I had quite the problem with codes coming up as random misfires. I changed plugs, wires, rotor, cap, 02 sensors, map sensor, checked fuel pressure in the rail. After doing all this it still had a slight random misfire. I took the cap off that was only maybe a month old and noticed that on top of the rotor there is a little plastic elevated piece (tiny square piece) that catches the cap just a tad which causes the spark to jump around a bit. I bought new cap and rotor again to replace these and the new one had the elevated piece on it also. So I went ahead and cut it off and flush to the rotor and I have not had any other problems. No idea how i discovered this, just ran out of options so looked over the cap and rotor again and that was it!

 

Were these both delco cap and rotors, if not thay may have been the problem. The cheaper ones seem like a good idea when you are looking at your wallet, but they often use inferior metals in their contacts.

 

yeah they were duralast cap and rotors from autozone.

 

i have a 95 blazer 4.3, it had missfire on cylinder 4 at first so of course i changed the plugs and wires cap and rotor. than it still did it so i cleared the codes drove it and now it says multible missfire.. any ideas?

thanks james

 

after replacing ev erything on my blazer i found my p0300 was sticking valves on cyl 2 and 4 i caught it with a vacumn gauge and multiple compresion readings. i waitecd till the missing started and then did a compression test pulled the head sent it to machine shop and it runs like new again

 

1badblaze:::: did you have to do anythign special when reinstling the head after the shop went though it? I have a missfire on #5 and i think it's the valve since it's tapping like crazy (still have to do a compression check).I want to do myself since it's a second car but was curios about reinstalling the head.