Engine almost stalls when stopping

Roughly 50% of the time that i pull up to a stop sign or traffic light and press the clutch in the engine will drop down like it's supposed to, but then will almost stall out. It will often drop below the 500rpm mark, which is the lowest one, and sometimes feels like it is going to stall. Car has <8000 miles on it and has been doing it most of it's life. Would this be a simple fix or something bigger?

it sounds like a ECU problem to me. I would take it to a dealership and have them reset the ECU.

i agree.. ur idle must be too low. take it to the shop.

Sounds good, i need to go down for the PZEV reprogramming anyways, so i'll mention it. When idling it's at 750, which i believe is normal, just right when it comes down from higher rpms will it sometimes bog down a bit.

Have you driven any dusty environments ? I tracked down similar issues to one day of driving behind a bunch of rabid Subaru folks which dusted my throttle body. On that particular day we enjoyed a bit too much off road.

My spec B does the same thing on occasion. I'm going to have it checked when I take it in for the 30k service in a month or so. At first I thought it was me, but it's not.

My 05 gt with 91k does the same thing.

I have a 2007 N/A legacy that I've noticed doing the same thing. I'm pretty sure that it started after I had the PZEV recall (Jan. 4th) but I'm not worried about it, honestly. And.... i don't recall it happening recently, say the past 2 weeks.

my 09 does the same thing, i already had the PZEV flash it it did not fix the problem, I did notice it only does it when its cold..

Could be the maf too.

mine has done this since new. very annoying. ive asked the dealership a couple times and they always say theres no reflash or anything so i doubt theres any fix. the latest reflash is the pzev reflash, which should have any previous revisions including. i got it done and nothing changed.

 

heres a video of mine. i took video this at idle with the a/c compressor cycling on and off which also triggers the studdering like when coming to a stop. take note of this sometime.

 

[ame=http://www.youtube.com/watch?v=TJSIbsSnFdw]YouTube- 2008 legacy 2.5i se 5mt, idle drop, shudder issue.[/ame]

Also check for vacuum leaks.

 

And check if there is a difference when you press the brake or not. It may be the brake assist unit that's leaking.

My 2.5i does it too, only when its cold. Nature of the beast.

everyone who has his issue has a pzev correct?

 

according to subaru, the pzev system, fuel injectors that close tighter when they're not in use. so could it be that when you are coasting to a stop in gear, there is no fuel being used. but as you depress the clutch and get out of gear, fuel doesn't get to there quick enough to idle; and with the extra load from braking/steering/etc, the studders almost stalling. thats my guess.

everyone who has his issue has a pzev correct?

 

Nah, I've got an '05, which has the '00-'04 Legacy style catalytic converter. Definitely not PZEV. This issue may not lie in the exhaust. I'm guessing something to do with the airflow metering and how the IAC valve reacts to it.

 

I do remember there being a TSB on this problem and a specific reflash available to fix it, but I can't remember what it is. The dealer should know. Pretty sure it's not PZEV related though.

I had this problem with a 05 LGT, Cobb AP Stage 1. A winter only problem for me. I bumped up the idle rpm by 100 on my accessport and voila! problem solved. You might want to see if someone can raise your idle rpm. I'm not sure how that works with the 2.5i, but it could be a cheap fix attempt.

Happens to me as well. GT with a 5EAT. Started after the dealer worked on my engine. and didn't happen before. 58,2xx. miles here!

 

Extensive description here:

http://www.cobbforums.com/forums/showthread.php?68357-2005-5-idle-issue

 

Sadly, no fix yet. Tried raising the RPM's like above BUT when I put it in D or N, it is too high.

Anyone tried cleaning the throttle body? I've seen this has fixed many of these problems on the NA #oldschoolthreadbump

Anyone tried cleaning the throttle body? I've seen this has fixed many of these problems on the NA #oldschoolthreadbump

 

the new positive battery terminal is better built for a more solid connection. get a new battery if needed. clean and check the coil pack connections.

 

aftermarket bypass valves have been flakey for me. turbo smart kompact and cobb xle. stock gives a more solid more reliable action. stock is actually more reactive. the kompact valves is heavy. cobb is lighter. but they seem slower than stock. no random misfires with stock bpv either. oh...and put some grease/lube on the stock bpv shaft. i think it needs lube like other bpv do.

 

i didnt get stalling but got dropping rpms to 500 from 650. after these changes its been good. soft drop from 750 in N to 650 in D. not a rapid drop then a recover scenario.

 

i do NOT trust aftermarket bpvs.

the new positive battery terminal is better built for a more solid connection. get a new battery if needed. clean and check the coil pack connections.

 

aftermarket bypass valves have been flakey for me. turbo smart kompact and cobb xle. stock gives a more solid more reliable action. stock is actually more reactive. the kompact valves is heavy. cobb is lighter. but they seem slower than stock. no random misfires with stock bpv either. oh...and put some grease/lube on the stock bpv shaft. i think it needs lube like other bpv do.

 

i didnt get stalling but got dropping rpms to 500 from 650. after these changes its been good. soft drop from 750 in N to 650 in D. not a rapid drop then a recover scenario.

 

i do NOT trust aftermarket bpvs.

 

thanks for the reply, i have a friend with a stock 08 automatic and if you come to a very brisk stop his RPM's drop to 150-200, all of his dash lights christmas tree, and then it picks itself back up.

 

we can't think of anything causing it other than reading online that some people replaced the torque converter and the problem went away? i dunno its a weird issue.

 

-Brett

I had this problem on my previous LGT (RIP) - it turned out to be an issue with the AVCS and the fix involved (I think) some kind of repair to the AVCS solenoid (if that sounds right, I can't remember the exact part/terminology).

I had this problem on my previous LGT (RIP) - it turned out to be an issue with the AVCS and the fix involved (I think) some kind of repair to the AVCS solenoid (if that sounds right, I can't remember the exact part/terminology).

 

hmm i believe the avcs solenoids are pretty easy to service and clean! thanks ill check this!

hmm i believe the avcs solenoids are pretty easy to service and clean! thanks ill check this!

 

Solenoid might be the wrong term, just FYI, but it was an AVCS component and it took a Subaru shop to figure that out by logging engine timing. Other mechanics guessed things like oil control valve that weren't a fix. Some AVCS part had to be removed and serviced.