Long term and short term fuel trims intake leak, low idle, improving fuel mileage. Mpg

[afpj]

What does your maf read, in g/s, at idle? How old is the maf? The general consensus seems to be that the maf starts crapping out around 140k-160k miles without throwing codes.

 

[Burban22]

What does your maf read, in g/s, at idle? How old is the maf? The general consensus seems to be that the maf starts crapping out around 140k-160k miles without throwing codes.

MAF says Delphi in silver plaque on the side. Not sure if its original or has been replaced. Do I need to wait until it’s at operating temp or can I give readings during a cold start?

I have cleaned it a few months ago with the special cleaner spray. It looked clean but did it anyway since I was installing new cold air intake.

This burb used to have an oiled filter open box intake but I didn’t see any oil on maf. The filter always seemed like the oil dried up anyway. I went to a dry filter enclosed box intake.

 

[Burban22]

MAP Fluctuating between 7, 8 and 9. FYI I’m at 6900 ft elevation if that matters.

 

[Burban22]

MAF IDLE


MAF 2k rpm

 

[afpj]

I think it's best to take a MAF reading when it's warmed up, but the values for idle that you posted 0.6 3 lb per minute is about 4.8 grams per second. That's just slightly on the low side, especially considering your RPM is 602. My idle typically sits, after warmed up, round 550 to 560. I have a 5.3 flex fuel, stock. Not sure if you have the ability to borrow another MAF that's known to be good and see if your field trims still are that negative at idle.

 

[Burban22]

Update:
I cleaned my oem Delphi MAF with a q-tip soaked in crc maf cleaner. I gently rubbed the Q-tip on the intake side of each wire, and there was still a little fuzz and dirt built-up that I was able to remove since when you just spray the wires, you can only spray from the downflow side, not the upflow / intake side.

My long-term fuel trims are now -9 and -7 during idle and -4 to -8 driving.

When I have more time, I’ll try putting in the stock airbox instead of my cold air intake box maybe that is causing the negative fuel trims?

Recently went on a 400 mile road trip and got 16 - 17 miles per gallon driving 65 which seems really good for a 2003 suburban 5.3 4WD Z71 3:73 with 2” lift.

 

[Burban22]

Sending off all 8 injectiors to this cleaning service. Comes out to about $10 per injector. They don’t give flow rates or anything special but have good reviews and I’ll update if my LTFT improve from the -10 through -3 I’m currently seeing once they are clean and reinstalled.

FUEL INJECTOR ULTRASONIC CLEANING SERVICE - not for GDI injectors | eBay

Uniformity/Sprayability Test: To test the uniformity of injection amount of each injector and to monitor the spraying status of each injector with the help of backlight. This test is also for reverse flush.

www.ebay.com

 

[Fless]

When you get them back, a good bi-directional scanner can perform an injector balance test, along with a fuel pressure gauge.