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Old 07-18-2012, 03:21 PM   #1
isk8emerica87
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Default low and rough idle and stalling at complete stops.

Ok here it is: I have a 2005 rs. My car was running perfectly until I disconnected the negative battery terminal to install fog light bulbs. I reconnected it ten minutes later when I was done and tried to start my car and it died. I started it again and the idle was rough so i let it run for 15, then ran the a/c and such. I then proceeded to take it on a drive. When in motion everything feels ok, However, when i come to a stop with the clutch in it dies out. I have tried a numerous amount of things to figure this out including unhooking the negative terminal for an hour then reconnecting it in hopes of trying to get my car to re-learn it's idle. I cleaned my MAFsensor and made sure all my hoses and plugs were still intact. For the past 3 days my car has been running like ****. I took it to my friends shop and they hooked up the scanner to it; no codes, no cel, no nothing. He said that he re-flashed- the idle air control unit and I should go through certain motions to have my car re-learn its idle but so far nothing has worked. I'm about to tear all of my hair out. Anyone have any insight?
P.S.: Last night i drove my car for 10 min, let it idle for 5 and the check engine popped on, while the "cruise" light simultaneously flashed on and off. I got home and disconnected the battery again and this morning took it to get it scanned again but the CEL and cruise lights were then off.
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Old 07-18-2012, 03:32 PM   #2
GrundleJuice
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After resetting the ecu, turn key to on/run for 20 seconds then back to off. Then start it and allow it to idle for 8-10 mins without touching the accel pedal or putting any significant load on it like a/c, head lights, power windows or even changing manifold pressure by applying the brakes. When engine speeds are rapidly falling toward idle like when depressing the clutch after decelerating in gear, the ecu has to signal the injectors to inject fuel to "catch" it before it gets all the way to idle speed. I assume this is a learned part of the ecu logic since it gets better after some time. If you have a aftermarket or modified intake it may take longer or be impossible to get perfect

anytime you disconnect the battery it resets the ecu and therefore clears any codes. If you want to find out what dtc was triggering a cel you should not reset the ecu first.
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Old 07-18-2012, 04:29 PM   #3
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I do indeed have an injen CAI installed. I shortened up the cold air extension and Im going to give your advice a go in a few here.
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Old 07-18-2012, 07:20 PM   #4
GrundleJuice
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Quote:
Originally Posted by isk8emerica87
I do indeed have an injen CAI installed. I shortened up the cold air extension and Im going to give your advice a go in a few here.
Make sure you have no leaks after the maf sensor
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Old 07-20-2012, 01:33 PM   #5
isk8emerica87
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No leaks. No cel. No weird noises. Just my car still stalling out on me and not holding its idle.

Last edited by isk8emerica87; 07-22-2012 at 02:22 PM.
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Old 07-20-2012, 02:30 PM   #6
GrundleJuice
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Sounds like you need to log the ecu and see what the o2 and MAFv are doing and look at the fuel trim in the A range.
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Old 07-20-2012, 03:37 PM   #7
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I had the same problem, anytime the clutch was engaged when down shifting or stopping the car would drop down to 200 rpms and die. I took it to a local subi guy, and he cleaned the throttle plate and disconnected the battery for an hour. The car idles perfect now.
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Old 07-20-2012, 07:52 PM   #8
SubaruTech84
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After disconnecting the battery your ECM loses its' idle point. You need to go ahead and disconnect the battery again. Then when you hook it up, turn the key on for 5-10 seconds before cranking. Start it up and let it sit about 10 minutes at idle so it can relearn idle. If it still doesn't work you will probably have to clean the throttle blade on the throttle body cause it is probably gunked up and won't allow the blade to come to full "seat" position letting it relearn the idle. I just did head gaskets on my forester and had the same problem. It set the CEL for a P0506 "Idle air control system lower than expected". Try it out and lemme know. HTH
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Old 07-21-2012, 06:25 AM   #9
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I have something similar, the car idle pulses but only when its hot and ive done a few stop start trips, surges a few times and then seems ok. Had the throttle body cleaned but hasnt helped, wonder if resetting the ecu will help.
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Old 07-22-2012, 02:22 PM   #10
isk8emerica87
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Ok so a little update: after spending an hour testing my car with the scanner this is whats going on: something is wrong with my MAF and my idle air control unit which i assume is apart of the MAF. My computer is reading my air intake temp is 28 degrees on a 100 degree day. The problem seems to lie at the mass airflow sensor. I swapped mine out with a friends and my MAF worked fine in his car but his didnt bring mine back to par. I guess now I have to check the harness that plugs into the MAF and the computer as well to make sure nothing came loose. HArd to believe all this stemmed from installing some cheap ebay yellow fog light bulbs. I know that disconnecting the battery causes the ecu to reset, but the problem is bigger than just re-learning idle.

Last edited by isk8emerica87; 07-22-2012 at 02:28 PM.
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Old 07-24-2012, 12:37 PM   #11
colorfull
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There is no IAC on 2005+ imprezas. About the temp reading, are you sure you're not reading in Celcius instead of Farenheit?
Have you tried cleaning your throttle body? I had a similar issue on my 2005, and cleaning the throttle body was the definitive solution in my case. Took me less than 30mn from start to finish.
http://forums.nasioc.com/forums/show....php?t=2358410

Last edited by colorfull; 07-24-2012 at 01:37 PM.
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Old 07-24-2012, 03:16 PM   #12
SubaruTech84
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Trust me - try cleaning your throttle body plate, etc and see what happens. What is it going to hurt at this point? I see it all the time at the dealer after clearing memories.
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Old 07-24-2012, 08:29 PM   #13
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I am dropping it off at a local Subaru mechanic tomorrow. I will try to clean the throttle body plate before then. How exactly would I go about cleaning it? Where exatly is the throttle plate located? And yes I'm sure the scanner read fareignheight. Would unplugging my fog bulbs serve me and justice perhaps? Thank you everyone for your help
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Old 07-25-2012, 09:29 AM   #14
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The throttle body is bolted to the firewall-side of the intake manifold. All you have to do to gain access to the throttle plate is - take the air intake off and the throttle plate will be right there. You will have to hold it open by hand and take a rag with some carb/brake clean on it and wipe the area of the body where the plate closes on it. Also clean the face and edge of the throttle blade itself. Try to clean the hinge points of the blade also. What is happening is that when your ECM tries to relearn the idle the plate cannot close all the way due to the gunk build up. Clean it off, clear memory and see..
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Old 07-25-2012, 02:22 PM   #15
isk8emerica87
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Will do right now. Stand by.

Last edited by isk8emerica87; 07-25-2012 at 02:50 PM.
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Old 07-25-2012, 02:56 PM   #16
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About to start it up after cleaning the throttle body plate. I feel like an idiot in regard to the air intake temp. The 28 degrees WAS in celcuis, but nevertheless the diagnostic paperwork said it should be reading at 40 degrees celcuis. Hope this works either way.
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Old 07-25-2012, 03:17 PM   #17
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Started her up and let her run for 15. Turned on the AC, lights, and radio and all is well! Idling properly now and doesn't die when I rev the motor and the rpm's drop back down. Havnt driven it yet due to it raining and my car was just completely painted but when it dries I will take it for a spin. Thanks subarutech for all your help. You just saved me alot of money!!
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Old 07-29-2012, 09:47 PM   #18
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So did that work? I have a really similar problem as you.

Thanks!
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Old 08-04-2012, 02:57 PM   #19
isk8emerica87
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PULMEOVR, yes it did work. Give it a try!
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Old 08-06-2012, 02:14 PM   #20
JohnM10
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I am planning on cleaning mine. Would it be better to remover the entire TB so that I can spray it with cleaner?
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Old 08-06-2012, 06:03 PM   #21
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Quote:
Originally Posted by JohnM10 View Post
I am planning on cleaning mine. Would it be better to remover the entire TB so that I can spray it with cleaner?
This is how I did mine, it's only 4 bolts and if you're carefull you will not need a new gasket.
Allows you to clean it a lot better than just using a rag with the throttle body on the header.
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Old 09-07-2012, 12:43 AM   #22
generationfourth
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I'm bumping this thread as I had the same problem with my 2007 Subaru 2.5i. I took it to my mechanic to get some maintenance done (plugs, oil, valve adjustment). I went to drive away and the car wouldn't keep idle. I didn't blame my mechanic and we agreed that is was purely coincidental.

He had the car for 1.5 more days and I had to get a rental. He couldn't figure it out and I was getting frustrated with his trouble shooting– "I hate these new cars everything is built in together, I'm trying to find a complete intake/tb/air intake manifold from a junkyard"

Anyway I finally just did the research myself and after I found this thread I called him and told him to clean the TB, to which he responded "yeah I just started doing that, I'm ahead of you" (he hates when I give suggestions).

And now it works perfectly. Wish I would've found the thread earlier I could've done it my self. Thanks guys
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Old 05-16-2013, 12:54 AM   #23
Shlondy
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Quote:
Originally Posted by FMBandit View Post
I had the same problem, anytime the clutch was engaged when down shifting or stopping the car would drop down to 200 rpms and die. I took it to a local subi guy, and he cleaned the throttle plate and disconnected the battery for an hour. The car idles perfect now.
same problem, did the same thing, it fixed it for a while but a few days later... rough idle
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Old 05-16-2013, 03:08 PM   #24
RallyB
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Its deff the throttle body and plate, my 07 did that to me after I took my cosmo short ram intake off and went back to stock. No more fancy intakes for me unless I go turbo
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Old 09-15-2013, 07:38 PM   #25
usmanshiekh
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Holy moly I have to try this now!!
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