Topic: Stalling issues on 2008 Impreza

[klatch]

I have a 2008 Impreza and am having some issues. The car will run fine, though sometimes it is a bit hesitant to start, but will intermittently get a rough tremble to it, like it wants to stall, and then the light that illuminates when you intentionally disable traction control will flash, but it doesn't stall, until today. Today I was driving 80km/h and the vehicle stalled instantly - without a tremble or hesitation, illuminating the battery light, the oil light, the check engine light and the traction control off light. I pulled over and started back up again no problem, drove for about a minute and it stalled out again, same thing, and I started it up again without issue. I made it to my destination, then had another short trip to a friends house without issue. He hooked up his obdii tool and it didn't show any errors in the system. When I was leaving his house I started up my car and a moment after it did the rough tremble and flashed the disable traction control light, perhaps almost stalling, but was fine and I drove all the way home without issue. Any thoughts? I need to resolve this. I see in the impreza section there is an STI that seems to have a similar issue. http://www.westernsubaruclub.com/smf/index.php?topic=53400.0 In that thread there is some thought it is a fuel issue - potentially same thing here?

I replaced my battery the other day, but had the rough sputtering before then. Sometimes my vehicle seems harder to start then it should be.

I'm going to need a shop to look at it and do whatever needs to be done, but want to have an idea of where to ask them to look.

[thedude]

This sounds very familiar to an issue my dad's Tundra had back in the day. After countless times bringing it to the shop and trying to explain the situation (since it wouldn't repeat on demand) the situation got worse and worse. Eventually they were able to find out that there was loose/frayed wiring which caused the truck to suddenly stall.

I'm not sure if it is comparable but by the sounds of your problem, electrical shouldn't be ruled out. I'm sure some of the other guys will chime in as well but with no codes showing, its pretty hard to determine what the cause might be.

[klatch]

Eventually they were able to find out that there was loose/frayed wiring which caused the truck to suddenly stall.

Sigh, I was hoping there would be a clear direction, but more information is good. Do you know what wiring was frayed/loose?

[ultimatt]

Is your battery good?

[Jay89]

Is your battery good?

Seems he replaced it recently but happens before and after battery replacement

[klatch]

Seems he replaced it recently but happens before and after battery replacement

Exactly. Brand new AGM but was having issues before, though seems to be getting worse as I hadn't had the stalls like yesterday before - though my wife says she had one a few years ago.

[ultimatt]

Auto or manual?

Doesn't have an aftermarket remote start does it?

[klatch]

Auto or manual?

Doesn't have an aftermarket remote start does it?

Manual. And yes, it has an aftermarket remote start that was installed by Powersource Performance in Edmonton. Good question - I meant to mention it.

[ButterBear]

Im not the most knowledgeable about the operation of a car under the hood, but one time I was driving my car failed to accelerated and just felt very heavy and slow. The cause of that was the fuel pump not working properly, but when I googled the symptoms I believe it also mentioned spark plugs, and or dirty intake filter/+maf sensor. If it has a wacky idle and stalls thats a common sign of a vacuum leak.

I repeat im not the most knowledgeable but hopefully it helps 

[klatch]

Thanks for your thoughts - fuel issue makes sense to me as well. I've got it in to a shop and hopefully they can figure it out. I'll be sure to post back what they do, and whether it fixed it - though with the intermittent nature it may take a while to know.

Edit. I spoke with the shop yesterday and so far the vehicle hasn't displayed the problem for them, so they haven't tried to fix anything. Hopefully it shows itself today when they take it on a few road tests.

Edit 2: They still couldn't get anything to happen for them, so I'll have to see if it happens and wait for the issue to become worse I suppose.

[k-dani29]

It might get expensive but see if the shop has a OBD2 flight recorder they can install. then drive your car and when the stalling begins you push the button on the flight recorder and it will catch freeze frame data and tell you what your long term and short term fuel trims are doing as well as sensors they have selected. that when they can at least have something to go on.

[Polaris]

Dang, sounds similar to what my car had/sort of still has. It would stutter/shake/RPMs would drop super low and threaten to stall out unless I gave it gas or mashed the brakes, usually happened at super low speeds when I'm off-load cruising up to a red light, or through a playground zone, or into a parking stall, but also happened more often reversing up a hill. No codes, and can't for the life of me reproduce it when it's at a shop haha, never been able to get it to shake/stall when I'm at the shop, but happens to me when I'm alone

Might be transmission fluid? I topped mine up with new fluid and it happens super rarely now, hoping to get a full flush sometime soon and see if it works. Others have also suggested O2 sensor, fuel pump, or torque converter, if the transmission fluid change doesn't fix mine I might try to change the O2 sensor.

[klatch]

Dang, sounds similar to what my car had/sort of still has. It would stutter/shake/RPMs would drop super low and threaten to stall out unless I gave it gas or mashed the brakes, usually happened at super low speeds when I'm off-load cruising up to a red light, or through a playground zone, or into a parking stall, but also happened more often reversing up a hill. No codes, and can't for the life of me reproduce it when it's at a shop haha, never been able to get it to shake/stall when I'm at the shop, but happens to me when I'm alone

Might be transmission fluid? I topped mine up with new fluid and it happens super rarely now, hoping to get a full flush sometime soon and see if it works. Others have also suggested O2 sensor, fuel pump, or torque converter, if the transmission fluid change doesn't fix mine I might try to change the O2 sensor.

Interesting that you have had similar things. I've also noticed that the shuddering happens generally (exclusively?) at slow speeds, I've called it mainly a parking lot issue.  Does your traction disable light flash when this happens? I had Apex Specialialized change the transmission fluid when they did my timing belt and a bunch of other work a bit over a year ago - so I'm going to guess it isn't that - unless they didn't actually do it (also had them do a teraclean injector cleaner/decarbonization). Doesn't explain two stalls when going 80km/h within a few minutes of each other. Is the O2 sensor easy to change? Is it something that needs to be done at some point anyways? I had the spark plugs done about a year and a half ago, maybe they aren't quite good enough spark plugs? Sigh.. This thing is so frustrating. Car has been perfect last few days. I can't remember when this started maybe after spark plugs replaced?Could it be a spark plug issue? Thoughts?

[lophilip]

On 2006 Impreza the drive by wire throttle body needed to be calibrated if the battery was removed. I believe the 2008 Impreza do not require this, but you can try that.

Also a faulty throttle body sensor, or a dirty throttle body will cause that issue as well.

All drive by wire subarus are susceptible and sensitive dirty throttle bodies, so I would start by cleaning that.

[Jay89]

Try cleaning your maf. Pick up some cheap crappy tire maf cleaner spray. Might help.

[klatch]

Try cleaning your maf. Pick up some cheap crappy tire maf cleaner spray. Might help.

Just identify and then spray the wires from what google is telling me, correct? I'm seeing a few things suggest resetting the ECU, which I don't know if is needed and don't know how to do, though perhaps a google search can tell me how, though I'd prefer someone here telling me if I should. I'm handy, but my forte isn't automotive.

I haven't actually had any issues since the ones that prompted this post, but fully expect them to return.

On 2006 Impreza the drive by wire throttle body needed to be calibrated if the battery was removed. I believe the 2008 Impreza do not require this, but you can try that.

Also a faulty throttle body sensor, or a dirty throttle body will cause that issue as well.

All drive by wire subarus are susceptible and sensitive dirty throttle bodies, so I would start by cleaning that.

I'll look in to this also, especially when it warms up (I don't have a heated garage).

[bejamin]

I have a 2009 forester that had very similar issues that started after disconnecting the battery one time (resetting the ECU). Turns out that the throttle body was gunked up around the butterfly valve. So when the car shuts the valve to idle there wasn't sufficient air passing due to the gunk. This caused all sorts of issues, random surges, stalls and hard starts. It couldn't calibrate itself.
It took 10 minutes and some brake cleaner and it's been purring like a kitten since. I make a point of cleaning throttle body's as part of a yearly Maintenance schedule or any engine swap/replacement projects.
Hope this is your issue. Otherwise it's time to start digging.

[Polaris]

When cleaning the throttle body, do you wipe it with a shop towel for example, or is it like the MAF where you just spray it and forget about it (let it dry)? My TB was cleaned this past summer but it didn't seem like a lot of gunk was on there, like after spraying it and letting it sit a bit the resulting "fluid" didn't look too brown or dirty to me, wasn't sure if maybe we needed to wipe the plate itself.

[klatch]

I have a 2009 forester that had very similar issues that started after disconnecting the battery one time (resetting the ECU). Turns out that the throttle body was gunked up around the butterfly valve. So when the car shuts the valve to idle there wasn't sufficient air passing due to the gunk. This caused all sorts of issues, random surges, stalls and hard starts. It couldn't calibrate itself.
It took 10 minutes and some brake cleaner and it's been purring like a kitten since. I make a point of cleaning throttle body's as part of a yearly Maintenance schedule or any engine swap/replacement projects.
Hope this is your issue. Otherwise it's time to start digging.

Yeah, a dirty throttle body sounds like the probable issue. I'm just trying to get a clear answer on how to safely clean it since I am under the impression it is drive by wire, and I don't want to mess things up. It isn't clear if I can move the valve at all or not, or only if the battery is disconnected or what. Anyone have some insight on what to do/not do? Would be appreciated.

Does disconnecting the battery reset the ECU? That would explain why things were worse after the new battery. Edit: From what I read, it seems that a long disconnect (though unsure how long) will reset the ECU. This would explain the stalling issues etc after replacing the battery.

Edit: I'm going to not touch the valve but lay something on the accelerator (vehicle off, but keys in "on" position) and open the valve to clean it that way. Then make sure the battery is disconnected for a while to reset the ECU. I'm hoping I can get at all the parts easily enough and that this resolves the issues, though they haven't really arisen since the ECU has relearned whatever it needed to learn (assuming that is the difference).

[bejamin]

To do a good job of cleaning the valve, take all the electrical connectors and hoses off (clamp the coolant hoses) and unbolt it (4 bolts). Take it completely off. You can manually move the valve just don't force it to move too fast (you'll feel resistance, let it move slowely). Use brake cleaner, a rag and even que tips to get in the nook and cranny's.
I have brought a new throttle body to intake mani gasket before but after that I realized that as long as you're careful with the existing gasket you will be fine on reinstallation. Be sure to use the correct torque when reinstalling the 4 bolts.
My ecu had learned to deal with the issue too but I found that fuel economy was suffering and it smelt like I was running super rich at times which scares me because unburnt fuel is not much fun for your catalytic converters. Plus everytime i pulled the battery to work on the car it went back to its old habits for awhile until the ecu learnt its lesson again.
Let us know if this fixes the issue.

[klatch]

I cleaned the MAF and left battery disconnected overnight (resetting ECU) and had same sort of issues after, so MAF cleaning doesn't seem to have fixed anything, or at least not everything.

Managed to work up the courage to take things apart to get to the throttle body. This is the before picture for the throttle body (can anyone comment if this is clean/normal/dirty for a 2008?):


I wasn't wanting/willing to take it off. I did use broom on the gas petal to open up the valve, but tried not to put too much pressure on at any point as I didn't want to move it or screw things up. I got it as clean as I reasonably could:


I then disconnected the battery for about 4 hours and took it for a ride. It didn't start on the first crank (same thing happened after cleaning MAF and having the battery disconnected) but I took it for a drive and didn't have any issues. It seems to be better and to have resolved the issue as I haven't been able to drive that far without having an issue right after having the ECU reset, assuming that 4 hours is long enough to reset the ECU. So I'm going to optimistically think this is good/resolved, but I will monitor and post back. Definitely doesn't seem to have hurt anything. Seems not to be idling as rough and not sounding "harsher" when I do things like turn on A/C or the rear defrost. Thanks for your help all.

[klatch]

It has been a few weeks and it seems cleaning the throttle body resolved the issue. As it turns out, a friend was having rough idle issues with his Mazda 3 and cleaning the throttle body and MAF sensor fixed him right up too. Thanks all.

[bejamin]

Thanks for posting back with the results, good to hear it's all back to normal!

[cheech00TS]

I've got a 2011 Impreza that has had some hesitation, rough idle, and poor fuel economy (especially in the city) so I'm thinking of trying the same things as you. Did you take the MAF sensor off or just spray it while it was on the car? Most of the info I've read says that you're better off removing it, but just looking for a bit of insight from someone local who's done it. Thanks for posting your issues. Its nice to see a fellow NA driver every once in a while.

[klatch]

I've got a 2011 Impreza that has had some hesitation, rough idle, and poor fuel economy (especially in the city) so I'm thinking of trying the same things as you. Did you take the MAF sensor off or just spray it while it was on the car? Most of the info I've read says that you're better off removing it, but just looking for a bit of insight from someone local who's done it. Thanks for posting your issues. Its nice to see a fellow NA driver every once in a while.

I took the MAF sensor off - not sure how you would spray it without taking it off. It is two screws to take out and disconnecting the electrical wiring to it. Cleaning the MAF sensor is super easy and takes all of about 3 minutes, if you stop for a 1 or 2 minute break. The throttle body was the part that I didn't take off, though I'm sure pros would have done so. I just did as good of a job as I could without taking it off and was really careful not to move it manually and things seem fine now. Make sense? Good luck.