Air/fuel ratio spiking in a new Mustang, sometimes losing power. - Page 2 - Ford Mustang Forum
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Originally Posted by JeffCO. Coyote View Post
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?
Under heavy throttle, it should drop into the 12's. if it didn't, you were probably not on the gas hard enough.


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Quote:
Originally Posted by JeffCO. Coyote View Post
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?
Believe it or not this is normal. If you do a search for my past posts you will see that I already went through this paranoia. The best explanation so far came from [email protected] I'm not going to go through reciting what Shawn have posted through numerous posts on svtp forum but surprisingly this seem to be a norm so far. It doesn't seem to affect all 2013 mustangs either because some guys see exactly what I thought I should see which is low 12's on wot. I already went through my dealer regarding stoich on wot and they said everything is all within spec and nothing to worry about. However, just to note, ford racing pro cal and my current diablo all have brought my AFR to what I'm used to, which is low 12's on wot.


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Quote:
Originally Posted by antoniogm View Post
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.

There are two possibilities here. One is that it is misfiring due to something like a bad coil or plug and as a result of this major fault the ECM is commanding the injectors (and spark) to cut resulting in the lean spikes you see. The other possibility is that the A/F is going lean due to either an ECM or mechanical (fuel system) issue and that is causing the misfires (lean A/F mix does combust properly and will result in a misfire)
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Quote:
Originally Posted by JeffCO. Coyote View Post
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?
Mine drops to the commanded 0.82 PE lambda (~12.0-12.2 A/F) on my 2013 at WOT. I am self tuned though.
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A misfire in and of itself will also cause a lean spike in the exhaust, rich, lean, compression, or spark induced.

I don't think this is from shifting either, otherwise this guy is a hell of a lot faster than humanly possible given how rapid some of these spikes are. Not enough gears for the amount of spiking either.

Need more data to confirm if it is under load the entire time or not.....

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post #21 of 33 (permalink) Old 02-05-2013 Thread Starter
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Originally Posted by 2011GrabberGT View Post
A misfire in and of itself will also cause a lean spike in the exhaust, rich, lean, compression, or spark induced.

I don't think this is from shifting either, otherwise this guy is a hell of a lot faster than humanly possible given how rapid some of these spikes are. Not enough gears for the amount of spiking either.

Need more data to confirm if it is under load the entire time or not.....
What other data do you need? Would an RPM time series help?

Not sure if Torque lets me log/show two separate time series.
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RPM, TPS (or APS), Engine Load...... It's almost definitely a misfire regardless of all of that, based on everything else you're experiencing. What bank sensor are you reading off of? That'll be the suspect bank and narrow it down a bit.

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post #23 of 33 (permalink) Old 02-06-2013 Thread Starter
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This TSB seems very relevant:

http://www.fordservicecontent.com/pu...sb13-01-11.pdf

In fact, seems to describe it exactly.
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post #24 of 33 (permalink) Old 02-08-2013 Thread Starter
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So I took it to the dealer with a pile of misfire codes on it. They claim to have followed the TSB and reflashed the PCM to something more recent.

The car comes back seeming a lot less performant, and with less lower-range torque. The engine, over a day of driving, gradually wakes up. Nothing happens for maybe 50 miles.

But then...it starts happening again. CEL on, engine misfiring and losing power, Torque Pro firing error codes on three cylinders.

At this point, not sure what to do. Would flashing some custom tune maybe fix it, since it seems like a purely software problem?
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Quote:
Originally Posted by antoniogm View Post
So I took it to the dealer with a pile of misfire codes on it. They claim to have followed the TSB and reflashed the PCM to something more recent.

The car comes back seeming a lot less performant, and with less lower-range torque. The engine, over a day of driving, gradually wakes up. Nothing happens for maybe 50 miles.

But then...it starts happening again. CEL on, engine misfiring and losing power, Torque Pro firing error codes on three cylinders.

At this point, not sure what to do. Would flashing some custom tune maybe fix it, since it seems like a purely software problem?

A tune is merely tweaks to parameters within the existing software and that will not fix your problem. When getting a PCM flash at the dealership they are actually re-writing the base software of the control unit and is far more involved.

Basically you need to go back and have them continue with the diagnosis to find the cause of your issue. Make sure Deysha is in the loop.
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That TSB specifies no driveability problems.

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post #27 of 33 (permalink) Old 02-08-2013 Thread Starter
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That TSB specifies no driveability problems.
That's an excellent point. They applied the patch anyhow. I guess it's not surprising it didn't clear it.

About to head out on a 5-hour car trip. Hope the car makes it.

Which raises the question: can recurring episodes of misfires cause permanent damage to the engine?
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Long term or continous misfire can cause damage. If your CEL is still blinking I would advise against a long road trip. The best thing to do is to let your dealer take care of the issue until it's solved completely.

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post #29 of 33 (permalink) Old 02-08-2013 Thread Starter
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Quote:
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Long term or continous misfire can cause damage. If your CEL is still blinking I would advise against a long road trip. The best thing to do is to let your dealer take care of the issue until it's solved completely.
To be clear, it doesn't blink 24/7. I take it out on the highway, and it will have an episode, more like an epileptic seizure, and then resolve. And if I keep the revs low and shifting calm, and it doesn't come back.

Driving it around the city, doesn't happen.

Still a bad idea?
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If it's an ignition induced misfire and you are dumping raw fuel down the exhaust, the cats are not going to last very long.


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