Missfire under load on 01 4.3 blazer
 

When i put my foot in it the tach hits 3800 rpm, the tach goes crazy and it pings like crazy cant figure this one out already replaced complete fuel injection system injectors and all ,still getting missfire and crankshaft code

What codes are you getting? and what parts of the fuel system have you replaced so far?

crankshaft code and random missfire

oh ps the dealer replaced the whole injector system and the injectors they said it has a 10 year warranty on those parts

But what are the specific codes (Pxxxx)?

And I highly doubt that the injection spider has a 10year warranty.

let us know the code numbers, there were a handfull of conditions that could cause a random misfire and crank codes.

WELL the service writer told me that gm had some problems with injectors and that it has a technical service bulletin on the injectors and that it was covered ,I had a suburban and had the problem before and they fixed it but of course it was under factory warranty at the time

And im gonna have to get back with the exact codes,sorry but ill do it in the morning

Okay im back it was at the dealer and he says it may be an engine harness and it maybe not, so i got it home and it had two po304 codes and then i erased those and when in nuetral i reved it the tach goes whacking and jumps around and it had a po335 code ,oh and the dealer claims he replaced all injestors and the injector assmbly

If the tach is messing up, then it is possible that there is something affecting the CMP sensor (camshaft position sensor) or the CKP sensor (crankshaft position sensor).

P0335 and P0336 are quite similar codes:
P0335 - Crankshaft Position [CKP] Sensor A Circuit
P0336 - CKP (crankshaft position) Sensor Circuit A Range/Performance

If you are having trouble with the CKP sensor, it could definitely cause a misfire problem.

I want to thank you so much before i continue ,well ive tested the connectors im getting a light in the plug and the ground lit the light but then i got to the J35616-A test connector kit and dont have one of those and im wondering what the dmm is and if that stands for digital multi meter ,I have a digital multi tester ,and where would i get the test connector kit and the dmm,PS MY CRANKSHAFT WIRES ARE GREEN PURPLE AND YELLOW

I I need to start at the bigning it all started with a intake anti freeze leak this car has never had a check engine light on ,so i took it to a local shop for the intake gasket replacement after they fixed the intake i got on the freeway and it started to stumble when i tried to pass someone, I took it back to shop he claimed it has crankshaft code he replaced crankshaft sensor and its been to two dealers and no one can figure it out so here we are