Help ! At our wits end !

[MeanGreen01]

Hello ! 

 

I have a 2001 Silverado 1500 HD 6.0 the truck started running rough out out of the blue and is showing a code for cylinder 2 &7. We have replaced Plugs, Wires, Coil Packs, fuel regulator & fuel pump.  injectors have been checkd and thats not a problem either. We are still only getting 45 pounds of pressure With everything replaced. What else could it be ?! 

[Formulabruce]

Buy some Throttle body Cleaner, Clean ( Surgically clean) the throttle and plate, both sides spotless. ( remove the big hose clamp on front and wiggle it off the throttle. This should help a lot with the roughness. Check the MAF sensor while you have it off ( on your left on the air intake hose as you face the engine.). 45 lbs does sound a bit low as I recall, BUt I would clean the throttle and area first. Do NOT use CARB cleaner...

[riverbanks]

You said,"still" for pressure,old pump and new,same readings?and when are you reading it?key on,engine off,,idle,,also try with vacuum line unhooked to regulator,see if it jumps up at idle

[riverbanks]

More thinking,can you verify the guage?try on another vehicle,see if it's reading the proper pressure? just thinking it's off,you should have a 300 code and probably a 02 code(s) if entire system is low,not just 2 cylinders,you read codes? scanner or just reader? 

[SILVER SLED]

Try relearning the crankshaft position sensor. 

[carkhz316]

Have you checked live data? What are the fuel trims or O2 voltages indicating. If rich or lean, this will give you a direction to go in determining if it's a fuel or ignition related misfire.