random misfire code p0300
 

my 96 blazer has a random misfire code that i am having trouble diagnosing. i have checked various possible causes such as the spark plugs distributor cap fuel pressure, sprayed brakeleen around the intake manifold, and tested for spark at cylinder 1. when i unplugged the wire at the cylinder the engine seemed to run a little better. the main problem is cant seem to let the engine idle because once the rpms get any lower than 650 or so it stalls and shuts off. the ignition module and coil have been changed recently, and the previous owner states that he has changed the cap and rotor along with the plugs already. but i am unsure of his rliability and have been advised to just go buy a new set anyway. i am on my way to purchase those parts, howver assuming that changing them does nothing what's everyone else think? the problem is grinding up my flywheel and burnin out starters because of the engine buckin around at start up.
p.s. the ggas pedal has to be held down for the engine to fire up. otherwise you just get backfire and what sounds kind of like detonation.

read this ... this can prob help you

P030x - Random/Multiple Cylinder Misfire Detected

I found this using the search feature

Id do a nice tune up to it ... Its possible the previous owner must of used aftermarket products
these trucks prefer ac delco ignition products you can also run ngk plugs if you want ...

tune up is a success
 

thanks for the reply. the engine is running a lot better after the new plugs rotor cap and cables were replaced. now im on to finish the tune up with changing the fuel filter and oil with a good ol coolant swap. it still has a rough idle. but i'm sure i can figure that one out. thanks again!

glad shes running better

something that can cause rough idle is the maf sensor

warm the engine up to operating temp then disconnect it

if she runs good clean the maf ... you can get maf cleaner at your auto parts

the maf is good and clean. i took a look at it in the process of pullin hair from the misfire issue... i changed the ckp a bit ago, and wasnt sure if not doing the crankshaft position relearn process would cause this problem, but niether a tech 2 or modis have the option to do it...