Running Rich After Injector Replacement - SOLVED

[Kwing]

@JamisMG, my fuel pressure ran a rock steady at 58 psi before, during, and after my nightmare. I think the biggest variation window i saw from dataset to dataset was 0.2 psi. It was little enough to call it zero.

Where are you reading the 60? External gauge or with a tuner/diag tool from the ECU? If it's the ECU output, I would THINK the computer could adjust for extra 2 psi with less injector duty cycle. These other folks are much smarter than me and could say I'm totally full of it though, LOL.

 

[Marky Dissod]

I’ve read that regardless of regular 5.3L or Flex Fuel, anything over ~58 psi is too high.

Humbug. No reason to fear anything under 66psi / 4.5bar. More fuel pressure = better atomization.
What you need to be concerned with is a misreading of fuel pressure.

 

[JamisMG]

@JamisMG, my fuel pressure ran a rock steady at 58 psi before, during, and after my nightmare. I think the biggest variation window i saw from dataset to dataset was 0.2 psi. It was little enough to call it zero.

Where are you reading the 60? External gauge or with a tuner/diag tool from the ECU? If it's the ECU output, I would THINK the computer could adjust for extra 2 psi with less injector duty cycle. These other folks are much smarter than me and could say I'm totally full of it though, LOL.

On the mechanical gage at the rail I’m reading a steady 60 psi, but on the scanner I’m reading EXACTLY 57.9 psi and when I say “EXACTLY”, it does not budge or deviate even .1 of a difference at idle or any other throttle position. Just 57.9 all day long, which is weird because when I hooked up to an 07 Sierra it jumped around a little.

 

[Kwing]

On the mechanical gage at the rail I’m reading a steady 60 psi, but on the scanner I’m reading EXACTLY 57.9 psi and when I say “EXACTLY”, it does not budge or deviate even .1 of a difference at idle or any other throttle position. Just 57.9 all day long, which is weird because when I hooked up to an 07 Sierra it jumped around a little.

Oh these are gonna be dangerous words to say on the internet... I don't trust analog gauges for super precise readings. Just too much potential for human error, and I'm a pretty dumb human.

Yours could have a really large scale and small range on it that you can have confidence in a 2 psi delta, I obviously don't know, I'm just throwing that out there.

What you're describing on the ECU reading is consistent with what mine was showing. The bouncing you describe on your Sierra is the kind of behavior I would expect from a failing sensor or some kind of fuel system leak.

But take that with a pile of salt, because look how long it took me to figure mine out, LOL.

 

[Kwing]

I just had another thought. You said you're reading about -9.5% trim now vs the -25% you were seeing. Is that only at idle conditions?

I ask because that's about where my trim landed at idle at the end of this journey. At speed, the trims zeroed out, but the ~-9% at idle didn't seem bothersome to me as it was consistent and steady, and I didn't see big swings on the O2 outputs like I was before with the -25% trims.

 

[donjetman]

Fuel in the oil, from it running rich previously, can cause it to -9% from the fuel vapors being sucked thru the PCV system into the intake manifold. Drive it a lot, or change the oil/filter, to get it back to normal.

 

[Kwing]

Fuel in the oil, from it running rich previously, can cause it to -9% from the fuel vapors being sucked thru the PCV system into the intake manifold. Drive it a lot, or change the oil/filter, to get it back to normal.

Now there's something I hadn't thought of! I can absolutely see that, and I could see that thinning out the oil and contributing to my rocker noise I've been dealing with since I finished this.

I see an oil change in my near future

 

[donjetman]

There is a guy named Eric O. that has a YT channel called "South Mail Auto" that has done videos covering this situation, and a lot more.

His videos are entertaining and educational IMO.

 

[Fless]

There is a guy named Eric O. that has a YT channel called "South Mail Auto" that has done videos covering this situation, and a lot more.

His videos are entertaining and educational IMO.

South Main Auto LLC

Hey there viewers! My name is Eric O. and I own and operate a small town 3 bay shop in upstate NY. I grew up in the automotive industry (in my parents shop) and have over 25 years (working full time as a mechanic) experience repairing domestic and Asian cars and light trucks. This is all I've...

www.youtube.com