Hi guys I have an 89 chevy truck with a 350 tbi, i bought it a few months ago for a whopping 900$ it was horribly slow like i thought it was 4.3 at first and i was being gypped out of a 350, but all i had heard was how bad the heads are and how bad the cam is and all that so i thought nothing of it until it got a snazzy new misfire and surge so i checked plugs and wires cap and rotor all seemed to look relatively new like the previous owner was also hunting the miss down so i kept driving it and not knowing what the deal was replaced CTS and didnt help. I did however go blasting through a field in about a 6-8inches of snow when i drove back onto the road engine became really loud i thought i broke the exhaust but instead it was the cat that decided to explode i assume from having cold snow on it when it was so hot. i replaced the entire exhaust with shorty headers into stock y pipe and a flowmaster super 40. still felt wimpy and lame so i checked the timing it was wayyyy retarded brought it up to 1 advanced and got it to run good but then after a few days of running great it picked up a high rpm misfire so instead of throwing parts at it i decided to come here

 

at around what RPM does the misfire start to occur?An ignition coil going bad can cause a high RPM miss,but there are plenty of possible causes-I have only run early style HEI ,but I have heard the later separate coil HEI dizzy can develop a weak reluctor magnet-causing high-RPM miss.Non-ignition related possible causes include low fuel pressure,worn cam,weak valvesprings...

 

well i pulled map sensor off and it had 0 effect on the engine performance and i have the crescent guages with no tac and a 5 speed so basicly my butt and ears are the tac... thanks GM lol so i might try map sensor, but it just seems like ignition and not fuel

 

now it seems to have an annoying miss at random from very low to hi rpm but unless it is missing it other wise feels decent power wise. previous owner says it had new fuel pump put in not long ago and i believe him because the tank is a new plastic tank that is only about 24 gallons and long beds i think are 32 stock. so fuel i dont think is weak i have the ******* quarter in the regulator mod but it could have been low pressure and now its not as bad??? tried resetting the computer and no change, unplugged MAP and no change which is strange so now im leaing towards the pickup coil or Ignition module and possibly a MAP sensor also