AFR for 01 3.4 supercharged

Hello, Recently I've had this issue where my AFR are 15.1ish while cruising. Ive already changed the MAF in the last year and did the AFR sensor this weekend. Weird part is if I unplug the battery the first drive it runs perfect, 14.5. Second trip it runs lean.

 

Fuel economy unlocked.

 

15.1 AFR while you’re in boost? Problem.
Not in boost? No problem.

What fuel system upgrades do you have?

 

Well I figured it out. For reference, the truck always ran 14.3 to 14.6 out of boost cruising. It ended up being the fuel pump. I assume it was weak causing it to run slightly lean and intermittently drop out.

 

Nice, what did you upgrade the pump to? Running stock injectors?

If you do tune it, sounds like you can gain a lot of efficiency while out of boost. No need to be 14.3 in low load/no boost, that’s much too rich.

 

I went with a Deatschwerks dw100, no need for any bigger on-stock injectors. For reference I'm running 33s with stock gears so there's a decent amount of load on the engine. Id rather run rich than too lean. Espcially going down the highway a little extra fuel would do some good to keep things cool.

 

Sounds good. Just keep an eye on carbon build up and plug fouling, that’s a lot of unburned fuel over time.

 

Sounds good I'll probably do plugs every 30k along with the SC belt. Should probably move removing the front cat up the to-do list. Not too worried about carbon build-up. The water-methanol seems to be doing a great job cleaning everything up.

 

Oh yeah the meth will steam clean everything lol

 

Just to circle back what is considered safe AFR for highway cruising. I'm seeing 14.4 to 15.2 while cruising now.

 

@Speedytech7 will have better input than I will. 15.1/15.2 should be safe under low load/low boost, however if that’s with stock ECU and you just changed the fuel pump I’d be a little concerned because it’s not programmed to let the truck run lean like that, so there might be something else going on.

 

If you're tuning for it appropriately then 15.2-15.6 is acceptable but it just ending up there on its own is concerning

 

I will try to get some video of my afr going down the road. Yeah that's what I was thinking. I might grab the scantool and see what the oem afr sensor is reading.

 

What should a factory ecu be at?

 

Here is a video accelerating up to 40mph then cruising at 1800rpm. I notice that sometimes the wide band will go rich for a second then flip back to reading lean.
https://youtube.com/shorts/ju0cU6TDl14?si=JlpLu2WolcLpGuMK

 

14.7 +/- .2

 

So I'm running slightly too lean. Any ideas on what might cause that?

 

OEM AFR is a narrowband sensor, it is not accurate outside of a pretty narrow range.

14.7

That’s accelerating, in boost? Do you have a boost gauge? There’s almost no fuel enrichment, not sure if you just weren’t getting on it or what. Even moderate boost, 2-3 psi, you should see AFR drop to the low 14’s.

 

Where is the AFR sensor located in the exhaust stream?

 

The boost gauge is the number above the afr gauge. No I wasn't really getting on it. If I hit boost the methonal will force it rich. My concern is cruising.The wide band is placed right next to the factory sensor.