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05-13-2019, 06:15 PM | #1 |
Scooby Newbie
Member#: 373996
Join Date: Nov 2013
Chapter/Region:
South East
Location: clearwater fl
Vehicle:2015 FXT Touring Quartz Blue Pearl |
2015 FXT rough idle stalling at stop
I just purchased a CPO FXT touring about a month ago from a local dealer. About a week after my purchase I twice got Code P0172 while driving. I took it to the dealer and they said they couldn't find anything wrong, updated the ECM and blamed the CEL on my insurance's OBD2 plug in. Today after driving home when stopped I got a rough/low idle and the car would stall, No CEL, and started right back up. Any ideas of what could be the cause? Car is stock.
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05-13-2019, 09:39 PM | #2 | |
Scooby Newbie
Member#: 473534
Join Date: Aug 2017
Location: Kansas City, MO
Vehicle:15 WRX Prem. w/ HK CWP |
Quote:
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05-13-2019, 11:08 PM | #3 |
Scooby Newbie
Member#: 373996
Join Date: Nov 2013
Chapter/Region:
South East
Location: clearwater fl
Vehicle:2015 FXT Touring Quartz Blue Pearl |
73k miles I sprayed the MAF and the code hasn't returned after. Its been multiple tanks of gas. This is my first turbo car, so I don't know how to tell if i have a boost leak or not. I would think 02 sensor would throw a code, which is why I'm at a loss and seeing if this was a common issue with the FXT or the WRX.
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05-13-2019, 11:29 PM | #4 | |
Scooby Newbie
Member#: 473534
Join Date: Aug 2017
Location: Kansas City, MO
Vehicle:15 WRX Prem. w/ HK CWP |
Quote:
Also, low or erratic idle can be caused by the oil control valves (part of the active timing system). I had to change one out due to a hunting/rough idle. Failures of that component are common enough. Hard to diagnose though, unless you can see the avcs angles. Dealer will diagnose by moving the valves around. I watched mine on an accessport. $45 later it was fixed. |
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05-14-2019, 07:18 AM | #5 |
Scooby Newbie
Member#: 373996
Join Date: Nov 2013
Chapter/Region:
South East
Location: clearwater fl
Vehicle:2015 FXT Touring Quartz Blue Pearl |
Update: Code P0172 came back this morning along with a rough idle.
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05-14-2019, 09:41 AM | #6 |
Scooby Newbie
Member#: 452248
Join Date: Aug 2016
Chapter/Region:
MWSOC
Location: Cleveland Ohio
Vehicle:2017 Base WRX WRB |
check the clamps on the charge pipe to inter cooler, and inter cooler to throttle body. I believe there was an issue with them coming loose on the early forester FA20DIT models.
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05-14-2019, 09:47 AM | #7 |
Scooby Specialist
Member#: 337626
Join Date: Nov 2012
Chapter/Region:
TXIC
Location: Dallas, Texas
Vehicle:2015 WRX Crystal White Pearl |
check the battery terminals, mine were loose and the same thing happened
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05-14-2019, 11:54 AM | #8 |
Scooby Newbie
Member#: 373996
Join Date: Nov 2013
Chapter/Region:
South East
Location: clearwater fl
Vehicle:2015 FXT Touring Quartz Blue Pearl |
Just got back from dealer they replaced MAF and O2 sensor lets see if that fixes it.
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05-16-2019, 01:45 PM | #9 |
Scooby Specialist
Member#: 83725
Join Date: Mar 2005
Chapter/Region:
NESIC
Vehicle:2015 WRX |
If the issue comes back you may want to check out this thread.
I had the rough idle and stall occurring on my WRX and after following that thread and replacing the part my issue went away. |
05-17-2019, 01:05 PM | #10 |
Scooby Newbie
Member#: 310796
Join Date: Feb 2012
Location: UT
Vehicle:05 obxt |
OP, you should get some kind of software to view your live short term and long term fuel trims. It is hard to guess without knowing what the ECU reports. It sounds to me that your have some boost leak somewhere (that is if you are running rich and MAF/o2 sensors are good). If you are running lean, then it is a vaccum leak.
Not super familiar with your engine design, but there should be a way to find such leaks. As for the ECU params, I use the Btssm app (see here). Been using this for over 5 years now. Has helped me countless of time. As a matter of fact, helped me troubleshoot poor MAF connection a couple of days ago. |
05-19-2019, 08:02 PM | #11 |
Scooby Newbie
Member#: 312223
Join Date: Mar 2012
Chapter/Region:
RMIC
Location: Colorado Springs
Vehicle:2002 WRX Silver |
We've done a bunch of bulk head harnesses to fix this concern.
I had one you could watch the short term fuel trim go to -21%, then I could grab the main harness by the VDC unit, wiggle it and it'd jump to +7 instantly. |
05-20-2019, 12:39 AM | #12 |
Scooby Newbie
Member#: 310796
Join Date: Feb 2012
Location: UT
Vehicle:05 obxt |
^Yes!
Very similar issue I had on my 06 (OBXT): last week, let the car idle, fuel trim around -6% (which I don't like), opened hood, bent MAF wires close to MAF while watching fuel corrections, and bam fuel trim slowly making it back to 0%.... Very sensitive system. Now mine is a 15 years old wiring harness while yours (OP) is much newer. So, YMMV. |
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