Strange idle problem

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Sep 23, 2004 | 07:20 AM

SHADO

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Strange idle problem

Hey guys this is a thing that has been occuring to my 92' Legacy since i bought it, but has been happening more often lately. Whenever im sitting in traffic, i will hear my radiator switch on and then the idle will start to go crazy, up and down between around 200rpm-1.2k rpm and the car will feel assif its about to stall, but stops when i get moving again. My guess is that when the radiator turns on it blows air into my air filter(i have a K&N pod air filter in the engine bay) and stuffs up the idle. I thought if this was the case it was normal, but has been occuring a lot more lately, would changing the coolant make the radiator switch on less often?
Any help would be appreciated im starting to get a bit worried and the car gets very bogged down and lumpy while im moving off.

Sep 28, 2004 | 10:11 PM

scoobsport98

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Car Info: 98 Impreza Outback Sport

I always thought my radiator was always on... and I haven't noticed it "blowing air"

???

you mean AC?

Someone please fill me in if I'm off here.

Sep 29, 2004 | 06:49 AM

SHADO

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Sorry i meant when the radiator fans turn on, when im sitting in traffic i hear them switch on, then the rpm's are all over the place till i get moving again(the fans switch off), im starting to think its an electrical problem like the alternator or something...any ideas?

Oct 1, 2004 | 10:01 AM

OKsubaru

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Posts: 30

From: VA

Car Info: 1999 Rally Blue Pearl Subaru Impreza 2.5 RS

My 99 Impreza does something really similar, I have a post on this forum a few spots down. Someone on the forum reccomended that I replace the mass air flow sensor. There happens a recall on this part for my model, and I'm getting that taken care of soon so if it helps I'll let you know. Other ideas I've heard include bad spark plugs and an improper air/fuel ratio.

Oct 2, 2004 | 06:28 PM

SHADO

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I really think this is an electrical related problem, as it only does it when the radiator fans switch on, i notice that that dash lights start to dim also when the fans turn on, its assif the alternator cant supply enough power or something.

Oct 5, 2004 | 10:45 AM

OKsubaru

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Posts: 30

From: VA

Car Info: 1999 Rally Blue Pearl Subaru Impreza 2.5 RS

I got my MAF replaced yestarday and it fixed the problem right up. When my car would do that I would sort of hear something "switch on" under the hood as you put it, and then the rpms would start going nuts. It sounds really similar to what you are describing, so maybe look into that. Swapping out the MAF is really simple- find someone with a similar model/year that uses the same MAF and pop in in your car for a few mins and see if that does the trick. Hope this helps.

Oct 5, 2004 | 06:19 PM

SHADO

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I take it you mean the AFM (Air Flow Meter)? And how much are these things i've heard their pretty expensive.

And why does it only happen when the thermofans switch on? This is what makes me think its an electrical problem.

Last edited by SHADO; Oct 5, 2004 at 06:33 PM.

Oct 7, 2004 | 08:06 AM

OKsubaru

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Posts: 30

From: VA

Car Info: 1999 Rally Blue Pearl Subaru Impreza 2.5 RS

MAF and AFM are the same thing... I guess it has lots of names. They are pricey if you get them from Subaru (~$250+). You can find them used on eBay though for much cheaper, probably around $70-$80. They are very easy to switch out, if you have ever put in an intake, you've practically done it before.

Oct 7, 2004 | 07:44 PM

SHADO

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Correct me if im wrong but i believe that MAF (Mass Air Flow) is a measurement, whereas AFM (Air Flow Meter) is the actual device.
And ya i've played around alot with my intake shouldnt be a problem.

Oct 8, 2004 | 10:23 AM

#10

OKsubaru

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Posts: 30

From: VA

Car Info: 1999 Rally Blue Pearl Subaru Impreza 2.5 RS

You're probably right, I've always heard mine referred to as the "mass air flow sensor" though.

Oct 10, 2004 | 10:18 PM

#11

joltdudeuc

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Posts: 14,983

From: Union City

Car Info: '99 RBP GM6

Quote:

Originally Posted by OKsubaru

The part number: 22794AA000 Air Flow Meter sensor only (courtesy of peaty)

This is about $50 from your dealership, and you can install this in about 15 mins if you have a flathead screw driver, pliers, and 12mm socket (wrench with extension needed to unbolt airbox from car)

Check it out here http://www.scoobymods.com/forums/showthread.php?t=414

-Gagan

Oct 13, 2004 | 06:02 AM

#12

XenoWolf

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Joined: Dec 2003

Posts: 219

From: Tremont, Pennsylvania

Car Info: 1984 Subaru GL Wagon/1999 Subaru Impreza L Wagon

The MAF Sensor is an insturment for measuring airflow.

Also I'm guessing it's an electrical problem as well. If you can find a multimeter you should test various points around your cars electrical system to see if the voltage fluxuates when the fans kick on.

Is the idle problem happening at the same exact time the fans kick on/off? If there is some delay I'd also suspect your temperature sensor. (The fans might be kicking on too late, causing the car to overheat.)

Oct 13, 2004 | 06:10 AM

#13

SHADO

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Yes, the exact second the fans switch on the idle stuffs up, and the second they switch off the idle goes back to normal, im gonna box up the pod next week and see what that does, it may be the fans blowing air into the pod.