Fluctuating Air-to-Fuel Ratio

[Nadomokos]

Hey guys... my air to fuel ratio always fluctuates between 13.8 and 14.3 at idle or when cruising. Nothing seems to be wrong with the car. I'm just curious if this is normal. I have a 2016 ecoboost mustang with a BBK 3 in off-road downpipe, a Magnaflow competition series catback, and Cobb CAI, a Mishimoto performance intercooler, Mishimoto catch can, and a stage 3 OTS tune from Cobb. Do I need a pro tune or is this normal? Thanks in advance !

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[jbailer]

While cruising, that is fine. At idle, it should be holding very close to optimal depending on what fuel you're running. If you need a tune, you should be getting a CEL. The tune would be required if your A/F needed adjusting because it had pushed the fuel trims as far as the table in the COBB S3 tune would go, there's no more room for adjustment and the WBO2 sensors are still detecting an undesirable A/F.

The fuel trims are something you can monitor with the COBB AP3. Take a look at the short term and long term. Persistent ST will adjust the LT. When they reach the threshold, it should give a CEL. That is of course if COBB didn't disable the WBO2 to keep it from throwing codes which is entirely possible.

Personally, I would just go to Adam @ Tune + with your mod level. You'll be much happier with the results and it will be tuned for your car, not generic. That COBB S3 tune hasn't had the best press if you know what I mean...

 

[ronv95]

make sure there is no exhaust leak at your downpipe

 

[Nadomokos]

While cruising, that is fine. At idle, it should be holding very close to optimal depending on what fuel you're running. If you need a tune, you should be getting a CEL. The tune would be required if your A/F needed adjusting because it had pushed the fuel trims as far as the table in the COBB S3 tune would go, there's no more room for adjustment and the WBO2 sensors are still detecting an undesirable A/F.

The fuel trims are something you can monitor with the COBB AP3. Take a look at the short term and long term. Persistent ST will adjust the LT. When they reach the threshold, it should give a CEL. That is of course if COBB didn't disable the WBO2 to keep it from throwing codes which is entirely possible.

Personally, I would just go to Adam @ Tune + with your mod level. You'll be much happier with the results and it will be tuned for your car, not generic. That COBB S3 tune hasn't had the best press if you know what I mean...

Hey I actually spoke to Adam today. He said what I was experiencing is normal. I'm getting new charge piping and a upgraded BOV. After that I'll definitely get a tune from Adam!

 

[jbailer]

Hey I actually spoke to Adam today. He said what I was experiencing is normal. I'm getting new charge piping and a upgraded BOV. After that I'll definitely get a tune from Adam!

Awesome, you're going to love it!

 

[Nadomokos]

make sure there is no exhaust leak at your downpipe

Hey, I took it to the shop that installed the downpipe and they said there weren't any leaks.

 

[Skeezin]

I have similar mods 3" turboback, JLT intake, map ic. and I tried running the COBB stage 3 tune and I was running lean also 13-13.5 at idle. I had CEL on as well. I had to go back to my unleashed tune.

 

[Nadomokos]

I have similar mods 3" turboback, JLT intake, map ic. and I tried running the COBB stage 3 tune and I was running lean also 13-13.5 at idle. I had CEL on as well. I had to go back to my unleashed tune.

Well I'm not getting a CEL it just fluctuates between 13.9-14.1. The only time it's gotten lower then 13 is on accel.

 

[Juben]

13-13.5 at idle is rich.

On 93 pump, 13.9-14.1 is COMPLETELY normal. There's zero reason to be concerned with that.

 

[Nadomokos]

13-13.5 at idle is rich.

On 93 pump, 13.9-14.1 is COMPLETELY normal. There's zero reason to be concerned with that.

Okay cool thanks man... any reason why it would bounce down to low 13s in stop in go traffic? It only goes that low for maybe a second before going back to 14.1

 

[jbailer]

And the 13.9-14.1 should be for e10 which is most gas stations 93. With no ethanol at all, it should be near 14.7

 

[Nadomokos]

And the 13.9-14.1 should be for e10 which is most gas stations 93. With no ethanol at all, it should be near 14.7

Okay cool thanks! By the way, do you know of any gas stations that are actually ethanol free? Maybe shell's V-Plus gas or whatever it is called?

 

[jbailer]

Okay cool thanks! By the way, do you know of any gas stations that are actually ethanol free? Maybe shell's V-Plus gas or whatever it is called?

Not all Shell stations are ethanol free but Shell is one of the few around me that doesn't use ethanol. The best way is to jut look at the gas pump itself. Somewhere in all that crap they write all over it will say.

 

[Tune+]

I have similar mods 3" turboback, JLT intake, map ic. and I tried running the COBB stage 3 tune and I was running lean also 13-13.5 at idle. I had CEL on as well. I had to go back to my unleashed tune.

Well, having a CEL could be the reason and that is rich not lean. Lower the number, the richer the fuel mixture.

 

[Nadomokos]

Not all Shell stations are ethanol free but Shell is one of the few around me that doesn't use ethanol. The best way is to jut look at the gas pump itself. Somewhere in all that crap they write all over it will say.

Oh cool I'll keep an eye out for ethanol free

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