2005 GMC 1500 with 2007 Silverado 1500 5.3L Injector/MAF issues

[Ahp5054]

Hey HPTuners Community:

Got a quick question for you guys/gals. Has anyone ever had issues with a Gen 3 to Gen 3 motor swap, meaning the 2005 GMC 1500 needed a new motor so a rebuilt 2007 Silverado 5.3L was purchased and installed. When I open up stock maps for both motors I noticed the tables are different indicating different PCMs I would assume. My question is pretty simple, what is the stock fuel injector flow rate for a 2005 GMC Sierra 1500, same thing for the 2007 Silverado 1500. To my knowledge the Silverado was NOT a flex fuel vehicle so it does not have the flex fuel injectors. The customer did however tell me that the Reman'd engine came with 28lb/hr injectors. But out of all the stock injectors I tried to look up through various forums I have yet to see conclusive answers stating the 07 Silverado 1500 uses 28lb.hr injectors.

Also a secondary possible issue, do the 2005 Sierra 1500 and 2007 Silverado 1500 have the same MAF sensor? I'm assuming not.


If all else fails, and the information isn't available, can't I just uplug the MAF tune the VE tables in openloop with the wide band, then replug the MAF back in and rescale the MAF?


Thanks for any help in advanced,

Tony

[2xLS1]

Be more specific about the 2007 They made both Classics and NNBS trucks that year and there is a big difference between the two. You say Gen 3 to Gen 3 and between those two there would be very little difference between them. Same injectors and MAF as long as one is not flex. Even if one was a L33.

[Ahp5054]

Reman'd engine sheet shows a 28lb/hr injector though, so do you believe this was a typo? If they are truly the same motor id assume just using the base calibration for the Sierra 1500 would function correctly but it doesn't. I am seeing issues on hot starts and car is also running rich. I will see if I can get some logs down and post them, but as far as PCMs go I know that the 2007 Silverado has different tables for example 07's use Pressure differentials for injectors calcs while 05 Sierra uses just MAP pressure. I'm sure its something simple I just need to log and alter I just don't want to get way over my head and fight a losing battle using the stock GMC sierra calibration.

[2xLS1]

You are comparing a NNBS calibration to a Classic.

[IARLLC]

Where mention opening up maps/tables for both engines, where are you getting your info for the 2007? As mentioned 2007 had both "Classic" (GEN3) and GEN4 Silverados so if you get a factory 2007 tune from the HPTuners repository there is pretty decent chance that it is a GEN4 tune. Maybe you already knew that but I thought it was worth mentioning.

If I remember correctly normal 2005 5.3s had 24.6 lbs/hr injectors and Flex had 33 lbs/hr injectors. I can't remember when the pressure control system changed over but it seems to me the Flex systems continued to use the old style return a few years after the non-Flex had gone to returnless. I can't see why a rebuilder would use 28 lbs/hr injectors unless it was ordered for some performance application. If they installed non-factory injectors...they should provide injector flow info...but that seems very strange as they could never count on a given buyer to have the ability to tune for bigger injectors. Maybe the GEN4 5.3 had 28 lbs/hr injectors. Not sure on that. Can you get the part number off of one of the injectors? It will help a great deal in narrowing down correct flow rate info.

[Ahp5054]

Ohhhhh ok I see what you were saying now. Yeah the tune off of the depositary is a Gen 4 hence why the tables look different. As to why they used a 28lb injector I have no idea. Ill see if I can get ahold of the parts number on the injectors and work from there.

But with that in mind the tuning process should be the same as if it was the stock motor(except change injector scaling for the larger injectors): Put the car into open loop disconnect MAF and tune the VE tables with a wideband, when VE tables are set replug in the MAF an calibrate the MAF.


Thanks for the clarifications.

[IARLLC]

One thing to mention. On this set-up you should not unplug the MAF. The IAT is in the sensor and it will tune weird thinking the outside air is -40...
Better to fail the MAF by going to Engine Diag>DTC and setting the MAF codes P0101, P0102, P0103 to "MIL on first error".
Then you go to Engine Diag>Airflow and set MAF Frequency Fail High to 0Hz. This guarantees that the MAF will fail.
Please don't completely disable the codes or the MAF will not give you SD mode.
Then under Engine>Spark>Main Spark Advance copy your high octane table to your low octane table because in SD the computer uses the low octane table.
I then prefer to go to Fuel>Power Enrichment and set MAP to 90%, reducing the chance of PE during SD tuning but keeping it there for full throttle if needed. Some like to turn it off completely for SD tuning and some who use a wide-band prefer to leave it alone.

Good luck!

[Ahp5054]

Completely forgot about the integrated IAT. Ok thanks for all your help, ill get on that probably tomorrow.

But my logic is correct, do SD open loop tuning first, then once that is finalized with all fuel trims hovering around 0 to -4% I can replug in the MAF, reenable the normal High freq fail and tune the MAF Freq in open loop using the same wideband method done with the VE Tables.

Thanks For All Your Help!!!!

[IARLLC]

Yeah. All sounds good. It sounds like most prefer to tune SD then MAF. That is how I usually do it. Some of the experts suggest MAF then SD and have reasons for that. There are cases where the fuel trims are way off and the client is going to take the car home for the night so I make a quick change to the MAF for obvious/immediate improvements...but in the end the result should be the same.

[Ahp5054]

Ok awesome! And I got to the bottom of the injectors. They were tested at a different Fuel pressure then OEM injectors so when I rescaled them it wasn't to the new injector tested pressure it was to the OEM rated pressure which the new injectors were tested 43.5psi so they were off by a nice margin.

[IARLLC]

WOW! 28 lbs/hr at 43.5psi! Up at your pressure they must be moving quite a bit more fuel.

[Ahp5054]

Stock fuel pressure is 58psi I believe. Need to double check that in the morning.

[IARLLC]

That is what came to mind for me. I bet you are getting a good bit more than 28lbs/hr.

Seems illogical for them to show a flow rating for a pressure that is way below later GEN3 pressures.