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Mystery stalling when braking ??


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42 replies to this topic

#1 SubeeTed

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Posted 15 October 2011 - 10:55 AM

Hi ALL!
I just got this '01 GT Wgn. I totaled my beloved '97 GT WGn, and got this. It's an automatic. It has 154 K miles on it. Runs fine except this weird problem. I've had the car now for about three weeks, it's happened to me 3 times. It just stalls when braking for a light or stop sign! It isn't heavy breaking, or emergency braking...can't figure it out! It runs and starts fine. Any ideas ??
HELP ! SubeeTed

#2 porcupine73

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Posted 15 October 2011 - 11:55 AM

Are you sure the brake booster is in good shape? I wonder if it were faulty if maybe a vacuum leak when braking would cause that?

#3 987687

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Posted 15 October 2011 - 12:01 PM

Do you have any check engine light codes, or a flashing AT temp light?
A faulty speed censor (or wiring) can cause weird stalling like this. Sounds weird, but I've had it happen.
You should get a check engine light with this, though.

#4 Red92

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Posted 15 October 2011 - 12:13 PM

My brother had a car once where the alternator was dying. The battery would get low enough that when you hit the brakes, the electrical load from the tail lights dropped the voltage enough that the engine would quit. I'm not sure what electrical part quit first- fuel pump, ECU, ignition... but it would run and drive great, just die at lights or when you were slowing down.

In his case, this also made it harder to start though. So if yours starts right back up fine, it is probably something else...

#5 SubeeTed

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Posted 15 October 2011 - 12:15 PM

I don't have a CEL on, no AT temp flashing.
Not shure about the booster or vac leak, have to check!
Thanks, SubeeTed

#6 Meeky Moose

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Posted 15 October 2011 - 01:15 PM

if the booster is bad you can reproduce the problem witting still..

put the car in gear, and mash on the brake pedal, if car dies then you have a booster with a vacuum leak. you may have to do it more than once or twice if its an intermittent problem..

#7 john40iowa

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Posted 15 October 2011 - 01:35 PM

You might just try some plug wires. My friend's 2000 Outback did the same
thing and this was all it needed to correct the problem.

#8 nipper

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Posted 15 October 2011 - 01:36 PM

First thing first, start with a tuneup.

#9 Highway_Star

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Posted 16 October 2011 - 03:47 PM

If the torque converter lock is on for some reason when you brake, it will make the engine stall just like a manual transmission with the clutch engaged.

#10 nipper

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Posted 16 October 2011 - 06:57 PM

If the torque converter lock is on for some reason when you brake, it will make the engine stall just like a manual transmission with the clutch engaged.


That rarely if ever happens anymore. i am going with the PB booster. :)

#11 davebugs

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Posted 16 October 2011 - 07:08 PM

I have someone with this problem on a 98 Outback.

Said they have had it several places and the last mechanic put it on the "computer" and said it's the trans. Hasn't stalled yet, but almost.

I have never had a real problem with a Subaru trans (torque bind and bearing noise on a few manuals aside).

So I believe they are taking it to my tranny guy.

If we learn anything I'll post here.

#12 KaraK

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Posted 18 October 2011 - 12:40 AM

Don't know a whole lot about my Soob (only had it a year) but... had two GM's do the same thing... was a selenoid in the tranny. ($25 part) that controls lock-up

#13 nipper

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Posted 18 October 2011 - 12:46 AM

Don't know a whole lot about my Soob (only had it a year) but... had two GM's do the same thing... was a selenoid in the tranny. ($25 part) that controls lock-up


Different control system on a subaru.

#14 SubeeTed

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Posted 27 November 2011 - 12:55 PM

Hi ALL!
Installed reman brake booster...NOT the problem! Still stalls, but less. I have the Auto Trans going into forward problem also, just added Trans X yesterday, hoped that MAYBE this would help with the stalling under hard braking, but NO! It did help the tranny though!
Is there a engine management sensor? Not the TPS, but one that also sits next to it, it manages throttle on the way down ?
HELP!!! SubeeTed

#15 davebugs

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Posted 27 November 2011 - 01:07 PM

The folks I know of who were having this issue - their fluid was low which didn't make ANY sense.

No leak marks, it was fine when I serviced the tranny before they bought it over a year ago - but it had been very overfilled. Like I drove it home 30 miles and it was well over a quart high. I drained the ATF, started with 4 new quarts and ended up with the usual - what 4.5 qts? Monitored it closely incase PO had a tranny issue - or caused one from overfilling. Tranny shop told me it took 4 qts!! But he couldn't find any signs of leakage.

If I hear any further news I'll update.

#16 SubeeTed

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Posted 27 November 2011 - 06:29 PM

Hi ALL!
OK...it's the Idle Air Controller (IAC) that I was thinking about ! Can it make the car stall under hard braking ? The car starts and idles fine! Can the IAC be checked ? Would it cause this hard braking stall ? I can stop it from stalling simply by letting my foot off the brake, this doesn't happen all the time, once off the brake, I just get back into it, it stops it from stalling. I have replaced the brake booster, it helped, the problem didn't go away!
Many thanks, HELP, SubeeTed !!

#17 nipper

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Posted 27 November 2011 - 07:09 PM

Yes the IAC controller can cause this to happen if sticking or dirty

#18 davebugs

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Posted 27 November 2011 - 07:12 PM

Im trying to get stuff on Ebay tonight and I have 2 IAC's pulled as some of the items to list.

One off a 97 2.5 one off a 96 2.2 but htey should be the same.

PM if interested. These engines ran is all I know. I started them before removing the engines.

#19 SubeeTed

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Posted 28 November 2011 - 08:10 AM

Hi ALL !
Thanks for the info !
I need to know how to clean the AIC, I found this procedure over at the NA Impreza site. I have a 2.5 SOHC in my 2001 Legacy. Is this the same AIC in this car ? Or were can I find the correct procedure for my car ?
Many thanks, SubeeTed

http://forums.nasioc...ad.php?t=781242

#20 porcupine73

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Posted 28 November 2011 - 08:36 AM

On the 2.5L phase II, the IAC is at the top of the throttle body, likely because it does not use a MAF. So to clean it you basically remove the air filter and housing, and then with the engine idling, spritz top end cleaner into the intake kind of aimed at the top. The engine will sputter each time, which is good because it probably makes the IACV open and close a bit to help with the cleaning.

Then I like to open the throttle a little bit and spray more in there to clean out the intake more.

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#21 SubeeTed

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Posted 28 November 2011 - 08:46 AM

Thanks for the reply Porcupine 73 !!
What do you mean by top end cleaner ? Will carb cleaner work ?
Again, many thanks, SubeeTed

#22 the3rsss

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Posted 28 November 2011 - 08:48 AM

Im kinda reaching here, but how about a leak or crack in the booster vac line AFTER the check valve? It would run fine at idle etc but breaking would cause the leak to open up. Also, not sure what the effect would be if the booster check valve were stuck open, Would be simple to check.

#23 SubeeTed

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Posted 28 November 2011 - 08:57 AM

We checked all the lines before and after installing the new reman brake b ooster, all are fine.
Thanks !

#24 porcupine73

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Posted 28 November 2011 - 09:21 AM

For top end cleaner, GM top end cleaner is popular. I think that is what Subaru used to recommend for a while when they were partly owned by GM.

Subaru also has their own stuff: http://www.subarupar...hp?partid=17759

Such as 'Subaru throttle plate and induction cleaner'.

I usually just use Valvoline throttle body cleaner since it is pretty cheap for a big can, most parts stores have it, and it seems to work OK.

Some of the later vehicles have a Teflon or similar coating on the throttle body and plate, so you have to be very careful in what you use to clean those and not use any brushes that could damage the coating.

#25 SubeeTed

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Posted 03 December 2011 - 08:06 AM

Hi ALL !
I tried cleaning the throttle body with Valvoline TB cleaner. It was dirty, the air cleaner was dirty, needs replacing. I gave it a good bath, stalled it a few times, cleaned it up. BUT, it still stalls under hard breaking. So, will the procedure below work on my 2001 Legacy GT with the SOHC ? Or is a different IAC ?
Many thanks, HELP !
SubeeTed
http://forums.nasioc...ad.php?t=781242




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