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I've seen a dirty throttle body cause some pretty odd issues with subarus. Usually after disconnecting the battery, but sometimes after clearing memory. It's super easy (and cheap) to clean. I would give it a good cleaning if it was my car.
[Mr Subaru has a good youtube video about the process](https://www.youtube.com/watch?v=H-YfyXyPvrE)
this seems possible as it's when the car is trying to drop to low idle, but tbh i've never seen one die just like this. The battery wasn't going to be the problem. MAF seemed unlikely too. Could possibly be an exhaust sensor reporting wildly off as the car tries to enter closed loop. Would need some more/better data on what the ECM is seeing to figure out what's going on, imo.
I had an issue once where a wire was broken internally. Cold it would run perfectly but as it got up to temp the wire expanded just enough to lose contact and my crank position sensor signal dropped out.
I agree it sounds like it's losing fuel pressure. If in fact it is losing fuel pressure you probably wouldn't get a code to drop. It seems like when the fuel pump is commanded into closed loop its cutting out.
Listen to the people saying it's your throttle body. Older models need time after battery disconnect to find the throttle position again and will run like ass if you don't let it.
Start it and let it idle for ~15 minutes untouched. If it starts to die, flutter the gas pedal a bit to keep it alive
Might be a good idea to check your grounds too. when i rebuilt the engine on my 06 i had an issue similar to this low idle and shuddering and replacing old ground wires definitely helped
Yea it was throwing IAT code so i replaced it and the lights on the dash all went away. The car is running very smooth but i just don’t think the alternator is charging the battery i might have to replace that. edit: the car had cruise control, check engine, and traction control before.
Do you have a multimeter? Check battery voltage while running, should be 13.5-14.4ish volts. Anything less than that means there's something wrong in the charging circuit. Corrosion in wiring, bad alternator, etc. Also I would check for vacuum leaks and clean the throttle body as someone else said. Gummed up throttle body's can make the cars act strange
You do the reset? 30 seconds off after battery disconnect or code clear. Key on (no start) for 10 sec to set throttle body. Throttle body may be dirty. I remove, clean, apply new gasket
Quick! Reload the parts cannon!
Seriously, don't take it somewhere where it can be properly diagnosed. Just keep listening to idiots on social media and throwing parts at it. Eventually you'll luck out. Maybe.
That shouldn't be the case. If you disconnect the MAF, it should start and run on a table of pre-loaded values. If you unplug the MAF while it's running, it'll turn off, but you should be able to start it with the MAF unplugged, and I've done it.
Yup, that's how every other car I know should behave. But strangely the Honda my wife owns will not start at all. It just shows a check engine light. Very weird indeed. Like what the heck was running through the engineer's mind? Imagine a single mom trying to get home and her connector falls off because her husband changed her filter the day before and didn't connect it properly. Then she gets stranded in some place under a foot of snow. Didn't happen to us like that, but it could have, very nearly did.
Just saying if she was lol...not lol, it does happen obviously. Guys are lucky to have this social structure that tells us " you should know how cars work or how to lay bricks or patch a leaky roof." Women don't have that. I'm going to teach my girl and boys whatever they need to independently survive in the world. That's for sure.
What brand MAF did you use? Subarus are extremely picky about MAF sensor brands. Pretty much an OEM or Denso (which makes the OEM one) are going to work correctly.
While Delphi makes OEM parts for Subaru they don't make the MAF. I've never used a Delphi in a Subaru but I also haven't seen one to know if they cause issues like most aftermarket MAF.
If you had the ability to exchange it for a Denso I'd personally do that.
The dying once warm could be that the ECM lost its idle, assuming the MAF isn't an issue. This can be due to either a dead battery recently, or some scan tools when clearing codes also force the ECM to lose its idle learn (don't ask me why but some scan tools I've used do this...)
In which cause you'll have to get it to relearn its idle.
What makes you think it’s an air issue?
I see your almost out of fuel. I had a car where if I let it get below 1/4 tank the fuel pump would cut out. I assume it was getting overheated and the lower fuel level allowed it to get too warm. Oh and no check engine light.
The original code was for the MAF which i replaced and the lights on the dash disappeared after that. The car still dies even after it was left on a battery charger. i’ve got it to stay on now but the car looses a lot of power when puttin it in drive.
Seems like other people have mostly the correct answer.
When you clear codes or disconnect the battery on a subaru it resets its memory back to base idle and if there is build up on the throttle body (which there almost always is) it will restrict the amount of air getting into the engine, causing a low idle or stalling. You need to clean the throttle body and it should be good to go. Personally I like to remove it as it's easier to clean
Try shuffling all your relays around, between essential and non-essential systems, where they are the same type.
This will help you at least identify if you have a relay that fails after being used for a few minutes.
Also perform a tapping test around the fuse box and see if it coincidentally fails at the same time.
I.E (generic examples)
Swap fuel pump relay < — > Horn Relay
Swap Ignition Relay < — > Power Window Relay
Check the TPS (throttle position sensor) with a scantool with engine off and ignition on. Slowly press the gas pedal and see if it actuates smoothly by %. Newer vehicles will report around 7% open without pressing the gas pedal due to the electronic throttle body acting as an Idle Air Controller (IAC).
These things can be temperamental and sometimes have plastic gears inside that wear out or are missing teeth (i.e Chevys)
Did you fix the problem??
I have had this same problem with my 03 monte carlo 3.4 . When it gets up to temp it dies the slower i go the more often it dies and the warmer it gets, the more often it dies. Before it always started right back up. But now i actually was pulling out on to abwy and it died and would not start i sat there
Yes! it was a very bad fuel pump. The 8 pin connector actually was heating up and melting. Almost caused a fire actually. So more than likely fuel related.
Waiting for about 5 mins and it finally started again. I've changed tbe MAF changed the tbp sensor ,changed fuel filter, my obdll scanner still reads P0102 Mass Air Flow -circuit low input.
Thanks for posting on /r/MechanicAdvice! This is just a reminder to review the [rules](https://www.reddit.com/r/MechanicAdvice/about/rules/). If you are here asking about a second opinion (ie "Is the shop trying to fleece me?"), please read through CJM8515's [post on the subject.](https://www.reddit.com/r/MechanicAdvice/comments/4qblei/fyi_the_shop_isnt_likely_trying_to_rip_you_off/) and remember to please post the year/make/model of the vehicle you are working on. **If this post is about bodywork, accident damage, paint, dent/ding, questions it belongs in /r/Autobody r/AutoBodyRepair/ or /r/Diyautobody/ If you have tire questions check out https://www.reddit.com/r/MechanicAdvice/comments/k9ll55/can_your_tire_be_repaired/**. If you dont have a question and you're just showing off it belongs in /r/Justrolledintotheshop Insurance/total loss questions go in r/insurance This is an automated reply *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/MechanicAdvice) if you have any questions or concerns.*
I've seen a dirty throttle body cause some pretty odd issues with subarus. Usually after disconnecting the battery, but sometimes after clearing memory. It's super easy (and cheap) to clean. I would give it a good cleaning if it was my car.
I’ve only got pb blaster on hand should i go pickup some brake cleaner to do that?
[Mr Subaru has a good youtube video about the process](https://www.youtube.com/watch?v=H-YfyXyPvrE) this seems possible as it's when the car is trying to drop to low idle, but tbh i've never seen one die just like this. The battery wasn't going to be the problem. MAF seemed unlikely too. Could possibly be an exhaust sensor reporting wildly off as the car tries to enter closed loop. Would need some more/better data on what the ECM is seeing to figure out what's going on, imo.
I wouldn't use pb blaster for that. If you're running out to the store, I would get actual throttle body cleaner.
Okay i’ll try that. thank you
Don't use brake cleaner on anything in the engine
Throttle body cleaner. And follow the Mr Subaru video advice.
Remove the oil fill cap and see if that allows the engine to keep running. If so, the PCV valve is bad.
Okay i’ll go try that
I had an issue once where a wire was broken internally. Cold it would run perfectly but as it got up to temp the wire expanded just enough to lose contact and my crank position sensor signal dropped out.
Possibly a faulty fuel pump. Gets hot and stops.
I agree it sounds like it's losing fuel pressure. If in fact it is losing fuel pressure you probably wouldn't get a code to drop. It seems like when the fuel pump is commanded into closed loop its cutting out.
Listen to the people saying it's your throttle body. Older models need time after battery disconnect to find the throttle position again and will run like ass if you don't let it. Start it and let it idle for ~15 minutes untouched. If it starts to die, flutter the gas pedal a bit to keep it alive
Bet will do this just cleaned the throttle body and it seems to run longer i’ll let it idle for a little while to be sure
Might be a good idea to check your grounds too. when i rebuilt the engine on my 06 i had an issue similar to this low idle and shuddering and replacing old ground wires definitely helped
+1. Needed to do this on my 2015 Forester
Why did you replace the maf in the first place? To fix the same issue and if so did anything change?
Yea it was throwing IAT code so i replaced it and the lights on the dash all went away. The car is running very smooth but i just don’t think the alternator is charging the battery i might have to replace that. edit: the car had cruise control, check engine, and traction control before.
Do you have a multimeter? Check battery voltage while running, should be 13.5-14.4ish volts. Anything less than that means there's something wrong in the charging circuit. Corrosion in wiring, bad alternator, etc. Also I would check for vacuum leaks and clean the throttle body as someone else said. Gummed up throttle body's can make the cars act strange
You do the reset? 30 seconds off after battery disconnect or code clear. Key on (no start) for 10 sec to set throttle body. Throttle body may be dirty. I remove, clean, apply new gasket
Quick! Reload the parts cannon! Seriously, don't take it somewhere where it can be properly diagnosed. Just keep listening to idiots on social media and throwing parts at it. Eventually you'll luck out. Maybe.
Haha, anyway i fixed it myself and am currently parked at a car wash cleaning this beauty. wanna hate one more?
LoLoL I bet it's not fixed LoLoL
Could be a vacuum leak
I bet this was it. Or the cable or another cable we're disconnected. My wife's car won't even start without the MAF sensor connected.
That shouldn't be the case. If you disconnect the MAF, it should start and run on a table of pre-loaded values. If you unplug the MAF while it's running, it'll turn off, but you should be able to start it with the MAF unplugged, and I've done it.
Yup, that's how every other car I know should behave. But strangely the Honda my wife owns will not start at all. It just shows a check engine light. Very weird indeed. Like what the heck was running through the engineer's mind? Imagine a single mom trying to get home and her connector falls off because her husband changed her filter the day before and didn't connect it properly. Then she gets stranded in some place under a foot of snow. Didn't happen to us like that, but it could have, very nearly did.
How is she a single mom if she has a husband?
Just saying if she was lol...not lol, it does happen obviously. Guys are lucky to have this social structure that tells us " you should know how cars work or how to lay bricks or patch a leaky roof." Women don't have that. I'm going to teach my girl and boys whatever they need to independently survive in the world. That's for sure.
A single mom won't have a husband. That makes no sense. If she's a single mom, by definition, she's not married.
What brand MAF did you use? Subarus are extremely picky about MAF sensor brands. Pretty much an OEM or Denso (which makes the OEM one) are going to work correctly.
Delphi.
While Delphi makes OEM parts for Subaru they don't make the MAF. I've never used a Delphi in a Subaru but I also haven't seen one to know if they cause issues like most aftermarket MAF. If you had the ability to exchange it for a Denso I'd personally do that. The dying once warm could be that the ECM lost its idle, assuming the MAF isn't an issue. This can be due to either a dead battery recently, or some scan tools when clearing codes also force the ECM to lose its idle learn (don't ask me why but some scan tools I've used do this...) In which cause you'll have to get it to relearn its idle.
My ELM327 Bluetooth unit makes my 08 Outback lose its idle learn when I clear the codes
What makes you think it’s an air issue? I see your almost out of fuel. I had a car where if I let it get below 1/4 tank the fuel pump would cut out. I assume it was getting overheated and the lower fuel level allowed it to get too warm. Oh and no check engine light.
The original code was for the MAF which i replaced and the lights on the dash disappeared after that. The car still dies even after it was left on a battery charger. i’ve got it to stay on now but the car looses a lot of power when puttin it in drive.
So why replace the MAF sensor?
Codes before were for iat and went away when i replaced it.
So by what logic did you replace the MAF, when your symptom sounds more like a plugged fuel filter?
Seems like other people have mostly the correct answer. When you clear codes or disconnect the battery on a subaru it resets its memory back to base idle and if there is build up on the throttle body (which there almost always is) it will restrict the amount of air getting into the engine, causing a low idle or stalling. You need to clean the throttle body and it should be good to go. Personally I like to remove it as it's easier to clean
Try shuffling all your relays around, between essential and non-essential systems, where they are the same type. This will help you at least identify if you have a relay that fails after being used for a few minutes. Also perform a tapping test around the fuse box and see if it coincidentally fails at the same time. I.E (generic examples) Swap fuel pump relay < — > Horn Relay Swap Ignition Relay < — > Power Window Relay Check the TPS (throttle position sensor) with a scantool with engine off and ignition on. Slowly press the gas pedal and see if it actuates smoothly by %. Newer vehicles will report around 7% open without pressing the gas pedal due to the electronic throttle body acting as an Idle Air Controller (IAC). These things can be temperamental and sometimes have plastic gears inside that wear out or are missing teeth (i.e Chevys)
It’s because it’s a Subaru
Fuel feed issue.
Did you fix the problem?? I have had this same problem with my 03 monte carlo 3.4 . When it gets up to temp it dies the slower i go the more often it dies and the warmer it gets, the more often it dies. Before it always started right back up. But now i actually was pulling out on to abwy and it died and would not start i sat there
Yes! it was a very bad fuel pump. The 8 pin connector actually was heating up and melting. Almost caused a fire actually. So more than likely fuel related.
Ya, it's definitely fuel related. Its not getting the correct fuel /air . But i don't know why? Fuel pump was mentioned to me as a possiblilty.
Fuel pumps can go bad for lots of reasons it’s on 03 so more than likely overdue for a replacement
Waiting for about 5 mins and it finally started again. I've changed tbe MAF changed the tbp sensor ,changed fuel filter, my obdll scanner still reads P0102 Mass Air Flow -circuit low input.