Hi, new to this site and need help badly. My son has a 2001 blazer with a 4.3. check engine light is on,codes read-po 300 random misfire. The tach also jumps at start up 0-3000 then drops back down to normal. I am thinking ignition module. I don't know anything about this engine asI am a Ford guy but any help would be greatly appreciated.-Okay I READ ABOUT code po 300 , I changed the crankshaft position sensor and the check engine light went out for about 20 miles.I read the codes and it is the same, random misfire and the tach is still jumping.What do we do next?

 

The P0300 code can be tough. Use the 'search' function for 'P0300' and read the threads we have concerning it. Let us know if you need further help.