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2017 Stalls/dies intermittently

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#1
I have no CEL and my Cobb accessport shows no codes.

couple weeks ago, my throttle body went bad and i replaced it and everything was fine until this week

several times now, it has stalled out while moving, once at a pretty high rate of speed on the highway.

it seems like it happens when i let off the throttle or put it in neutral and coast, i havent had it happen when under acceleration.

i have no other symptoms. when its not about to stall out, it idles nice and smooth. i have no loss of power, accessport shows no weird timing or ignition offsets, and im 99.9% certain i installed the throttle body correctly because im still at 25psi boost and a solid vaccuum when off the throttle, which i imagine would be lessened if air was leaking in around the throttle body or something. and if it wasnt plugged all the way in, it wouldnt work at all.

its not good to have my car just shut off on me and its even worse at 75mph on the interstate.

any ideas would be appreciated.


EDITED SEPTEMBER 4 2021:

pcv valve and evap harness keep reading for details, i made a huge post at the end explaining my whole story, all symptoms, how it happened, how i diagnosed it and i share with you what NOT to do.
 


Last edited:
OP
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Thread Starter #3
25psi on what turbo? I know the EVAP harness can cause issues and it's short money to replace. What year and how many miles?
45k miles and its a 2017

25psi on stock turbo, which is rated for 21 with overboost.

ive heard about the evap harness but nobody else was saying their car died while moving, it was always a story about how it dies when sitting at idle for a few seconds

and i dont have any codes, other people were saying the evap harness throws a code p0443 or something
 


OP
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Thread Starter #5
quick update, I've now got p2196 o2 sensor stuck rich, which confirms my stalling issue

im assuming either my 02 sensor has gone bad or maybe an injector is stuck open or a spark plug has gone out

I'll replace the sensor and check my spark plugs for burn marks tomorrow

edit: i also put a new air filter in yesterday, and noticed it was way thicker than the old one. its there any way at all it could be smothering the engine or am i insane for thinking that
 


TyphoonFiST

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#6
quick update, I've now got p2196 o2 sensor stuck rich, which confirms my stalling issue

im assuming either my 02 sensor has gone bad or maybe an injector is stuck open or a spark plug has gone out

I'll replace the sensor and check my spark plugs for burn marks tomorrow

edit: i also put a new air filter in yesterday, and noticed it was way thicker than the old one. its there any way at all it could be smothering the engine or am i insane for thinking that
Get an oil analysis done by Blackstone Laboratories every oil change ....this will set you free and let you know if there is and how much fuel is in the oil* cheap insurance and let's you know what's in your oil!

Sent from my SM-N975U1 using Tapatalk
 


Last edited:
OP
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Thread Starter #7
Get an oil analysis done by Blackstone Laboratories ever oil change ....this will se you free and let you know if there is and how much fuel is in the oil* cheap insurance and let's you know what's in your oil!

Sent from my SM-N975U1 using Tapatalk

lmao, thanks Blackstone shill! good advice
 


OP
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Thread Starter #8
Just an update:

ive double and triple checked all the hoses and electrical connections and i dont think anything is unplugged so i shouldnt be leaking vacuum or anything.

Im guessing its either

A: i installed my new throttle body wrong.

B: the O2 sensor has simply gone bad.

its gotta be one or the other because those are the only two things ive messed with recently other than the slew of hoses and wires i had to move around to get to them.

Does anyone know if theres a gasket on the manifold where the throttle body mounts? the new throttle body didnt come with a gasket and the old one didnt have a gasket on it, so theres either no gasket or the gasket is on the manifold itself and not the throttle body.
 


OP
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Thread Starter #9
Another update:

i have tested and confirmed that the following is working properly:

both o2 sensors (upstream and downstream)

MAF sensor

throttle body (i mentioned earlier it went bad and i just replaced it)

Im still running rich. the p2196 code says o2 sensor signal biased/stuck rich
 


OP
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Thread Starter #11
i figured it out.

It turns out the CABLE to my mass air flow sensor was bad.

the place where it connected to the rest of the wiring up underneath my battery box had somehow got all chewed up by something. rats, heat, i have no idea.

but the insulation was gone and the bare wires were touching, shorting out the signal to the MAF sensor.

and since it was only throwing the code when it shorted, my multimeter was showing the proper voltage across the MAF itself

replaced the MAF just in case the shorting damaged it, and ran new wires.

runs like brand new, totally fixed and no issues since.
 


OP
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Thread Starter #18
Problem came back this morning on my way to work.

i have three codes now
p0131 (O2 low voltage bank 1 sensor 1)

p1450 (unable to bleed up fuel tank vacuum)

and

p2282 (Air leak between throttle body and intake valve)

Im assuming the o2 code and the air leak code are caused by the same problem, since an air leak somewhere could absolutely throw an o2 sensor code

only trouble is, when test driving it, i get -12psi vacuum and up to 24psi boost. if there was an air or vacuum leak, wouldnt those numbers be lower?

it idles much smoother now than it did before i swapped the MAF sensor, but it will spontaneously die and i cant seem to recreate the problem reliably enough.

it will die when coasting in neutral, but only sometimes. it will die at a stop light, but only sometimes.

it starts really rough as well, stumbles immediately after starting the engine and then smooths out after a few seconds and seems to run fine until it decides to spontaneously die again.

i have noticed a significant loss of power though. not nearly as much acceleration as im used to either. which could be explained by a vacuum/air leak, obviously.

anyone have any ideas on how to find an air leak? i tried the old school "spray carb cleaner at hoses and listen for rpms to go up" trick, but if its a leak that only happens sometimes, its not gonna do anything.

it almost seems like maybe a vacuum hose is sealing and unsealing itself. it will run smooth as you like for miles and then just die.
 


OP
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Thread Starter #19
ive got a theory, im gonna follow up this post in a few days and tell you all what i did.

i dont wanna keep typing out my "possible" fixes until i find the true problem and correct it.

that way if someone stumbles upon this post in the future and has a similar problem, they wont get a bunch of false information.

im moderately confident in my theory though
 


OP
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Thread Starter #20
Alright ladies and gents, I've got the definitive answer to all my problems, ive been driving for about three weeks now with not a single code (besides the torque limit code we all get with our fancy tunes)

So let me recap for those of you just now joining the conversation:

I drive a 2017 with a shit ton of aftermarket bolt ons because I'm a child in a man's body and i wanna be like Tokyo Drift.

1. A long time ago in 2019 i started getting intermittent stalling after a fill up. Would shudder at idle, and occasionally stall at stop lights here and there for like an hour after filling up at the gas station.

I googled it, looked around the forums, everybody said "yeah youll have to fix it eventually but its a known issue with the evap system, blah blah, replace the purge valve or the charcoal canister, you know the drill, it's code p1459.

Most of you are probably already familiar with that problem, everybody agreed it sucks but it's not a huge deal, so I put it on the "to-do" list and never got around to it.

2. Somewhere in mid June, it was 110 degrees Fahrenheit outside, and my throttle body seized wide open on the interstate while i was driving at about Mach 5 showing off for the cute girl in the stanced Miata in the lane next to me.

Engine revved to 20 million rpms, overheated, tried to go to limp mode but couldnt because the throttle body was just sucking air, scared the hell out of me and died, and i had to pull over.

Boiled the coolant, blew one of the nipples right off the radiator, it was a whole mess.

so i fixed all that stuff, new throttle body, got me a fancy throttle spacer from Boomba while i was at it because im gonna fix something, im gonna also get something fun while im at it because again, im 13 years old masquerading as 30.

3. This is where the problems really started. At this point i had fixed all the stuff that broke during my overheating near-death experience, BUT i was expecting to find other things going wrong because overheating your car until the radiator erupts is bad for it.

So i was disappointed, but not shocked when my car started stalling EVERYWHERE. just constantly. every time i let off the throttle, there was a SOLID 1/3 chance the car would die immediately.

doesnt matter if im at a dead stop, coasting, or braking, if I wasn't touching the accelerator, theres a 33.3% the car would stall and die in the next ten seconds.

at idle, it would chug like its flooding itself as it stalled, so i had some ideas but i wanted to wait for some codes.

Accessport was showing wild fluctuations from -4.00 to +4.00 ignition correction, hundreds of misfires in a 10 minute drive, and i was missing about 100 hp. i was basically driving a 115hp ST.

i could smell gas at idle, i could smell gas on the dipstick.

If it was extra hot out, it would stall a lot more than in the evening when it was cooler.

it stalled A LOT more WHEN FACING DOWNHILL. (ill get back to that)

After a couple days of this, it started throwing codes.

Here are the codes for your perusal, education and study:

P2282: Air leak between throttle body and intake (i know what you're thinking, you're thinking its the new throttle body spacer i got. but you're WRONG, just stick with me here)

P1459: fuel tank is unable to bleed up fuel tank vacuum.

p0121: O2 sensor low voltage, bank 1, sensor 1

P2196: O2 Sensor Signal Biased/Stuck Rich (Bank 1, Sensor 1

Okay, so when you get O2 sensor codes, whats the first thing you suspect after your engine overheated to hell?

thats right! you suspect that your exhaust reached the surface temperature of the sun and baked your O2 sensor into an aluminum quiche.

So i replaced the 02 sensor, cleared the codes and it didnt fix it.

So i thought hmmm lets take a look at that air leak code. Air leak between throttle body and intake, maybe i installed that spacer wrong or ruined the gasket, its sucking air, overcompensating with the fuel mixture and flooding itself.

so i took it all apart, replaced the gasket and buttoned it all back up.

Nope, wasnt that.

So now im thinking okay what else could mess up my intake air readings, cause a rich condition, and gets worse when its hot outside?

MAF SENSOR! oh hey and guess what? i cleaned all the gunk out of my airbox and replaced my airfilter a few weeks ago, maybe i got debris in the sensor or knocked it around too much.

so i cleaned the maf and it didnt help, so i REPLACED the maf and

nope, not fixed.

so i ran a compression test, maybe when it overheated, i seized a valve just enough that it wont open all the way now, so im running rich because im not getting enough air.

Compression test results were flawless. results were exactly at Ford OEM specs.

so i replaced all the spark plugs, thinking maybe an incomplete/bad spark is causing excess fuel to dump into the exhaust, setting off the O2 sensor.

nope, not fixed. but i did get some nice NGK iridiums spark plugs for free from a very nice guy i met at a car meet a few months prior. He had the sickest ST ive ever seen and really good hair.

Okay so i need to brainstorm.

What causes:

stalling
flooding
gas on dipstick
running rich
leak somewhere between the throttle body and the intake valves
gets worse when hot
gets way worse facing downhill
gas on dipstick

Well theres only one other connector between the throttle body and the intake and thats a little vacuum line that runs to the.....

pcv valve

the valve that leads from AFTER the throttle body, all the way back to the canister, and then to the fuel tank.

this valve is responsible for two things.

1. it vents excess pressure from the crankcase back into the intake

2. it allows excess fuel vapor collected from the gas tank (technically from the evap cannister) to get sucked into the engine for some environmental purpose blah blah emissions

If this valve wont open, excess crankcase pressure forces air and fuel down through the piston rings into the oil, engine doesnt get enough air at the right mixture and stalls. (its called a vapor lock if you ever need to google it) and my dipstick smells like gas.

when it wont close, it allows way too much fuel vapor to get sucked from the gas tank, causing rich condition. Also since its open when its not supposed to be, it also introduces a way for air to escape after the throttle body, causing an "air leak between throttle body and intake"

so the evap cannister valve went bad back in 2019 and started stalling after fill up, AND my pcv could have went bad when i overheated the car.

so fuel vapor is just completely unregulated between the cannister and the engine because both valves are bad. made worse by facing downhill as more fuel can collect at the front of the canister and run more easily into the intake. made worse when hot outside because more fuel vapor pressure is created from the thermal expansion of the system. running rich because too much fuel is getting in the car. stalling because it's vapor locked.


so if you get p1459, just pay the $300 to replace your EVAP canister and valve, and your pcv valve.

don't be like me and ignore it for two years until its a huge problem and then spend 3 months misdiagnosing your car all because some forum post told you the emissions related codes are no biggie.
 


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