2013 FR-S…stalls…hard to restart
 

Hey all, trying to teach my son how to drive MT on 2013 FR-S. As you might expect, a bit rough on the car with a newbie used to a AT. He stalled it a number of times (trying to work clutch / gas). The problem that has developed though…the car has started to stall and restarts very hard. It seems as if I wait for 15 - 30 min it will start easier. It hadn’t thrown any ECU codes…with the exception of one today (P0335) (crank position sensor) after an extended period of trying to start it. I plan to replace the sensor, as it would explain my issues…but I wonder if it threw code due to weak battery. When it stalled today…started up prior and I drove it 5 minutes to gas station. I topped off the tank…car hesitated to start after fill up…but did. I went to pull out in road…car died and would not restart…eventually did…about 20 minutes later after sitting…although not a smooth start…this was the first time I had seen any ECU code (noted previously). Car is new to us (son’s car)…private sale…about 95000 miles…engine replaced recently with used from a 2013. When running, sounds good, runs strong. Prior to driving lessons…drove car 3 or 4 times…maybe 50 miles total…no issues. Hoping to find advice from others that may have dealt with similar issues.

welcome!

my first suspicion is bad gas.

do you have any indication of the mileage of the replacement motor? a major service interval is 60k for most all fluids and spark plugs. might be due for that maintenance as well.

my rule of thumb with used vehicles is "in a lack of proof of maintenance history, assume zero maintenance was performed"

Soundman98, thanks for the feedback. I wondered about gas…also if maybe it was the LPFP and / or filter (I’m assuming the pump has an internal filter/screen). I’m waiting on the crank sensor (not convinced it’s bad…but cheap and easy replacement). After that…will look at the fuel system a bit closer. It really seems to me fuel related. To answer your questions…replacement engine had about 90k…no maintenance records available…although I do know plugs were replaced during a engine swap, fluids changed, etc. Open to any and all recommendations / advice. Will update here as process unfolds.

yea, i would just take a long spirited drive to drain the tank most of the way to empty. fill up with a more name-brand place the next time, and if you're feeling generous, maybe throw some stabil in the tank as well.

Bet it is a bad battery.

Starting (or attempting to start) an engine is the hardest thing a battery does. The alternator takes 20-30 minutes of over 1,500RPM just to replace the voltage used during 1 start. That is why short trips with multiple starts are bad for batteries. If it is a battery that is 2-3 years old already, it compounds the problem. The stalling is caused by a faulty idle relearn due to low voltage after losing voltage.

No No No you don't check the battery first you start by putting a test light on the ignition circuit! (sic) Or so I am told. Over and over.

OK sarcasm aside this is exactly what it sounds like. The battery is weak enough that it doesn't have time to "rebuild" it's charge between starts.

this is the part that i noticed most.

if it was just hard to start, that might indicate to me just a bad battery. of course, it could be both as well...

Sorry lack of updates…just haven’t had time to work on. I did replace the crank position sensor, and made sure the battery was fully charged (battery is less than a year old) Drove it 15 min (about 8 miles) this am to my parents. Started and ran great. Car was off about 15 minutes…went to restart and it took 4-5 tries to get it to start. On the way out…noticed as I shifted into second gear quick hiccup(lost fuel or spark very briefly…and from there drove home fine until I reached hill near my house. I was headed down hill…going about 45/50 and it just died. I coasted into a vacant lot…waited 10 minutes is so…and car started on 2/3 try. Drove it home and parked in garage. No engine codes thrown during entire excursion.

sputtering while driving, and hard to start with a good battery would indicate to me either a fueling or spark issue.

spark plugs are supposed to be 60k miles. coil packs are suspicious-- many replace with spark plugs due to the difficulty of getting down there, but i believe they're considered 'lifetime'.

are you still on the same tank of gas from before?

My strategic approach has already been ridiculed once in this thread despite my absence, but here goes again.

Do you have any idea what the fuel trims are doing?

Same tank of fuel…haven’t had time to drive it…partly because I don’t trust it will stay running/restart…also because the weather is turning here in Maine and I want to avoid the road salt. I have no fuel mapping info…will have to look into coming up with. Whatever the issue…I’ve only noticed when the engine is warm…never has an issue starting it cold(at least thus far. A CEL would be helpful…but I don’t get any.

My guess is a clogged fuel filter.
Just a guess but I had the same symptoms on a cross country trip. Took me a couple thousand miles and many stops and stalls to figure it out. It usually stalled out going up hill.

Update…found today that there is a bad connection in the engine bay…AB1 / AC2 / AC1 plug connector location on the wiring diagram. At this point not sure exactly what the issue is…but definitely an issue. If I just slightly move the wire bundle with engine running…it will cut out…no associated CEL. I had ordered an LP fuel pump / filter…still plan to replace those…but I think primary issue is a bad/loose connection or wire. TBD.