Please help with this 4 out of 8 cylinders

[hidroela]

I just replace the heads on my 5.7 vortec engine
And when put every thing back only cylinders 3748
Works a means work because when you pull the
spark plug while the engine is running you fill when
a cylinder is working or not
also when I put the scanner it shows code
p012
p300
p1345

please any help would be appreciated

[SpitAndDirt]

Are you sure that the first is P012 and not somthing esle? If you forgot a 0 and the code is P0120, that means: Throttle Position Sensor/Switch A Circuit Malfunction
Code P0300 means:Random/Multiple Cylinder Misfire Detected
And code P1345 means:SGC (Cam Position) Sensor Circuit Malfunction/ Crankshaft Position - Camshaft Position Correlation
Hope this helps- Chris

[SpitAndDirt]

One last item, you need to have your timing set by the dealer unfortunately. If you disturbed the distributor, it needs to be electronically reset. -Chris

[hidroela]

Please brother you were right de code is p0102 and why you say that I have to take the car to the shark dealer is that timing deal that hard or difficult to do, there are not a
Procedure to do that

[SpitAndDirt]

No there is not a way for the normal everyday shadetree mechanic to set the distributor timing. If you did not mark the location of the distributor before removing it, the computer does not know the position you reinstalled it. The GM Tech 2 Scan Tool and possibly the Snap-On scan tool are the only ways to communicate to the computer that the distributor has been moved. The computer has to be told that it needs to relearn the position of the distributor. As for your code of P0102, it means: Mass or Volume Air Flow Circuit Low Input Hope this helps. -Chris

[hidroela]

Chris I really appreciated you’re advice you drop me a bouquet of cool water because now a need to deal with this guys that most off the time are just a part replacement they don’t care any ways they don’t pay for it. Ones a gain thanks you very much

[GMMerlin]

Originally Posted by hidroela

I just replace the heads on my 5.7 vortec engine
And when put every thing back only cylinders 3748
Works a means work because when you pull the
spark plug while the engine is running you fill when
a cylinder is working or not
also when I put the scanner it shows code
p012
p300
p1345

please any help would be appreciated

First I would have the camshaft offset adjusted (reason for your 1345 code) this will have to be done by someone who has a bi-directional scan tool...spec is 0 degrees at 1200 rpm.
On the P0300 code and only 4 cylinders firing, if the misfire is not corrected by the distibutor adjustment, I would check the rocker arm adjustment...they may be a little tight....although the book says 1 turn, I perfer to remove the lash and go 3/4 of a turn..works every time.