05 GT A/F Ratio and SCT BDX Tune Question

[CobraR980]

Hey all - trying to help a buddy out on a car he recently purchased...has an 05 mustang GT with a fairly modified 4.6 (cams, long tubes, cobrajet intake and all the goodies that go with that) and has been noticing his A/F ratio sitting around 18'ish at idle. On throttle it's back down to what I consider normal, in the 12-14 range but unless all the other mods somehow make an 18 normal, i think that's pretty lean, no?

Second part of the question, assuming the above is "iffy", probably should have the tune looked at imo. Previous owner said he had it all tuned using an SCT BDX with a tune from Lito. All in quotes here haha, but previous owner didn't give him the SCT BDX. My experience is with an S550, but doesn't he need the SCT BDX since it holds the stock tune in order to build a tune off of that? Or can he just buy another SCT BDX (or any tuner?) and pull the current tune and data log from that?

If we're going in the wrong direction in thought - i'm open to what ya'll think.

 

[JC SSP]

What are you using to read A/F? Any pinging? Have you looked at the spark plugs? Check the vacuum with a gauge, it might have a leak.

Contact Leto and see if the VIN is cataloged. All you need is a tuner to download old tune and upload a new one.

 

[CobraR980]

Previous owner has one of those triple gauge pods on the top dash with an autometer cobalt wideband. Assuming it's installed correctly haha, but have to track through everything. Next step was going to check the base of the intake for any leaks.

Thanks for the direction!

 

[EBABlacknChrome]

I would definitely check headers/collectors for leaks first, then see what's happening, then email lito. He will definitely need to buy an SCT hand held. 18 is way lean but could be an exhaust leak.

Sent from my SM-G996U using Tapatalk

 

[Juice]

Log idle and see what the adaptives are. LTFT and STFT.
Idle is closed loop and should be right around 14.x. Having a wideband read 18+ means one of two things: it is not accurate or, its just a matter of time before the CEL comes on.
An exhaust leak before the wideband O2 will do exactly whatyou are describing, lean idle reading and normal reading while driving.
SCT does not use a "read" from the pcm. They supply a stock file to build the tune from. A tune is not VIN locked, the device is. If you want to go back to stock, have a dealer flash it. I see no need for that.

 

[moooosestang]

How can you be sure the cobalt gauge is setup correctly? What wideband is it? It's not just a simple plug and play process, there's math involved.

 

[TomL]

At idle the gauge should read around 14.7+/- as the fuel trims are constantly being corrected by the pcm. You probably have a vacuum leak since the ratio improves as rpms go up. You don't need to have the pcm reflashed by the dealer. When I bought my 05 it had cams but didn't have the tuner included. I bought a Bama RevX/BDX and saved the tune it had as the stock tune. If your friend decides to get a BDX, I will sell mine because I went boosted and had to get an X4 because the BDX won't log certain PIDs(DMRs). Lito did my N/A tune and is doing the Boosted tune at this time.

 

[RocketcarX]

Autometer widebands are garbage. Get an AEM X-Series.

What do the OEM oxygen sensors show at idle?

SCT devices overwrite tunes. No return to stock needed