Running lean after hitting the rev limiter

[axios]

Hi everyone, I’ve been experiencing some weirdness with my Mustang GT after hitting the rev limiter last week.

Immediately after that the fuel got cut off and the car lost power for a brief second. After the power came back, the engine immediately felt a bit weird.

I took the car in for service but they couldn’t find any problems with it. It definitely feels different so I was wondering if anyone had any idea about how to diagnose the issue.

Here are the symptoms:
- It feels like it’s running lean as it’s not developing the same power as it used to and it doesn’t respond well to throttle at low RPMs
- Both the engine and exhaust sound different, not as deep as before
- It feels flat around 3k RPM
- No check engine light
- No OBD error codes

Any help would be appreciated.

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[Dalas]

I can't say it for sure, but I have the same feeling, I don't think mine is running flat around any RPM but the exhaust note has changed and power seems to be less.

 

[Zinc03svt]

What year mustang??

 

[5.oh]

you aren't really going to be able to tell that the car is running lean by what your butt dyno tells you. Pull the spark plugs or check the AFR

 

[Dalas]

Mine is 2017.

 

[Joe 5.0]

From what I've read, bouncing off of the rev limiter isn't horrendous if it happens infrequently. The rev limiter is in place so we don't do serious damage to the engine, and the limit is set way below what the engine could actually handle.

I highly doubt damage was done from pegging the rev limiter one time. If you're really concerned, monitor your AFR. If your car is on pump gas, I believe the AFR should be around ~14.0.

 

[Dalas]

Yeah, I think this would do no harm if it is sporadic. I think maybe the spark plug but I haven't had the time, nor the knowledge to check. I just bought the car and still learning to navigate my way around it.

 

[Joe 5.0]

Yeah, I think this would do no harm if it is sporadic. I think maybe the spark plug but I haven't had the time, nor the knowledge to check. I just bought the car and still learning to navigate my way around it.

Watch this video. This is the exact process.

 

[axios]

Mine is 2015 with perf pack, 10k miles. I already checked the AFR and it was hovering around 14 in idle. It did look a bit weird while driving, like it wasn’t steady at constant speed.

 

[Joe 5.0]

Mine is 2015 with perf pack, 10k miles. I already checked the AFR and it was hovering around 14 in idle. It did look a bit weird while driving, like it wasn’t steady at constant speed.

AFR will fluctuate while you're driving. That's normal. It will also shoot up to 20.0 sometimes when you're off of the throttle and just coasting.

If and when you fill up with E85 (with the proper tune), your AFR will sit around 9.8.

 

[choate]

i guess on i'm one tonight but this stuff is so basic with performance cars it cracks me up. OP you are just getting used to your power. you don't need to pull the plugs unless it's misfiring b/c they are supposed to last 100k miles.

 

[choate]

check the AFR at WOT for at least 5 secs WOT to see if it's "leaning out". you're reading too many "Termi" Forums man! AFR is a FI thing. you're getting plenty of fuel i assure you. unless something in the fuel system failed

 

[thehunterooo]

check the AFR at WOT for at least 5 secs WOT to see if it's "leaning out". you're reading too many "Termi" Forums man! AFR is a FI thing. you're getting plenty of fuel i assure you. unless something in the fuel system failed

M6G is the fourm of paranoia. My car made a weird sound? Time to demand Ford to buy it back or lemon law it!!!

 

[axios]

Ok, problem fixed - life is great again.

Went to pick up my car this morning and as soon as I started it up I knew things were good. They did the 10k mile service on it before even looking into the engine issue - after that they couldn’t reproduce the problem any more. I chatted with the technican about what they did and he said that their standard procedure is to upgrade the software and also reset the throttle position sensor. I am pretty sure the sensor was behind it.

 

[Joe 5.0]

Ok, problem fixed - life is great again.

Went to pick up my car this morning and as soon as I started it up I knew things were good. They did the 10k mile service on it before even looking into the engine issue - after that they couldn’t reproduce the problem any more. I chatted with the technican about what they did and he said that their standard procedure is to upgrade the software and also reset the throttle position sensor. I am pretty sure the sensor was behind it.

Glad to hear that! Enjoy your car and don't worry about the little things (just try your best to avoid the rev limiter, haha).

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