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.
