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2003 gmc 3500 Savana 6.0 p0300



2003 gmc 6.0 3500 Savana.  Truck sit for a while ,first time driving it ran fine. After getting it legal a couple weeks later thrower code p0300 with rough idle no power Tested with test light for and have Injector pulse on all 8 cylinders.   Cylinders 2 ,7 both have no injector click with stethoscope, both have sparkplug spark. Fuel pressure at prime 58, running 54, holds at 52 .. I have freeze data from only an Acron  code reader as follows .   

.  Freeze frame data , throttle position 0.0% , RPM 630, Load value 5.4%, Air flow 15.52 gr/sec, map sensor 50, short term fuel trim1 0.0%, long term fuel trim1 0.0%. Short term trim2 0.0%, long term trim2 0.0%, short term 3  +50% , long term trim3  -36.3% , short term trim4  +57.0% , long term trim4  -45.2% , speed 0 , fuel system one and two open.   




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I don't know what's going on with that scan tool and the multiple fuel trims - makes no sense to me. I've never seen positive 57% fuel trim in my life!! That would be a HUGE air leak! By the same token, I've also never seen one read 0% at any point in closed loop. Not sure what the MAP at "50" is telling me, either. I don't know what to believe there with that data.


One thing that jumps out at me is your MAF grams per second is WAY off the charts high, though! You should be around 6 gr/sec at idle. I'd check the airbox for critters, and their nesting, seeds, nuts, an whatever else they carried in there. I'd wager a bunch of crap got sent through the MAF. Or, it could've failed without rhyme or reason - it happens, especially when they sit. Electronics are iffy on a good day. Add 23 years and extended periods being parked unused, and anything can happen.


If the injectors aren't clicking, you may want to see how the fuel is. You may have sent some ethanol-related goo into the injectors and plugged them up. If they don't click after a good cleaning, and you have injector pulse present, you'll need some new ones, unfortunately. Another way around that is to Google injector cleaning companies - there's quite a few out there across the Nation that'll rebuild or clean your original ones.

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