Surging throttle

[TW Merema]

Hello guys, I just bought a 2020 GT with a Borla Type S exhaust and no other engine mods that I know of. I have noticed the surging in the video occurs while steady state cruising, it doesn't really seem to matter what gear though it's noticeable most in 4th-6th at lower RPM's. Here is a video, I used the vacuum gauge to illustrate that there seems to be something weird going on with the throttle perhaps?



I also noticed the grill shutters moving a lot while it was idling the other day, and I have the code in the attached pic for the air shutter limit switches. I had it at the dealer today for the PCM recall, hoping the reprogramming would help but it doesn't seem to have. The tech there blamed the Borla (of course) and said it was causing air surges. I'll admit I am not a mechanic but I have an awful lot of experience with modified cars and never had that happen with a cat-back. Anyone else have this issue, if so what is the fix?

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[Zelek]

That has absolutely nothing to do with the catback. It could be a malfunctioning active grill shutter though. Something may have damaged the connector or it's unplugged.

 

[KingKona]

Take.

It.

In.

 

[TW Merema]

That has absolutely nothing to do with the catback. It could be a malfunctioning active grill shutter though. Something may have damaged the connector or it's unplugged.

I did check, the shutter seems to be plugged in and the plug is fine. Car only has 6,000 miles on it so unlikely that anything is broken or damaged but you never know.

 

[TW Merema]

Take.

It.

In.

As you read above, I took the car to the dealer and the tech blamed the catback. Most technicians are just parts changers these days and don't really understand how to diagnose, so I was hoping to have a direction to point them in when I do take it back in.

 

[Mspider]

As you read above, I took the car to the dealer and the tech blamed the catback. Most technicians are just parts changers these days and don't really understand how to diagnose, so I was hoping to have a direction to point them in when I do take it back in.

have you considered taking the car to a different dealership?

 

[TW Merema]

have you considered taking the car to a different dealership?

I have made an appointment at a different dealer, though I’m not hopeful. Took my F150 there last year for a recall and I had to provide the recall number since they couldn’t find it (had gotten a notice through FordPass). I just figured someone here might have had a similar issue and could share the outcome, which I plan to do once this is solved.

 

[KingKona]

Hello guys, I just bought a 2020 GT with a Borla Type S exhaust and no other engine mods that I know of.

If you bought a used Mustang with an after-market exhaust, then the dealership you bought it from should take care of all of this.

It will take some forceful bitching on your part, but they should handle it.

 

[TW Merema]

If you bought a used Mustang with an after-market exhaust, then the dealership you bought it from should take care of all of this.

It will take some forceful bitching on your part, but they should handle it.

Understand and appreciate that, but to the root of the issue why would a catback exhaust cause this problem on this particular Mustang when it seems none of the other 8 million Mustangs with catbacks have the issue?

 

[TW Merema]

Well, I got some more information on the issue I believe. Last night on the highway about 2000 rpm in 6th gear (cruise set) I got a CEL. Pulled the code and got a P0369 Cam Position Sensor B Circuit Intermittent (Bank 1). Both cam sensors seem to be plugged in properly and don't look suspect, but I'm going back to the dealer with new info. I'll update if I get an answer.

 

[KingKona]

Understand and appreciate that, but to the root of the issue why would a catback exhaust cause this problem on this particular Mustang when it seems none of the other 8 million Mustangs with catbacks have the issue?

The point behind my suggestion is that a cat-back shouldn't, and something else is causing the issue. Let the dealership diagnose it, let them figure out the issue.

Then let us know what it was.

 

[TW Merema]

The point behind my suggestion is that a cat-back shouldn't, and something else is causing the issue. Let the dealership diagnose it, let them figure out the issue.

Then let us know what it was.

That's my plan. I'm hoping between the resonator I ordered to put on (Borla Type S is a bit loud for my taste) and the additional code they'll at least look into it instead of giving me a BS answer.

 

[KingKona]

That's my plan. I'm hoping between the resonator I ordered to put on (Borla Type S is a bit loud for my taste) and the additional code they'll at least look into it instead of giving me a BS answer.

Take the car back to the dealer you bought it from, in the condition you bought it.

It's their responsibility to fix anything wrong.

 

[Schwerin]

Take.

It.

In.

Learn.

To.

Read.

 

[Conman1138]

Hello guys, I just bought a 2020 GT with a Borla Type S exhaust and no other engine mods that I know of. I have noticed the surging in the video occurs while steady state cruising, it doesn't really seem to matter what gear though it's noticeable most in 4th-6th at lower RPM's. Here is a video, I used the vacuum gauge to illustrate that there seems to be something weird going on with the throttle perhaps?



I also noticed the grill shutters moving a lot while it was idling the other day, and I have the code in the attached pic for the air shutter limit switches. I had it at the dealer today for the PCM recall, hoping the reprogramming would help but it doesn't seem to have. The tech there blamed the Borla (of course) and said it was causing air surges. I'll admit I am not a mechanic but I have an awful lot of experience with modified cars and never had that happen with a cat-back. Anyone else have this issue, if so what is the fix?

I experienced a somewhat similar issue when I bought my car (used @3k miles). The engine had a constant surging pattern at steady throttle, in any gear, cruise control on or off. My vacuum gauge showed further movement than yours, and I could actually hear the engine trying to load up in the exhaust note. It was like a 2-second cycle, load up and unload, constantly.

I never got any DTCs, however. My dealership replaced the electronic throttle body and intake cam phasers, neither of which fixed the problem. They eventually had a Ford engineer take a look, who approved an engine replacement, which solved the problem. I never got any word on what the cause of the problem was, if they ever found it.

I haven't had any problems in 30k miles since!

I hope in your case it's just a simple sensor or something. I haven't really seen anyone else with a similar problem to mine, I'll be following this thread for sure.

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