I have a 1998 s10 blazer that has been misfiring. It had been idling slightly rough. I was on the highway and everything seemed fine and all of the sudden rpms dropped and speed dropped. I pulled over and it was idling very rough. Code said random/multiple misfire. I replaced the wires, plugs and cap and this took care of the extremely rough idle. It still idled slightly rough though. Starts fine. I had to replace the intake gasket a couple months ago. When i had the wires replaced they didn't say they were wet or anything. They said a couple of the plugs were pretty burnt. If coolant was leaking into the motor wouldn't it be smoking? I'm just not sure what to try next. I had the light come on today again after having a coolant flush down. I checked it and it said random misfire and misfire on 4. That light has now went off again though. Any ideas?

 

Check fuel pressure and leakdown. These engines rely heavily on correct fuel pressure, if it's only a few psi low, it can cause performance issues including misfire DTC's. https://blazerforum.com/forum/showthread.php?t=45941

"If coolant was leaking into the motor wouldn't it be smoking?" It depends where it is leaking. If the intakes are leaking internally, coolant doesn't necessarily leak into the combustion chamber. It usually leaks into the crankcase, in which case there would be no smoke, just ruined engine bearings if not repaired in a timely fashion.