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Old 04-07-2009, 12:00 AM   #1
ZOMBIEWAGON02
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Default Rough idle

Since I got my car it has idled hard, i did a tune up with all the basics, CEL came on and got a knock sensor, so I replaced that. it has slowly started to get worse, its less when not in gear but still kinda rough, what would cause this?? I dont want to get taken for a ride at a shop but dont want to keep this going in the wrong direction. Any advice???
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Old 04-07-2009, 12:15 AM   #2
formula91
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Have you cleaned the IACV
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Old 04-07-2009, 12:19 PM   #3
XanRules
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Quote:
Originally Posted by formula91 View Post
Have you cleaned the IACV
the what?
Answering for him, I don't know what it is either, though
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Old 04-07-2009, 02:02 PM   #4
ZOMBIEWAGON02
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WHAT HE SAID^^^^

The what???
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Old 04-07-2009, 02:06 PM   #5
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IACV = Idle Air Control Valve

There's a thread on doing it.
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Old 04-07-2009, 05:03 PM   #6
fastenova
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Give us more information.

Manual or auto trans. (I'm assuming auto by your "not in gear" comment)?

How many miles on the clock?

How does it perform under part/full throttle? Do you notice a lack of power? Has the CEL come on since you replaced the knock sensor?

How long have you had the vehicle?

And, finally, you said "tune up with all the basics." This means different things to different people. Could you elaborate on what was replaced/inspected?

Aaron
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Old 04-07-2009, 08:43 PM   #7
ZOMBIEWAGON02
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Its an auto, with 75k on it 2002 it seems some lack of power, no CEL since the swap, I got the vehicle in JAN/FEB 09 i did sparks oil filters through out, minus trans. and checked removed the cat to check the screens. I found today that the airbox was not on all the way it wasnt snapped at the base so I made sure to fix that.
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Old 04-07-2009, 09:12 PM   #8
RaceFaceXC
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unmetered intake air will cause some poor performance and idle most likely. After you fixed the airbox, did you drive it for a while or reset the ECU? Your fuel trims are probably all messed up.
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Old 04-08-2009, 12:50 AM   #9
williaty
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Hey, you may had a rough idle, but at least you have an idle. That's one better than me right now.
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Old 04-08-2009, 01:32 AM   #10
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My moms '99 OB has a rough idle while stopped in gear. Diriving it is fine.No CEL. No loss of power at all. Changed: fuel filter, plugs, wires, pcv, air filter- made no difference. Haven't had time to clean iacv. That's the last step before I give up. I also noticed that the idle is worst if you come to a quick stop as opposed to slowly braking over a longer distance. Read through countless threads about cleaning iacv--some said it worked others didn't have luck. Looks to be a 50/50chance of success.
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Old 04-08-2009, 01:38 AM   #11
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I need to find that IACV thread - I've got the same problem.
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Old 04-08-2009, 10:32 AM   #12
fastenova
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In another thread you mentioned using Autolite plugs. I haven't personally used this brand in a Subaru, but I'll tell you this: When I bought my car it had Champion plugs in it. Didn't idle very smoothly. I installed some Bosch platinum plugs. Big mistake. Something about the Bosch plugs (and this is well documented in the service and maintenance forum) makes our cars run like crap. I had a lot of hesitation, and an extremely rough idle. I pulled the plugs, check the gap, check all my plug boots, still had the problem.

I swapped them out for NGK V-Power copper plugs, and it ran perfect. I use these plugs exclusively now.

I use Bosch plats on my Ford truck and love them, but they're just no good for our motors, IMO.

So, perhaps try using a different plug. Did you replace the fuel filter? I agree with cleaning the IACV.

Are 2002 vehicles MAP-based? If not, you can try cleaning the MAF sensor. Lack of power can be caused by running a little lean due to a dirty MAF.
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Old 04-08-2009, 10:31 PM   #13
ZOMBIEWAGON02
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where do i get these ngk v power and what is maf?
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Old 04-08-2009, 10:34 PM   #14
ZOMBIEWAGON02
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Quote:
Originally Posted by RaceFaceXC View Post
unmetered intake air will cause some poor performance and idle most likely. After you fixed the airbox, did you drive it for a while or reset the ECU? Your fuel trims are probably all messed up.
how do i do this???
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Old 04-09-2009, 12:20 AM   #15
fastenova
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You should be able to pick up v-power plugs at any decent auto parts store. Napa, Checker/Schuck's/Kragen, AutoZone, etc. My motor takes a BKR5E-11, yours should be similar. You should be able to look it up on NGK's website.

If you don't want to have to change plugs as often you can run the NGK Laser Platinum plugs, but they're around $50 a set. V-powers are like $8-10 for four. I don't mind changing them, so I go for the copper plugs.

MAF is mass air flow, usually referring to the sensor itself, but it's a technology that approximates air flow based on a thin wire with a known resistance/current flow. As more air flows past the heated wire, it cools it and changes the resistance.

Anyway, the MAF sensor is the electronic device in the round intake pipe in between the air filter and the throttle body.
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