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2004 FXT
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14 Posts
Discussion Starter #1
I have a 2004 FXT @ 100K. Engine started to idle at very low rpm, around 5oo and less, to the point of almost stalling. Just had new plugs put in a week ago. I have cleaned the MFA sensor as well as have done the Seafoam treatment. Car runs fine with acceleration above 2000RPM. I also had valve gaskets replaced last week so I am assuming there is no valve damage/problems otherwise that would/could have been detected?...Maybe I need to check coil? Fuel Filter? Fuel pump? I will be picking up a diagnostic reader to get a code tomorrow but looking for other ideas. I know I have a bad rear 02 sensor but maybe front is going? Help!
 

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2004 Subaru FXT MT
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1,841 Posts
pull the codes and start doing the basic maintenance...
 

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Ah crap.. I'm back with my 05 XS
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8,294 Posts
You just did your plugs so you unplugged the car from the battery right? Mine does this too until I drive it for a while, then it gets back to normal, idling just above the thick line below 500.
 

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2005 Forester XT 4eat
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4,581 Posts
Is it manual or auto? My auto idles right around 500rpm when it's in gear. Also what kind of oil are you running? Thicker oil can cause a low idle. Is there an actual drivability problem, or is it just the rpm concerning you?
 

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1998 Forester
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951 Posts
If you disconnect the battery, or even reset the cel, the car may need to relearn a idle. Let the car set and idle for 10 minutes, then a bit longer with the a/c on.
Just did some work on a car; every time I reset the cel it would die when being clutched until it relearned...
 

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2004 FXT
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14 Posts
Discussion Starter #8
I got 4 codes:
rear sensor - already knew about

low input MAF - cleaned but didn't seem to help. Bought a replacement from salvage yeard and wont get until next Monday. FYI, subaru wanted $275 for new part. junk yard wants $75 used. As of now, Im thinking this could be the ticket.

intake air high input poo21 cam position actuator A bank 2 timing over advanced - took this a bit further and found a broken filter in the banjo bolt on only the driver side. passenger side was removed already (It has been suggested that both filters should be removed as well as filter leading to turbo). This has not seemed to help just yet. Info for this can be found on Scoobymods keywords "TSB Rough Idle 04 Turbo motors". Im new here and site wont let me post link.


What are thoughts on resetting ECU? To do this I understand I should try:

disconnect battery cable, let sit for 45+min. then drive "spirited" for a bit. Does this sound accurate?


Thanks for input
 

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2004 FXT
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14 Posts
Discussion Starter #9
sorry, should read like this



I got 4 codes:

p0037 rear sensor - already knew about

p0102 low input MAF - cleaned but didn't seem to help. Bought a replacement from salvage yeard and wont get until next Monday. FYI, subaru wanted $275 for new part. junk yard wants $75 used. As of now, Im thinking this could be the ticket.

p0113 intake air high input?? maybe related to MAF malfunction?

p0021 cam position actuator A bank 2 timing over advanced - took this a bit further and found a broken filter in the banjo bolt on only the driver side. passenger side was removed already (It has been suggested that both filters should be removed as well as filter leading to turbo). This has not seemed to help just yet. Info for this can be found on Scoobymods keywords "TSB Rough Idle 04 Turbo motors". Im new here and site wont let me post link.


What are thoughts on resetting ECU? To do this I understand I should try:

disconnect battery cable, let sit for 45+min. then drive "spirited" for a bit. Does this sound accurate?


Thanks for input
 

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Administrator
2007 Forester Sports XT 4EAT
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40,081 Posts
Just pumping the brake pedal a few times will drain any residual power, so no need to let it sit, unless it's convenient. :wink:

I've always just driven normally after a ECM reset on both our Foresters & never had any issues.

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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2004 FXT
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14 Posts
Discussion Starter #11
Is it manual or auto? My auto idles right around 500rpm when it's in gear. Also what kind of oil are you running? Thicker oil can cause a low idle. Is there an actual drivability problem, or is it just the rpm concerning you?


Automatic and I use full synthetic. engine smooths out after about 200 RPM and seems to drive fine.

After some more tinkering, RPMs now are idling at 1500 RPM, when I put a bit of a load on the RPMs drop to almost stall but then recovers and starts to climb back up. Still a little rough but not as shaky. getting some knocking from engine.

Also, anyone know for sure about Idle Air Control Valves? Some forums say subaru doesnt have one and others say they do. Couple more sensors by Throttle Body in particular throttle position sensor. Would this play any part?
__________________
2005 Obsidian Black Pearl XT w/4eat
 

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2004 FXT
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14 Posts
Discussion Starter #13
Its an 04 and apparently it does have the IACV. I have been getting mixed responses but I know I can find an 04 part online so it must exsist. After lokoing around I might have found it. For those who know for sure let me know if this sounds right:

for non turbo I believe the sensor is on driver side beneath throttle but for turbo it is actually on driver side, base of head and just behind the oil dip stick housing. 2 screws, one on top the other on bottom making that one difficult to get at. I have also read that the 2 screws are tight and soft so easy to strip.
 

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2004 FXT
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Discussion Starter #14
Added a new (used; salvage yard for $75) MAF sensor and does not seem to help. To review, I have received many codes from the start of my problem to now.

p0102-MAF...I stopped getting code after cleaned the original MAF with no change in idle.

I then started to get Misfire codes for all cylinders, 2 and 4 matured where 1 and 3 did not.

After replacing MAF I am now getting codes:
p0037-Rear O2
p0108-MAP sensor high input
P1086-tumble Generator circuit low

All codes are showing matured and Pending (whatever that means)

Would the rear sensor have that much to do with jumpy codes? It seems the O2 sensor is the most consistent issue. I ordered a new sensor and shouldve been here by now but I must wait another day or so I guess.

any other thoughts and ideas let me know

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2004 Forester XT
 

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2005 Forester XT 4eat
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4,581 Posts
What kind of condition are your alternator and battery in?
 

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2004 FXT
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14 Posts
Discussion Starter #17
I think im having issues with Tumble Generator Valve Sensor. I have been looking online with not much luck for the sensor. I have read some threads by "Peaty" that suggests the TPS and TGV can be interchanged and that dealer wont sell just the TGV... Anyone have thoughts on that?
 

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2005 Forester XT 4eat
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Did you replace the battery because it died? Sometimes a weak alternator can cause batteries to die prematurely. You can get your alternator tested for free at autozone. It seems unlikely that all the different sensors could be failing at once. Also, check the condition and tension on your drive belts.
 

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2004 FXT
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Discussion Starter #19
Well, yes. but the battery was only at about 25% and I think I drained it just by working to find the problem. I also started car and unplugged negative terminal and engine continued to run. Belts are new and tension is normal.

I think, but really not sure, that because I have been getting multiple readings, unplugging and plugging battery as well as unplugging all sensors to see effects has skewed the readings. It seems my ECU is having a hard time re- calibrating. thoughts?
 

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2012 Forester FXT automatic
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35 Posts
Solution to low idle after battery disconnection

Greetings all this is my first post. I HAD to register because I know the solution to the low idle problem you are having. I had the same thing happen to me last year after replacing a dead battery on my 2005 Forester. I searched for days on the internet and was about to take the car in and I found this solution that a Subie mechanic had posted on another site.

Disconnect the battery and reconnect. When you start the car for the first time, turn the key to the ON position but do NOT turn the engine over. Wait 10-15 seconds so the electronic throttle body or IACV has time to go to the factory programmed home position. After waiting, start the car and let it idle without any load, lights, A/C etc. Every 20 seconds or so the idle will bump up 50 RPMs. Mine started out at 500 and ended up at 750 (normal for my car) after a few minutes. From that point on, normal driving will allow the computer to optimize further.

I can not believe they don't tell you this info in the manual. No telling how many people have dropped a lot of money replacing parts after a battery change. Good luck and let me know if it works!

Paul
 
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