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Old 03-26-2004, 07:37 PM   #1
Scooby Newbie
Member#: 45296
Join Date: Oct 2003
Default K&N clogging my Throttlebody??

Last fall I took my wifes '00 Legacy Gt (58k KM) to the dealer because when the engine was cold the revs would not return to idle after pushing the clutch in. Typically the revs would stay at 2500-3000 rpm. Also there was a small hesitation at part throttle regardless of engine temp at ~2800rpm.

There explanations was foggy but here is what they did
"R/R Throttlebody, cleaned the AIC" - warrenty
"Cleaned air filter and intke (k&n)" - 1 hour labour charged to me
Their explanation was that the K&N was over oiled and was causing the the throttlebody/AIC to carbon up. The K&n was installed by the PO and I thought that maybe he did over oil it.

I took the car back the the dealer yesterday as the car was making a burning smell and the rpm issue was happening when cold.
The dealer tells me that it is excessive carbon build up again. The carbon is now building up in the cat to cause the burning smell and they cleaned the IAC motor again. The car has only been driven 1800 KM since the fall service!!!!
They also claimed that the Throttlebody needs to be replaced as it is too dirty to clean to achieve lasting results.

I asked why I paid 1 hour labour to clean the K&N in Oct. when it has happend again already. He said he that oiled filters like k&n are not recommended by subaru and that the oil causes carbon build up.

He said the throttlebody might be covered under a good will warrenty by subaru and I would pay the R/R (1 hour).

I already have scheduled an appointment at the other Sube dealer in town to get a 2nd opinion and he said that he cannot remember the last time they replaced a TB, maybe if the bushings etc were worn out or it was rusted and inopperable.

Any input or similar experiences?

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Last edited by 85258; 03-26-2004 at 07:58 PM.
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Old 03-27-2004, 03:16 PM   #2
Scooby Specialist
Member#: 20444
Join Date: Jun 2002
Chapter/Region: MAIC
Location: Wilmington, DE|Berkeley
2006 Outback 2.5 XT
Garnet Red Pearl 5MT


I used a K&N filter for about 7.5k miles and currently use an oiled PRM filter with my Cobb intake (3k miles). I haven't noticed any carbon buildup on the throttle-body when I last examined it, but this is a good chance to check and make sure that everything is running as it should be. I haven't heard of any extensive problems caused by using an oiled filter, but maybe I haven't been looking in the right places.

If the dealer cleaned and re-oiled the filter the second time, before you had more problems with the IAC and catalytic converter, I'd wager that you might be able to prove that they, too, over oiled-it. Maybe you should talk to the service manager to see if they can cut you a deal.
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Old 03-27-2004, 09:05 PM   #3
Scooby Newbie
Member#: 45296
Join Date: Oct 2003

I have been dealing with the service manager and he is a difficult to get a long with. I had to fight with he to have my clutch covered under warrenty when there was a tSB about clutch shutter. I only take the car there because it is close.
Anyway, he blames it on the K&N and says that Subaru does not recommend oil air filters period.

I will see what the other dealer says on monday.
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Old 03-27-2004, 09:36 PM   #4
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Member#: 14555
Join Date: Jan 2002
Chapter/Region: MWSOC
Location: MI
1995 Impreza L


only way i can think of that much oil in the intake is it coming up through the PCV valve, and it still shouldnt be doing that to this degree.

Ive seen over oiled filter mess up the MAF sensor on some cars, but never enough oil to clog a throttle body.
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Old 03-28-2004, 03:18 PM   #5
Patrick Olsen
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Member#: 120
Join Date: Jul 1999
Chapter/Region: AKIC
Location: Where the Navy sends me...
1997 Legacy 2.5GT
1996 Impreza coupe


Yeah, the dealer's full of it. How in the hell would an over-oiled K&N air filter affect the cat??!!

I'm with Hawk296, if there's that much oil in the intake tract it's probably coming from the PCV system. There simply isn't enough oil in/on a K&N filter to gunk up the system that much.

I've been using K&Ns on my cars pretty much since day one. I had one to fit in the stock airbox first, and now have a cone-style one on the end of Injen intake. No problems in over 110,000 miles of driving.

Definitely see what the other dealer has to say, and see about replacing the PCV valve.

Pat Olsen
'97 Legacy 2.5GT sedan

PS - Having the idle "hang" when it's cold isn't entirely unusual, it has to do with emissions I think as the ECU tries to get the engine up to temp. Does this happen all the time, or only in the first few minutes of driving?
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Old 03-29-2004, 10:14 AM   #6
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Member#: 32846
Join Date: Feb 2003
Chapter/Region: MAIC
Location: Elkton, VA
1998 Impreza L-SOLD
Arcadia Green


I've been running a K&N panel filter for about 12,000 miles and just checked the TB Saturday night. It has remained spotless since I cleaned it 16,000 miles ago. I can see the dealers point of view if you were to dump a quart of 5w30 on the filter, but I don't think anyone does that.

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Old 03-29-2004, 02:42 PM   #7
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Member#: 34670
Join Date: Mar 2003
Chapter/Region: South East
2016 slowmobile


The only problems I know of with over-oiling are on cars with a sensor after the throttle body.
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Old 03-29-2004, 08:20 PM   #8
Scooby Newbie
Member#: 45296
Join Date: Oct 2003

The other dealer in town looked at the car today.

They found no problem with Throttle Body. They were unable to tell how the throttlebody was gumming up before. They cannot understand why the other dealer would want to replace it as everything seemed operational.
They were unable to replicate the burning smell but the tech is driving it home tonight to try and get a few miles in it.

I called the first dealer back and told the service manager the result from the other dealer. He was trying to back track and cover his ass.
Him - "Sounds like you have lost your confidence in us."
Me - "absolutely!"
They are refunding the 1 hour labour and supplies from the October service.

We will see if the problem returns in few thousand miles or not.
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