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Weird Idle

nisskid

By nisskid,
in Engines & Forced Induction

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nisskid Grand Master

nisskid

Posted
Posted

a while back when i got my car it started with this annoying idle where it revs up and down between 1-2.5krpm. to combat this annoying noise i lifted the idle to around 2.5krpm and it would just stay there. i have tried a few things like cleaning the AFM and cleaning/swapping the idle controller over. cleaning the AFM didnt do shit, then tonight i have figured that im pretty sure its not the idle controller.

so yeh any ideas to try?

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zoom Community Regular

zoom

Posted
Posted
a while back when i got my car it started with this annoying idle where it revs up and down between 1-2.5krpm. to combat this annoying noise i lifted the idle to around 2.5krpm and it would just stay there. i have tried a few things like cleaning the AFM and cleaning/swapping the idle controller over. cleaning the AFM didnt do shit, then tonight i have figured that im pretty sure its not the idle controller.

so yeh any ideas to try?

have you tested with different AFM?

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r_speedfreak_r Proficient

r_speedfreak_r

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if youv got an atmospheric bov dont overlook that. when i first purchased my car it used to fluctuate in revs and sometimes when i was driving it would stall & i found out it was becasue the spring tension on my bov was to soft. havent had a problem since. now i got all new issues :S

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The Dan Grand Master

The Dan

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If none of that works, clean out your throttle body. If you dont have an oil catch can, you might want to get one.

What is an oil catch can going to do for him?

Your O2 sensor controls idle settings, then after around 1500-2000rpm the AFM takes over. The AFM is a very likely cause but don't rule out something simple like an O2 sensor.

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cogs Experienced

cogs

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Sometimes when my car is cold the revs will kind've stick.. like idles at 1100rpm (i think, this is when its cold) then I reverse out my driveway and the revs wont go back to 1100rpm, stays close to 2k (no accelerator) then will sometimes drop back down to 1100rpm..

Would this be a similar thing?

Thanks.

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platinum Collaborator

platinum

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Yeah mine seems to be doing the same thing, not reving quite so high, but constantly on-off when idling from 600rpm -> 1200rpm.

Cleaned out the AFM tonight, and took it apart, resoldered the joints (one was very crappy and broke off when i touched it with a screwdriver!) - but put it back on again, and the farking thing was still doing it.

Your O2 sensor is just after the turbo in the dump pipe, I've got a spare one I'm going to try tomorrow, even though the voltages seem to be fine. :

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rob82 Mentor

rob82

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Posted
What is an oil catch can going to do for him?

Your O2 sensor controls idle settings, then after around 1500-2000rpm the AFM takes over. The AFM is a very likely cause but don't rule out something simple like an O2 sensor.

How the hell does your 02 sensor control idle settings?

Its easy to test for a fouled IAC, all you have to do is crimp the hose that feeds it from the intake pipe with a soft pair of pliars, if the revs drop then thats your problem if it doesn't then there is air getting in somewhere else. Make sure your BOV is fully closed and all IC pipes are tight. If there it is still holding high the cold idle up valve under the manifold can sometimes f**k up too. You can check this by crimping the hose feeding it too. If the idle is sitll high then check your intake manifold gaskets.

You guys have got to remeber that the AFM cannot make for a high idle especially not 2000 rpm. The only way this is possible is if the ECU thought it was pulling more load then what it was therefore addressing a higher airflow ignition number. Now a dirty AFM will casue a lumpy idle as the airflow signal usually reads less when it is dirty so the car runs lean. If anything the 02 sensor would attempt to cover this as it will trim more fuel in to get it back to stoich. The biggest sign that your AFM is carbonised is during a hot start condition as there is no cold enrichment and it will take about 10 -15 seconds for the 02 sensor to wake up and do its thing.

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nisskid Grand Master

nisskid

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Posted (edited)

^^cheers for that.

i have got the feeling that it is a vacum leak, as it really happended after i got it back from a dyno mechanic. im thinking they may have fiddled around with things and maybe left a hose or something loose or somthing :P

Edited by nisskid
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  • 3 years later...
HoWiE_Au Collaborator

HoWiE_Au

Posted
Posted

Ive gott a good hunch its a vacuum problem, Mate im having the same problem and all my Vacuum lines are up the shit including the ones to my Charcol canister. Does anyone have any good diagrams or able to get some pictures of all the lines in the engine bay for us please please please :(. If you give your car some herbs and u hit the BOV and take your foot off the pedal does the revs drop heaps . Ive had mine hit BOV release time took the foot off the pedal and had it STALL and its p*ssing me off. Any ideas peoples?

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