Subaru Outback Forums banner

1 - 10 of 10 Posts

·
Registered
2009 Outback 2.5i Special Edition
Joined
·
66 Posts
Discussion Starter #1
On a 2009 OB 2.5i AT, did the routine 60K plug change yesterday and now the idle RPM seems low. Everything else is fine, accelerates fine, has same power, but I'm noticing a small stumbling as I come to a stop. In the last 2 seconds before the car is stopped, seems like the rpm drops too low. Also, in gear with foot on brake, rpm is at about 650. According to the manual, spec is 700 +/- 100.

Car didn't have any issues before this and the only other thing I did was pop in a new air filter, since I had the air box pulled out of the way. I used stock NGK FR5AP-11 replacements and didn't use a torque wrench, rather just did the "snug it up" til the washer seats, then go another 1/4 turn. What went wrong?
 

·
Premium Member
2001 VDC/SC One of a Kind
Joined
·
14,436 Posts
check the fitment of the air box and did you clean the throttle body? Carbon on the throttle plate effects the actual position vs sensor position on the electronic throttle control. Cleaning the throttle generally corrects idle issues.
 

·
Registered
2009 Outback 2.5i Special Edition
Joined
·
66 Posts
Discussion Starter #3
check the fitment of the air box and did you clean the throttle body? Carbon on the throttle plate effects the actual position vs sensor position on the electronic throttle control. Cleaning the throttle generally corrects idle issues.
Air box looks okay. Didn't touch the throttle body. But idle was smooth and seemed normal just prior to changing the plugs.
 

·
Premium Member
2001 VDC/SC One of a Kind
Joined
·
14,436 Posts
New plugs changes the combustion, improving it. There would be a change in fuel trim learning, but Subarus do this constantly when the ECM sees a change in performance or need based on your driving.

Try cleaning the throttle plate/body and see if it improves. Use soft bristle toothbrush to "scrub" any heavy buildup away. It may be difficult to start the first time after cleaning it due to a build up of the chemical in the intake. CRC is a good cleaner safe for electronics.
 

·
Registered
2008 Outback 2.5i AT
Joined
·
202 Posts
did you forget to re plug in the electrical plug after putting the air filer box back together. I just replaced my engine air filter last week and forgot to do this. Plugged it in after my wife came back from a short trip.

Another thing to check is to make sure that you pushed the plug wire boots down hard enough till it pops on. Did you check the gap on the plugs before installing?
 

·
Premium Member
2001 VDC/SC One of a Kind
Joined
·
14,436 Posts
did you forget to re plug in the electrical plug after putting the air filer box back together. I just replaced my engine air filter last week and forgot to do this. Plugged it in after my wife came back from a short trip.

Another thing to check is to make sure that you pushed the plug wire boots down hard enough till it pops on. Did you check the gap on the plugs before installing?
That plug is the Air Temperature Sensor.
 

·
Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
Joined
·
16,140 Posts
Look for a broken retaining clip (plastic) at the indivdual coil/wire connectors at each cyclinder. If broken, it may me arch-ing but not misfiring/enough to throw a code.
 

·
Registered
2009 Outback 2.5i Special Edition
Joined
·
66 Posts
Discussion Starter #8
New plugs changes the combustion, improving it. There would be a change in fuel trim learning, but Subarus do this constantly when the ECM sees a change in performance or need based on your driving.

Try cleaning the throttle plate/body and see if it improves. Use soft bristle toothbrush to "scrub" any heavy buildup away. It may be difficult to start the first time after cleaning it due to a build up of the chemical in the intake. CRC is a good cleaner safe for electronics.
Any idea where I can find a DIY guide with photos on how to do this?
 

·
Premium Member
2001 VDC/SC One of a Kind
Joined
·
14,436 Posts
Remove the air box from the throttle body.

Spray the throttle with the CRC or other cleaner and hold the plate open with one hand while brushing with the other. Try to keep the throttle wet and spray liberal to remove the sludge as you go.

Wet a paper towel or sturdy paper shop towel with the cleaner and wipe it down before reinstalling the box.
 

·
Registered
2009 Outback 2.5i Special Edition
Joined
·
66 Posts
Discussion Starter #10
Remove the air box from the throttle body.

Spray the throttle with the CRC or other cleaner and hold the plate open with one hand while brushing with the other. Try to keep the throttle wet and spray liberal to remove the sludge as you go.

Wet a paper towel or sturdy paper shop towel with the cleaner and wipe it down before reinstalling the box.
Thanks for the write-up. May change out the PCV valve while I'm down there. Just found this guide for removing the airbox.
 
1 - 10 of 10 Posts
Top