Need Help!

[EcoBoostN]

Been having issues with my st running lean when off throttle, otherwise the numbers seem to be good. LTFTs will go up to 13%, AFR values will spike to 40% when lifting off throttle to brake for a second or two then go back to normal.

Have an intercooler, intake, exhaust and stage two Cobb tune. If you could help me out in regards to this issue that would be great.

 

[Jabbit]

Start by replacing your Cobb tune with a custom tune by TunePlus, Dizzy, or a tuner of your choice. Do you see the same numbers when running on the stock tune? I'm not sure how much faith I'd put in any numbers reported by the AP for AFR instead of a true wideband afr gauge.

 

[EcoBoostN]

So I went back to a stock tune and the good news is the LTFTs are at 0, but I'm still getting spikes from the AFR. Not sure if that's something to worry about or not.

Here's a picture of the access port data.

 

[EcoBoostN]

Well the LTFT data must have not been calculating or something as its back up to 13%.

 

[Erick_V]

The AFR's going to 40+ after lifting is normal. You aren't on the gas, therefore no gas is being injected and it's "lean". Log/monitor the STFT at WOT and it should hover close to 0%. Generally +-5% is ok. Also, the LTFT is an average number over time, if you flashed a new map the ECU now has to relearn the fueling trims. If it is still hopping around after 20-30 miles you likely have a leak somewhere

 

[EcoBoostN]

Would an exhaust leak potentially cause a lean fuel mixture, if it's before the primary oxygen sensor. Been told that I had an exhaust leak before I put the new exhaust on.