Random Stumble/Stall Issue

I just picked this car up yesterday and plan on bringing it back to the dealer for this issue, but I'd still like some background information just to make sure they aren't blowing smoke up my a$$.

 

Issue: Randomly the car stumbles & stalls when coming to a stop; stumbles at an idle. No CEL lights, do plan on checking for codes before I bring it to the dealer.

 

Car: 2006 Legacy GT 5AT

 

Back story: Dealer performed rebuild on the motor at 182,682. Current mileage is 184,xxx. New oil pump & water pump installed by the dealer.

 

I have all the paperwork from the dealer, so if somebody wants to take a look at what was done (some of the parts are only part #'s and I haven't had the chance to look them all up) just let me know and I can email them to you. Tried uploading them, but get the token error and really can't resize a PDF.

 

Thanks in advance for any help!

Make sure there's no vacuum/boost leaks, clean the MAF sensor, reset the ECU and drive the car around for a couple days (or just let it idle for a while). Mine still occasionally stumbles when coming to a stop, but it's rare. It's common after an ECU reset for these cars to stumble/stall when coming to a stop, but normally that will go away after the ECU learns it's low-airflow fuel trims.

Make sure there's no vacuum/boost leaks, clean the MAF sensor, reset the ECU and drive the car around for a couple days (or just let it idle for a while). Mine still occasionally stumbles when coming to a stop, but it's rare. It's common after an ECU reset for these cars to stumble/stall when coming to a stop, but normally that will go away after the ECU learns it's low-airflow fuel trims.

 

Thanks! I went digging through the pile of receipts and they changed the MAF sensor right before I picked it up, so I'll give it a few days.

You should invest in a logging tool such as the btssm app. It is hard to carefully diagnose issues without knowing what the ECU is really trying to do.

 

See here: http://www.btssm.com/

http://legacygt.com/forums/showthread.php/btssm-bluetooth-adapter-app-v-1-closed-229709.html

Plus 1 on logging data.

 

Plus 1 on intake/vacuum leaks. Logging data will help sort leaks out.

You should invest in a logging tool such as the btssm app. It is hard to carefully diagnose issues without knowing what the ECU is really trying to do.

 

See here: http://www.btssm.com/

http://legacygt.com/forums/showthread.php/btssm-bluetooth-adapter-app-v-1-closed-229709.html

 

I have been researching the blue tooth readers for a few days now, just trying to figure out which one I want to go with.

OBDLink MX FTW

I just ordered this one:

 

https://www.amazon.com/gp/product/B01HXGX8V6/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

 

I am going to get a Cobb setup shortly so this should hold me over till then.

mmh. I am not sure if this one will work. Are you planning to use the btssm app or something else with that dongle? Did you check that page?

http://www.btssm.com/?page=hardware

mmh. I am not sure if this one will work. Are you planning to use the btssm app or something else with that dongle? Did you check that page?

http://www.btssm.com/?page=hardware

 

I'm going to use Torque, which is recommended by the manufacturer of the dongle.

Problem is torque will not report the critical variables you want to log for a Subaru ECU. The Btssm app is far superior in that respect.

Critical variables I am referring to are feedback knock correction, fine learning knock correction, misfire per cylinder, long term fuel trims, fuel correction, etc...

 

I also have torque btw.

Point noted...downloaded Btssm. I'll have the dongle tomorrow and can return it if it does not work with the app.

 

Thank you for the help. This is a whole new world for me. I'm use to old school V-8...couple vac lines, maybe 2 or 3 sensors and that completed the computer system. LOL

I'll be very interested to see if that dongle will work with BtSsm; please post the results. If it works, it will provide full diagnosis capability to casual DIYers for under $25. Maybe we'll see fewer people trying to replace diagnosis with the parts cannon.

Anyone wanna lay odds? I'd give it 1 in 5 chance of working.

My buddy has a 2013 WRX and uses it on his car with no connection issues, though I am not sure what app he uses. But he is the one who recommended the one I purchased. But I'll be sure to report my findings.

The key is to be able to read the critical data via what they call the "K-line". I understand that some dongles apparently can't read on that 'line'. The developer of this app (heiche on this forum) can probably tell you right away if this dongle will work.

It has already shipped and I'll have it tomorrow. If it don't work then I'll just return it and grab one from his site then.

The key is to be able to read the critical data via what they call the "K-line". I understand that some dongles apparently can't read on that 'line'. The developer of this app (heiche on this forum) can probably tell you right away if this dongle will work.

 

You were right the dongle doesn't work with the app.

 

But, I did trip a CEL light this morning and while in there pulled a pending code.

 

Pending code: "P0420 - Catalyst System; Bank 1: Efficiency Below Threshold"

Active code: "P0244 - Turbocharger Wastegate Solenoid A Range/Performance"

 

I'm going to have the dealer change out the downstream O2 sensor to check on the P0420 code.

 

I'm thinking the P0244 is a tune issue for the following reasons (feel free if you think I am on the wrong track)

 

1) Mechanic at dealership said he replaced the turbo with the "more powerful of the 2 options" -- he couldn't tell me much else and I can't find a receipt for whatever he put in.

 

2) Idle is around 500 in Park and drops to around 300 in D

 

3) Wastegate dumped at 4500 RPMS -- no where near redline

 

4) Fuel mileage is HORRIBLE (like 12-13 MPG combined)

 

I am going to check vacuum lines during my lunch break. I'm going to a tuner shop Saturday that only deals with Subarus (theSUBARUshop in Tiverton, RI) to talk to him about all this.

 

Do plan on putting on new up and down pipes and exhaust within 2 months, so kinda hoping I can hold off on the tune until then if I am not going to do any damage.

 

1 question: My timing is advancing 30 deg+ at times. Is that normal on the 2.5?

Any mods on the car? None of this sounds reasonable for a perfectly stock car, and if that's the case, I don't see how you'd have a tune problem (assuming the tune is also OEM).

 

P0244 is overboost, if I remember correctly. If you hit that during a pull, it'll feel like you drove into a wall. If by "wastegate dumped at 4500 RPMs" you mean that's when you got the code, that makes sense, as that's about where you might see peak boost (as it tapers away towards redline).

 

If it was a dealership, I don't see why they wouldn't use the stock turbo, so "more powerful of the 2 options" doesn't really make much sense. Unless he meant VF46 (from the '07-'09MY) instead of the VF40 ('05-'06).

 

The idle is way too low, stock tune calls for 700-800RPM.

 

The ignition timing sounds about right. I'm not sure about the '05-'06, but stock cruise timing for the '07+ is around 40°.

 

If your car isn't knocking (you'll need to use BtSsm to check, and also learn a bit about Subaru's knock control methodology), then you probably aren't doing any damage to the engine.

Yeah. I'd say step 0 is to get the right cable/dongle to have btssm running so you can log the 'good stuff' .

 

In the meantime, do check that you do not have any vacuum leak anywhere.

Also, do you have a stock air filter?

solidxsnake - Subaru dealer did the engine rebuild, dealer I bought from was a small "Mom&Pop" shop and the mechanic was a younger guy, so I believe he thought he was doing a good thing. I am going to try and get the model off the turbo today.

 

I have zero clue if it has the OEM tune or not.

 

No mods on the car.

 

I'm getting the right dongle for BtSsm next week, already have the app.

 

xt2005bonbon - Stock filter box with stock filter (that is listed on the receipt from the Subaru dealership.)

 

As usual, appreciate the assistance. Trying to get up to speed on these cars while having an issue is proving to be frustrating. I'm use to old school American V-8 running on OBD-1.

OK. Then while you wait, you can read the first post of this thread. You may learn a thing or two.

 

http://legacygt.com/forums/showthread.php/checking-general-health-your-engine-and-tune-210369.html

You have to hold the brake pedal for 20 seconds to reset the ECU?

I no longer do that since btssm can do that. But I think torque can do that as well when you ask to clear the codes. But in general, I do not reset my ECU. I try to address an issue, and then observe how the ECU behaves right after the fix.

Ok. So it's not actually "resetting" the ECU like you would reset a cell phone, just "Clearing the Codes" as I'm used to having it referred to.

I believe clearing the codes does indeed reset the ECU. Resetting the ECU would do the following for instance,

--the ECU may have learned over time to pull some timing at a certain load/rpm condition. Well, when you reset the ECU (using whatever method prescribed), the ECU will no longer pull timing there.

--the ECU may have learned to add, say, 5% of fuel at idle due to a small vacuum leak somewhere. Resetting the ECU will erase that info.