Ford Mustang Forum - View Single Post - Air/fuel ratio spiking in a new Mustang, sometimes losing power.
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post #18 of (permalink) Old 02-05-2013
Terminator2's Avatar
Joined: Nov 2012
Location: Lecanto
Posts: 96
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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