coil "towers"

They can corrode inside on the wire contact leading to misfires.

AD

 

[redneckbrat]

I switched the plug on 6 and now it's 4 that is misfiring, swapped the wires and plugs on 4, 5 and 6; 4 is still misfiring.

 

[rangerrager]

maf?

 

[Hardwareman]

Please let me know what you guys find out as I'm having a hell of a time with this problem. Thank you.




Allen

 

[compleckz]

woah back from the dead!

anyways, i dont know what the problem is, my compression was consistent across the board-- but i've fouled the #4 spark plug 3 or 4 times now... it runs fine in between plugs fouling... its not my DD anymore, coolant isnt disappearing since i fixed a leaky heater valve.. oil is always fine... so i still havent really figured it out.