Has anyone encountered this issue? (2016 Mustang GT/CS stalling while idle, purchased used)

magus21

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Video link (Reddit)

Basically, once the car is warmed up, every time I’d come to a stop and put the car in neutral (foot off clutch), there’s a 50-50 chance that the car would start to sputter/surge/etc. Sometimes I can catch it quick enough by jabbing the gas pedal, but if I just let it happen, then the car eventually stalls. A couple of times, it stalled on me as I was about to shift into gear to go uphill.

I’ve been dealing with this issue for about a year now since I got the car in Fall 2019. At first it was very minor and sporadic, but over time it got worse.

I took it to the dealer back in June 2020 when it got really bad. They said it was a dirty throttle body, so they cleaned it and let me go on my way. A couple of weeks later, it started acting up again.

I had separate battery-related issues that led to me changing the battery last week, and I had a faint hope that maybe the problem was due to the battery (e.g. electrical problems messing with sensors/pumps/injectors, etc.), but obviously it wasn’t.

At the same time as when I changed the battery, I also read that an oiled filter can sometimes foul the MAF, and I did put in a K&N drop-in filter back when I first got the car, so I swapped out the drop-in filter for a normal paper filter (still no dice), and yesterday, I cleaned the MAF with some MAF spray and drove it around for about an hour. But today, it’s still doing it.

There is no real pattern to it other than that it only happens at idle. Otherwise, the car runs GREAT when it’s on the move.

I have practically no mods on it, just these:

- SmartTOP module (automated convertible top)
- Borla S-Type catback exhaust
- K&N oiled drop-in filter (now removed)

Note: I’ve already received advice on Reddit (r/Mustang) that it’s probably the throttle body, so that’s probably my next replacement, but I’m looking for confirmations and second opinions for other possibilities in case it doesn’t turn out to be the case.

I also ordered an OBD reader so I should be able to capture codes once that arrives in a day or two.

I’ve seen other “rough idle/stalling” threads on this forum, but the RPM jumps and AF ratios of the videos posted to those threads don’t quite look the same. My engine seems to drop then surge rhythmically rather than sporadically, and the AF ratio doesn’t go high. I’ve seen it go to 15 at times, but most of the time the AF ratio drops/gets richer, whereas other people complain about AF ratios going super high/lean. Also, many of those other stalling incidents happen while driving, and that’s never happened to me. In fact, it runs nice and smooth while driving.
 

Elp_jc

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It could also be a cam phaser. When they go bad, that's exactly what happens, for what I've read. Not sure if they throw a code at that time, so you might want to search for that. I'd immediately hook up your car to FORScan, and see what it throws. Good luck.
 

lint28

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I had the same issue. I cleaned the MAF and the problem was solved! Its a cheap enough solution to at least try.
 

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