I have a 1997 chevy blazer with 4.3 litre vortec engine with a troble code p0300 (random cylider misfire).I am having problems with localizing this problem.This is what i have done so far:new plugs,cap,rotor,wires,coil,pcv valve,air filter.Nothing has worked so far.Ill tell you exactly what it is doing.First of all it is very random.It mostly occurs at freeway speeds above 50 m.p.h..It is more of a jerking kind of feeling.I know that it is missing and not backfiring.Lately it has been getting worse.Now it sputters upon takeoff and threw normal street driving.Last week the service engine soon light came on.I bought a code scanner with the ability to get live data and the trouble code was p0300(random cylinder misfire)and that was it.I dont know if this helps or not but the other day i noticed when i turned the radio to a weak fm station i could hear a tick that sounded like a plug wire was touching ground but later on that night i went to a very dark place and looked under the hood while engine was running and i couldnt find any sparks.I know that is not a fullproof way of checking plug wires.I also with the engine running removed one at a time the plug wires and the engine responded negatively every time so i know it is not specific.Im thinking it is probably a fuel delivery problem and not an ignition problem.My question is where do i go from here???

 

Have a look at this, if you have not done so already https://blazerforum.com/forum/showth...0300+explained, you can search p0300 and it will bring up a bunch of posts

 

I had the same prob. with my 2000 blazer lt, i replaced the distributer and problem solved. Distributor is 125 without the core, and its the best money i have spent in a long time! hope this helps! also just for the heck of it change out all your spark plugs, you wouldnt believe the difference it makes!

 

These are high performance engines. You must use high quality replacement parts. I had the same problem, came down to a cheap distribuator cap/rotor, and faulty spark plug wires, Both brand new, mid priced items from Autozone. Fork over the dough and buy from the dealer, also get the right spark plugs, thses are ewually as critical.

You could spend the $80 and have the dealer diagnose the problem, I did and thats how I found out what was wrong. My parts swapping missiion was a huge waste of time and money.

 

I agree with Hanr3 you should usually spend the money to get OEM. but on the other hand, not everyone can truely afford that. But in my opinion i think you would be so surprised if you replaced you distributor, and distributor cap, also plug wires and spark plugs. again i had the same problem and sure enough that problem is GONE!! Try it out!

 

i have a 2000 blazer ls and its reading the P0304 cylinder 4 miss and P0507 idle air control ive replaced wires cap rotor fuel mass delivery box as well as all new injectors im stuck im too the point where i just wanna sell it.... whats the easiest way to drop the tranny any tricks i should know?

 

P0304 is piston 4 misfiring. Swap plug wires and plugs with another piston that is working prperly and see if the code moves to the new plug. If mot you may have a fualty ICM, take it to autozone and have them test it.

As for the tranny, start a new post or check the TECH section, pretty sure there is a TECH thread on dropping the tranny, and yes there are tricks to it.