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'17 Roush goes into "limp-mode"...help!

Old 06-24-2018, 07:09 PM
  #1  
RoushAnnie
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Join Date: Jun 2018
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Default '17 Roush goes into "limp-mode"...help!

Hi guys! Newbie here, bought a new Roushcharged GT back in Feb of '17. During the first 500 miles, I noticed a "hesitation" under light to moderate acceleration through all gears and at all speeds (yes, I'm old-school, so my performance cars are babied for the first 2k miles!) so no data under hard acceleration. Hesitation sound was ridiculously amplified by dealer-installed MBRP Race H-pipe exhaust; yep, nothing quite as embarrassing as slowly cruising through the subdivision in a shiny new hiccuping RoushStang! Anyway, I immediately took the car back to Joe Myers Ford in Houston, described the symptoms, and left it. Service writer called on 4th day and advised me to come get the car, that there were no codes thrown, that the tech drove it many times and "could not replicate symptoms", even flat-out stated "there's nothing wrong with it, they ALL run like that"...that was over a year ago and this IS my first new Mustang, so I convinced myself to 'just get used to it". I swapped the stupid-loud MBRP setup for a much more sedate pair of Borla mufflers and also added a high-end sound system so that I wouldn't be forced to listen to those tiny but annoying "nonexistent" hiccups...arrgh...

Fast forward many months and 2650miles to last Monday when the car stalled on gentle take-off at a 4way stop (it was raining buckets that day, lots of traffic ahead & behind). Pushed in clutch, pushed starter button, started fine & pulled away in 1st, went to 2nd (again, this was under gentle acceleration due to road conditions/poor visibility) car bucked & stumbled twice, heard loud exhaust "pop" followed immediately by yellow wrench light and limp mode. I had never seen the wrench light nor felt limp mode but had heard of both so I promptly pulled off the road, shut car off and waited for wrecker. Since warranty only covers 35mi haul and Joe Myers is nearly 90mi away, I had wrecker take us home so I could haul her there myself next week. On a side note, I did notice about a month ago that the engine would rev to nearly 2500 on cold start-up (had always stayed under 2k during warm-up before) then eventually settle back to idle. Other gauges all read normal, but A/F did bounce between 12.5 to 15, where before needle only bounced between 13.5-14.5 at idle and at steady speed, but car also seemed to run just a touch rougher. No idiot lights, no nothing, so I drove her normally, even stuck my foot in her a few times (ran like a scalded dog!), no issues. Then came that fateful day. I had my regular mechanic who routinely works on my other performance cars come to the house & run his scan tool on it; NO engine/drivetrain codes thrown, no indication of limp-mode activation, no nothing. He suspects possible throttle-body issue or one of many common sensors that should have at least thrown a code! Im in desperate need of advice here, guys, before I haul it down to dealer, again to be told "its all in my head"...then again, I am female, so thats a huge strike against me when dealing with any stealerships...I know just enough to get into trouble, and thats about it..


Thanks in advance...
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Old 06-25-2018, 02:00 PM
  #2  
Derf00
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Originally Posted by RoushAnnie View Post
Hi guys! Newbie here, bought a new Roushcharged GT back in Feb of '17. During the first 500 miles, I noticed a "hesitation" under light to moderate acceleration through all gears and at all speeds (yes, I'm old-school, so my performance cars are babied for the first 2k miles!) so no data under hard acceleration. Hesitation sound was ridiculously amplified by dealer-installed MBRP Race H-pipe exhaust; yep, nothing quite as embarrassing as slowly cruising through the subdivision in a shiny new hiccuping RoushStang! Anyway, I immediately took the car back to Joe Myers Ford in Houston, described the symptoms, and left it. Service writer called on 4th day and advised me to come get the car, that there were no codes thrown, that the tech drove it many times and "could not replicate symptoms", even flat-out stated "there's nothing wrong with it, they ALL run like that"...that was over a year ago and this IS my first new Mustang, so I convinced myself to 'just get used to it". I swapped the stupid-loud MBRP setup for a much more sedate pair of Borla mufflers and also added a high-end sound system so that I wouldn't be forced to listen to those tiny but annoying "nonexistent" hiccups...arrgh...

Fast forward many months and 2650miles to last Monday when the car stalled on gentle take-off at a 4way stop (it was raining buckets that day, lots of traffic ahead & behind). Pushed in clutch, pushed starter button, started fine & pulled away in 1st, went to 2nd (again, this was under gentle acceleration due to road conditions/poor visibility) car bucked & stumbled twice, heard loud exhaust "pop" followed immediately by yellow wrench light and limp mode. I had never seen the wrench light nor felt limp mode but had heard of both so I promptly pulled off the road, shut car off and waited for wrecker. Since warranty only covers 35mi haul and Joe Myers is nearly 90mi away, I had wrecker take us home so I could haul her there myself next week. On a side note, I did notice about a month ago that the engine would rev to nearly 2500 on cold start-up (had always stayed under 2k during warm-up before) then eventually settle back to idle. Other gauges all read normal, but A/F did bounce between 12.5 to 15, where before needle only bounced between 13.5-14.5 at idle and at steady speed, but car also seemed to run just a touch rougher. No idiot lights, no nothing, so I drove her normally, even stuck my foot in her a few times (ran like a scalded dog!), no issues. Then came that fateful day. I had my regular mechanic who routinely works on my other performance cars come to the house & run his scan tool on it; NO engine/drivetrain codes thrown, no indication of limp-mode activation, no nothing. He suspects possible throttle-body issue or one of many common sensors that should have at least thrown a code! Im in desperate need of advice here, guys, before I haul it down to dealer, again to be told "its all in my head"...then again, I am female, so thats a huge strike against me when dealing with any stealerships...I know just enough to get into trouble, and thats about it..


Thanks in advance...
I'd start with that. Sounds like a tune issue. Most FI cars are super sensitive to changes on the intake or exhaust side and the bouncing AF makes me think it's trying to correct for what it's seeing in the exhaust. Race H = no Cats or moved O2 sensors? No codes just means it's at the hairy edge which is why it acts up enough to be know but not to trip any sensors.
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Old 06-26-2018, 10:14 AM
  #3  
RoushAnnie
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Originally Posted by Derf00 View Post
I'd start with that. Sounds like a tune issue. Most FI cars are super sensitive to changes on the intake or exhaust side and the bouncing AF makes me think it's trying to correct for what it's seeing in the exhaust. Race H = no Cats or moved O2 sensors? No codes just means it's at the hairy edge which is why it acts up enough to be know but not to trip any sensors.
Thanks for the response!
MBRP “Race” vs “Street”, cat-back “H” vs “X” pipes; had exhaust guy lop off those mufflers & replace with Borlas...sorry for the confusion. When dealer first installed the MBRP setup (car only had 6mi on odometer), I asked if it needed a reflash, they said no, but I always wondered if that could have contributed to the annoying intermittent hesitation issue...and, of course, JMyers service told me that same thing when I took it in that first time...sigh...
Do you know if Roush modifies the TB or uses stock?I’ve heard that Roush is notorious for denying warranty claims (and painfully SLOW to respond to anything). I’m envisioning that car gathering dust in a service bay while we wait...ugh
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Old 06-27-2018, 02:50 PM
  #4  
Derf00
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If the Race H is a cat back system them it's not likely related to that since the O2 sensors and cats are intact in their stock locations.

However, this is what you have?
https://www.roushperformance.com/veh...shcharged.html

From the looks of it they keep the stock TB but you'd need to ask to be certain. Older Roush mustangs got upgraded to a Ford Racing type TB to handle the higher CFM required but I don't know much about stock component limitations on the newer stangs.

https://www.roushperformance.com/med...ers_Manual.pdf


Contact roush and take the car to authorized roush service center. The problem is most likely related to the tune, regardless of the h-pipe in this case. Just because a dealer sold it to you does not mean they are a roush authorized service center.
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