Air/fuel ratio spiking in a new Mustang, sometimes losing power. - Ford Mustang Forum
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post #1 of 33 (permalink) Old 02-04-2013 Thread Starter
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Air/fuel ratio spiking in a new Mustang, sometimes losing power.

This is the air/fuel ratio on a 2013 Mustang GT with about 600 miles on it, under moderate load (upshifting through the gears while coming to speed on the highway).

Its been giving me trouble in that the ratio will shoot up, causing the check engine light to blink and engine to lose power.

That did not happen in the period depicted here. Nonetheless, this seems way too volatile for me. Can anyone tell me how normal this is?

Even if this data looks OK, can anyone share any experiences with the problem described above of high AFR/power loss randomly happening in a practically new car?

I'll try and get a sample when the engine starts losing power and will post when/if I have it.



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post #2 of 33 (permalink) Old 02-04-2013
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Have you pulled the code? Each instance that I have seen a blinking CEL, it was a misfire, which would explain the power loss.


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post #3 of 33 (permalink) Old 02-04-2013
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Have you pulled the code? Each instance that I have seen a blinking CEL, it was a misfire, which would explain the power loss.

I agree, and the change in A/F ratio could be the result of an issue rather than the cause. The commanded A/F changes constantly with load and other factors so unless you are datalogging the car for tuning purposes there isn't really a reason to watch it.

If your check engine light comes on your only option is to have it properly diagnosed at the dealer because we can't do anything for you.
 
post #4 of 33 (permalink) Old 02-04-2013
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It's normal for your AFR to bounce up and down. Its a moving target so it will never stay solid. Just remember that part throttle and idle is always going to command stoich which is 14.1 for the 2013 and I believe it's the same for all coyotes. Wot is going to be anywhere from 11.9 to 12.3 or at least mine was stock and I have a 2013. When you let off throttle it's going to cut fuel to save gas and you will see your AFR go super lean. This is all normal.

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post #5 of 33 (permalink) Old 02-04-2013 Thread Starter
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OBD test results

So I've both pulled codes and taken it to the dealer.

The dealer was useless, and basically said they didn't see any codes, and therefore they couldn't do anything.

This got me paranoid, so I bought a OBD/bluetooth reader and installed Torque Pro (which is where the data came from).

Torque also shows no codes, but it does show some errors when going through its test suite. Some seem relevant, so I'm posting below:

O2 Heater Monitor Bank 4 - Sensor 1
MID: $4d TID: $91
Min: 55327 Max: 57, 344
Current: 65,523

High sensor Voltage for switch time calculation
MID: $d0 TID: $04
Min: 51247 Max: 57344
Current: 65523

And then a couple others with no descriptions:
MID: $ee TID: $0d (at 65,523)
MID: $1c TID: $56 (at 0)

I'm guessing the readings at 65K are essentially null values since they seem too close to 2^16 to be anything else.

I should also note there are non-zero amounts of misfires for various cylinders on the engine. The counts didn't surpassed whatever baked-in limits, but I have no idea to judge whether they're high or low. Are misfires even common on modern engines?

All help appreciated. Apologies if I'm presenting data in a useless newbie-like manner. It's my first time diving into OBD data on a Mustang. Happy to go back to Torque and pull whatever's relevant.
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post #6 of 33 (permalink) Old 02-04-2013
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Read this post and see if any of this might be happening.

https://www.allfordmustangs.com/forum...-question.html

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post #7 of 33 (permalink) Old 02-04-2013 Thread Starter
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Sounds exactly like my problem. Other than a bunch of chatter between Ford and various pissed-off owners, I didn't see any real solution other than updating the PCM, which maybe is it. Will try hunting down Ford service, I guess. Some of that guys on that thread were thinking of returning their cars. Hope it doesn't come to that.
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post #8 of 33 (permalink) Old 02-04-2013
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Before you get to excited,contact Deysha on this site, she is our Ford Customer service Rep explain your problem to her,then sit back and watch the magic happen,Deysha will get your problem resolved.
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post #9 of 33 (permalink) Old 02-04-2013 Thread Starter
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Thanks! Just PM'ed her on that other thread. I'm hoping she comes through. A bit at wit's end right now.
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I don't know if it helps you too entirely much but I watch mine out of curiosity all the time. Mine goes to 20:1 when there is no load and I am coasting in gear. I have no issues however, if I tap the throttle even the slightest, it drops back to normal.


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post #11 of 33 (permalink) Old 02-04-2013 Thread Starter
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Quote:
Originally Posted by Oyyci View Post
I don't know if it helps you too entirely much but I watch mine out of curiosity all the time. Mine goes to 20:1 when there is no load and I am coasting in gear. I have no issues however, if I tap the throttle even the slightest, it drops back to normal.
Thanks! When mine isn't freaking out and losing power, that's also true for me.

Good to hear the behavior is part of a general pattern.
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Looks like a misfire to me.... It will spike lean with each misfire since raw oxygen (and fuel) will be going into the exhaust. That'd explain the lack of power, blinking CEL, and misfire counts.

No misfire codes present at all? That's unusual given the fact that the CEL was blinking, unless it went away for awhile during driving. If it starts blinking again, pull the codes. I bet you'll see a misfire code setting. Which sensor is reading this? It'll help isolate it to a particular bank.

Going to 20% is normal during decel when coasting in gear since you'll be in a nonfueling state. Essentially, you are reading atmospheric oxygen content (20.8%) at that time. Many systems self calibrate during that driving state to establish a free air reference. However, if the OP was under load when this was occurring it is almost definitely a misfire.

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Before you get to excited,contact Deysha on this site, she is our Ford Customer service Rep explain your problem to her,then sit back and watch the magic happen,Deysha will get your problem resolved.
Thanks again, 5.0 Coyote! :p

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Thanks! Just PM'ed her on that other thread. I'm hoping she comes through. A bit at wit's end right now.
Thank you for the PM, anoniogm. Ill get back to you as soon as possible.

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Quote:
Originally Posted by 2011GrabberGT View Post
Looks like a misfire to me.... It will spike lean with each misfire since raw oxygen (and fuel) will be going into the exhaust. That'd explain the lack of power, blinking CEL, and misfire counts.

No misfire codes present at all? That's unusual given the fact that the CEL was blinking, unless it went away for awhile during driving. If it starts blinking again, pull the codes. I bet you'll see a misfire code setting. Which sensor is reading this? It'll help isolate it to a particular bank.

Going to 20% is normal during decel when coasting in gear since you'll be in a nonfueling state. Essentially, you are reading atmospheric oxygen content (20.8%) at that time. Many systems self calibrate during that driving state to establish a free air reference. However, if the OP was under load when this was occurring it is almost definitely a misfire.
Agreed. It's also possible that the fuel cut off (FCO) state that's present during decel is also commanded during a detected shift. I know the LS1 stuff from 10-15 years back had it. Can't imagine why it'd be a whole lot different these days...even across platforms. So, the AFR spikes might be normal and a separate issue from the misfires.

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I looked the other day at my afr gauge (premium) and I ran my car through the gears. It never seemed to drop lower than 13.8-14.1. Is this possibly because my car was built dec 17th supposedly after the pcm update?


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