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2012 Forester Automatic
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58 Posts
Discussion Starter · #1 ·
Hey Folks,

This is technically on a 2008 Impreza 2.5i Manual Trans with 39,000 miles on it. I've asked over at nasioc as well but haven't heard much so I thought I would ask here :biggrin:

After the car has warmed up, when I push in the clutch and brake to slow down to a stop, the RPM's will occasionally dip really low (i'd say 400 at the lowest) to the point where the car sometimes stutters a bit, then it immediately jumps back to where it should. It doesn't happen every time, and I haven't had it happen when the engine is cold (blue light on).

I cleaned out the throttle body (didn't remove it) but it didn't seem to help. The spark plugs are about 9k over and I have plans to replace them in the next couple of days, but I don't think they would cause the RPM drop (please correct me if i'm wrong). I've also had the alternator tested at two different places and it came back normal. I thought about swapping the MAF sensor out of my 2012 forester, but the part numbers are slightly different so I don't think that will work.

Does anyone have any ideas of what this could be? I haven't had ANY check engine lights so i'm having issues narrowing this down. Any help would be greatly appreciated!!
 
G

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I'm having this problem too, except they drop even lower and sometimes almost stall. Fuel filter? That would be premature at 39K miles.

Try cleaning the MAF sensor.
 

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2012 Forester Automatic
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58 Posts
Discussion Starter · #3 ·
I'm having this problem too, except they drop even lower and sometimes almost stall. Fuel filter? That would be premature at 39K miles.

Try cleaning the MAF sensor.

Should have mentioned that I tried this. :biggrin: No change.
 

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2012 Forester Automatic
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58 Posts
Discussion Starter · #7 ·
I replaced the spark plugs this weekend. No change other than a smoother idle.

I did notice that this only happens when i clutch and actually take the car out of gear. If i leave it in, say, 4th gear and clutch to coast to a stop it drops to about 800. If I clutch then move the gear selector to neutral then the rpms drop low.
 

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2014 Impreza Ltd CVT
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2012 Forester Automatic
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58 Posts
Discussion Starter · #9 ·
Interesting. I'll see if my code reader is capable of checking this. I haven't had any codes thrown making this difficult to diagnose. I may just replace this as it seems to be a reasonably cheap part. I'll let everyone know what i find.

Thanks!!
 

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2012 Forester Automatic
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58 Posts
Discussion Starter · #10 ·
I should ask quick though, are the neutral safety switch part numbers for automatics/manuals typically the same? I did a few checks around and it seems like all the ones i'm finding are saying "With Auto Trans".
 

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2019 Crosstrek 2018 XT
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14,717 Posts
I never used my clutch when coming to a stop. I Just let it slide out of high when the rpms allow it (putting no pressure on the synchronizers). That might help.
 

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2007 Forester Sports XT Manual
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219 Posts
Does it happen if you have the car in neutral with your foot off the clutch or does it only happen when you brake and clutch at the same time?
 

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2012 Forester Automatic
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58 Posts
Discussion Starter · #15 ·
Does it happen if you have the car in neutral with your foot off the clutch or does it only happen when you brake and clutch at the same time?
I tried this on my way home. I really didn't notice the rpms dropping really low while doing this. Mostly it happens when the gear selector is in neutral with the clutch in. I'm usually braking during this. Also, today I did notice an rpm dip while the gear selector was in 1st when I was pulling into a parking spot.
 

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06 forester x 5 MT
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73 Posts
About 5 yrs ago, I had this problem also. I disconnected the battery for overnight. Reconnected it the next morning and turned the key all the way on but did not crank it!! I counted to 5 then started the engine. I have not had the problem since. A Subaru tech told me it was some sensor? that had to be reset and be allowed to position its self before starting.
 

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2012 Forester Automatic
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Discussion Starter · #18 ·
About 5 yrs ago, I had this problem also. I disconnected the battery for overnight. Reconnected it the next morning and turned the key all the way on but did not crank it!! I counted to 5 then started the engine. I have not had the problem since. A Subaru tech told me it was some sensor? that had to be reset and be allowed to position its self before starting.
I've disconnected the battery before in the past and pumped the brakes to get rid of the charge, but I've never actually let it sit for more than a couple minutes so its possible it never drained completely. I'll be heading out for a day or two so I'll disconnect it tonight and let it sit until Sunday.
 

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2012 Forester Automatic
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Discussion Starter · #19 ·
Well after letting it sit for a few days with the neg terminal disconnected (and lights on for good measure) and starting it back up (with the 5 second delay), it seems to be better. I really didn't notice the RPM dip at all this morning. I'll run it for a few more days and let everyone know if this did the trick.
 

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Well after letting it sit for a few days with the neg terminal disconnected (and lights on for good measure) and starting it back up (with the 5 second delay), it seems to be better. I really didn't notice the RPM dip at all this morning. I'll run it for a few more days and let everyone know if this did the trick.
did it solve your issue im having same problem
 
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