Misfire problems

[corn322]

Ok, I finally got tired of trying to figure this out, mostly due to lack of warm, sunny saturdays.

My '93 240 has a strange misfire problem. Started about in november. It won't start to misfire untill after it has been warmed up for about 5-10 minutes. It will misfire occasionaly at idle, and when it is bad it will misfire at regular intervals, like once a second. While driving, it will be fine unless I push the gas pedal past about 1/4 the way down. Then it will bog down, and it sounds like one cylinder isn't firing.

spark plugs: denso plat. about 11 month old/~10k mileswires : whatever autozone had, not bottom line, but not top line, same agecap rotor : whatever autozone had, same ageMSD A6 + Blaster coil : about 1 month old, thought problem was bad coil.

[Dirtylou]

The KA in my truck does that when the ignitor gets wet, but only when it rains. Does it happen when its dry outside?

[corn322]

yeah, it happens rain or shine

[ricebike]

i'm just guessing...

mebbe the MSD coil is wearing out the platinum plugs prematurely???

higher voltage+ lower voltage plugs= quicker erosion/ bigger plug gap sooner...

might haveta pull plugs to verify & just use either high end iridiums for extended life...

regular copper plugs (ie Bosch super/ regular ngks) & change 'em out every year

ps: doesn't hurt to recheck the ohms on the plug wires... & do a visual on the not-so-top-o-the-line cap/rotor set...

cap/rotor have brass terminals like pepboys borg/warner select products? not the cheapo aluminum alloy terminals...

finally: i don't have FSM for that vehicle (mines a 89 sohc) but those books have a great troubleshooting tree to follow...

[corn322]

problem started long before I got the MSD stuff. I pulled the cap and rotor when I installed the MSD a month ago, normal wear, but within limits.

also, I was too tired to remember somethign I wanted to put in the first post:One day it was idling bad, I decided to pull the injectors one by one to see if they had any affect on it. Cyl. 3 seemed to make it stop, so I left it unplugged for about 5 minutes with the engine running. Plugged it back in and the misfire prob was gone for the rest of the day.