Jump to content


Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse
 

Photo
- - - - -

SOHC 2.5L with Funky, Cycling idle ???


  • Please log in to reply
19 replies to this topic

#1 subaruVWnut

subaruVWnut

    USMB Regular

  • Members
  • PipPipPip
  • 56 posts
  • California

Posted 14 September 2006 - 02:13 AM

I have a 2002 Impreza 2.5RS engine in my VW Vanagon that has had erratic idle for a couple of months now.

The engine seems to run OK when first started, (cold) until it goes closed loop. Then it idles fine for about three seconds, then stumbles, and struggles for the next three seconds. This cycle repeats indefinitely, over and over.

It seems to run fine when the throttle is advanced to higher rpms.

I'm wondering what sensors might cause this repetitive cycle that I could try replacing.

Oxygen Sensor ?
IAC valve ?
Throttle position switch ?

I have another engine with most of these that I could try switching some of them out.

Any thoughts or tips appreciated.

W

#2 rcoaster

rcoaster

    H6 Power!

  • Members
  • 502 posts
  • Rochester, NY

Posted 14 September 2006 - 05:16 AM

Check the IAC valve. It might be just dirty and can't meter the correct amount of air into the intake.

#3 nipper

nipper

    Semi Elite Master of the

  • Members
  • 17,541 posts
  • Long Island NY

Posted 14 September 2006 - 08:47 AM

what he said IAC controls the idle.

nipper

#4 Storydude1

Storydude1

    USMB is life!

  • Members
  • 167 posts
  • NW AZ

Posted 14 September 2006 - 09:14 AM

X3 on the IAC.

#5 xrturbo

xrturbo

    Subaru Fanatic!

  • Members
  • 368 posts
  • allentown

Posted 14 September 2006 - 09:18 AM

possibly the o2 because in those years they had that goofy o2 sensor with the air flow meter. we just had the same issue last week in an 02 forester.

#6 subaruVWnut

subaruVWnut

    USMB Regular

  • Members
  • PipPipPip
  • 56 posts
  • California

Posted 14 September 2006 - 10:19 AM

possibly the o2 because in those years they had that goofy o2 sensor with the air flow meter. we just had the same issue last week in an 02 forester.


Yes, this engine has an AFM. Can you tell me more about the O2 sensor.

What's "googy" about it? Only extra O2 sensors I have around are from 90-94 Legacy's and a new one from the dealer is expensive to buy.

Warren

#7 nipper

nipper

    Semi Elite Master of the

  • Members
  • 17,541 posts
  • Long Island NY

Posted 14 September 2006 - 10:27 AM

Yes, this engine has an AFM. Can you tell me more about the O2 sensor.

What's "googy" about it? Only extra O2 sensors I have around are from 90-94 Legacy's and a new one from the dealer is expensive to buy.

Warren


The o2 sensors from the aftermarket may not be as relaible or reactive as OE.
If you have two sensors, the first should be OE, the 2nd can be anyones. The first talks directly to the computer and controlls emissions, the 2nd just measures that cat's output.

nipper

#8 cannonball

cannonball

    User Awaiting Email Confirmation

  • Members
  • 205 posts
  • Greenville

Posted 14 September 2006 - 10:39 AM

Nipper do you think that it would be safe to say that more than likely the front O2 sensor can be replaced without worrying about the rear one since most idling problems are related to it's function?

#9 nipper

nipper

    Semi Elite Master of the

  • Members
  • 17,541 posts
  • Long Island NY

Posted 14 September 2006 - 10:43 AM

Nipper do you think that it would be safe to say that more than likely the front O2 sensor can be replaced without worrying about the rear one since most idling problems are related to it's function?


Yes. The front o2 snesor seems to wear out quicker then the 2nd, since the first is exposed to unprocessed fumes.

nipper

#10 subaruVWnut

subaruVWnut

    USMB Regular

  • Members
  • PipPipPip
  • 56 posts
  • California

Posted 14 September 2006 - 10:59 AM

Nipper do you think that it would be safe to say that more than likely the front O2 sensor can be replaced without worrying about the rear one since most idling problems are related to it's function?


A friend of mine who prepares the SOHC 2.5L for use in airplanes and gyrocopters tells me they don't use the second sensor at all since it has no effect on how the engine runs....it only tests the condition of the second CAT to tell if it's functioning or not. Experimental aircraft with Subaru engines don't use any CATs.

I don't currently have the rear 02 sensor hooked up either, since the wire to it fell down onto my muffler and the connector was melted. But the idle symptoms I have now were occuring before that happened....and after...no change. I don't consider it part of the problem, although I get a code for the missing sensor.

Warren C.

#11 subaruVWnut

subaruVWnut

    USMB Regular

  • Members
  • PipPipPip
  • 56 posts
  • California

Posted 14 September 2006 - 11:05 AM

Who has the best price for an OEM front O2 sensor?

My local FLAPs wanted $140.

www.1stSubaruparts.com wants $108 plus shipping.


Any verifiable good results from less expensive aftermarket versions

Warren

#12 xrturbo

xrturbo

    Subaru Fanatic!

  • Members
  • 368 posts
  • allentown

Posted 14 September 2006 - 11:15 AM

i mean it is goofy just by its design in comparison to other designs.

#13 subaruVWnut

subaruVWnut

    USMB Regular

  • Members
  • PipPipPip
  • 56 posts
  • California

Posted 14 September 2006 - 11:43 AM

i mean it is goofy just by its design in comparison to other designs.


I sometimes hear the term "wide band 02 sensor" ?

Is that what this engine has?

What's different about 'wide band" vs any other sensor.

W.C.

#14 ShawnW

ShawnW

    Subaru Master Technician

  • Administrator
  • 12,914 posts
  • Denver, Colorado

Posted 14 September 2006 - 05:05 PM

Try putting a 2.2K ohm resistor in the plug for the 2nd o2. you can buy 5 of them at Radio shack for under a buck or two. Just bend the prongs in and stick it into the terminals.

#15 Wayne Boncyk

Wayne Boncyk

    Subaru Fanatic!

  • Members
  • 354 posts
  • Denver

Posted 14 September 2006 - 05:54 PM

I can give you one good data point for aftermarket O2 sensors. I have bosch generics in both the front and rear spots on my 96 OBW, and they have been working fine for 9+ months now. Given the physics/chemistry of how they work, these aftermarket jobbies might wear out faster, but they'll provide exactly the same voltage variation while there's still enough reactant left in the probe for them to work... so cheaper is OK, if you are willing to trade lower cost for the possibility that you might have to change them out sooner. Again, the Bosch generics work just fine in both positions, at least for my 2.5L exhaust. Passed Colorado state emissions inspectin with flying colors, too -- better numbers than I had on the last test I had done, in California a couple of years back....

#16 xrturbo

xrturbo

    Subaru Fanatic!

  • Members
  • 368 posts
  • allentown

Posted 14 September 2006 - 06:08 PM

they arent gonna work for his style of sensor. of yours is the one i am thinking of it has that flip lever clamp that holds the connector together, it is a completely diff animal than any other you have seen. i dont know alot else about it except is seems to be the new expensive subaru issue that can cause a ton of drivabiltiy problems without throwing a light. we have done a couple so far at work, one last week on a forester and another on an RS that i swapped.

#17 Wayne Boncyk

Wayne Boncyk

    Subaru Fanatic!

  • Members
  • 354 posts
  • Denver

Posted 14 September 2006 - 06:36 PM

Didn't know about that. Sorry for the bum advice!

#18 subaruVWnut

subaruVWnut

    USMB Regular

  • Members
  • PipPipPip
  • 56 posts
  • California

Posted 15 September 2006 - 12:15 AM

it is a completely diff animal than any other you have seen. .



So tell me, What kind of "diff animal" is it?

That's what I'm trying to find out.

"Wide Band" ??? "Narrow Band"?? Something limited that only works with the cars that have an AFM??

Please enlighten me..

Warren C.

#19 xrturbo

xrturbo

    Subaru Fanatic!

  • Members
  • 368 posts
  • allentown

Posted 15 September 2006 - 04:16 PM

i am not completely sure, like i said it is a diff plug setup. from what my boss tells me (so dont quote me on this) if you notice the car has no mass air, he said that sensor also determines airflow along with normal frunctions of oxygen measurements and heating.

#20 xrturbo

xrturbo

    Subaru Fanatic!

  • Members
  • 368 posts
  • allentown

Posted 15 September 2006 - 04:17 PM

i just threw away a bad one today, i wish i would have taken a pic.




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users