what can cause idle fluctuations?

[scoobygt]

just test driven a 2000 b4 legacy rev c manual and found that when you come to a stop or after giving some revs the idle drops and fluctuates abit, most of the time it\'s alright but it does it every now and again, thanks in advance.

[Stoffa]

Vacuum leak or sticky gummed up idle control solenoid/stepper motor

[Guest]

Above or beginning of afm failure...I think they have the samfe afm as V5/6 well the rev c blitzen does anyway so easy to borrow one and check.

[scoobygt]

okay so nothing to major then cheers chaps!

[Guest]

I would tell them to get it fixed before I bought it. You drop it off to a mech to fix it will cost you a bit if it doesnt have a cel - no code. If you fix it yourself well just do a search people have spent over 1g on idle problems just replacing parts themselves.

[scoobygt]

$1000 for idle problems that\'s abit excessive! must have just been replacing parts whilly nilly or had no clue what\'s going on . . .

[hijacka]

The Idle fluctuation is generally a leak after the afm for which unmeasured air is getting in, which really could be anywhere hence the cost of repair may be high. Could be Intake manifold gaskets, A split hose or a crack plastic intake but its at anyone\'s guess. I would be checking out the plastic under manifold intake and pay special attention on the left hand side as some noob jockey may have replaced the primary turbo and split the rubber boot that goes over the turbo snout.. It could be leaking in a number of places anyway...check to see if its worst or more evident once warmed up, split Rubber, cracked plastic and small gasket leaks will generally open up more when hot.

[94 Leone]

My idle fluctuation is because of the vented stock bov lol I know all the piping is fine cos it\'s new . So check for leaks there too.

[scoobygt]

yeah this one has a super sequential thingy

[hijacka]

 scoobygt said:

yeah this one has a super sequential thingy

With the car on idle put your hand over the bov and see if its sucking in air..

[Joker]

rocking the steering wheel can cause something similar/load

[94 Leone]

Im gunna be slightly bundy and get some rubber and make a reed valve type thing to stop air getting in but it\'ll blow out.

[Joker]

wut

[scoobygt]

yes joker I also tried rocking the steering wheel and it made it drop and stumble about for a second

[Kiwi_Fozze]

I foresee a duck caller attached to that bov....

[Guest]

 hijacka said:

The Idle fluctuation is generally a leak after the afm for which unmeasured air is getting in, which really could be anywhere hence the cost of repair may be high. Could be Intake manifold gaskets, A split hose or a crack plastic intake but its at anyone\'s guess. I would be checking out the plastic under manifold intake and pay special attention on the left hand side as some noob jockey may have replaced the primary turbo and split the rubber boot that goes over the turbo snout.. It could be leaking in a number of places anyway...check to see if its worst or more evident once warmed up, split Rubber, cracked plastic and small gasket leaks will generally open up more when hot.

This but yes people like you op who ask about it generally ask coz they have no idea. Then people say this, this or this and then they go about replacing everything, coils, leads, temp sensor, afm bov, vacuum lines etc and never find the problem. If you have a vented bov it only drops right off when you come off you throttle not at idle I think. Ive run a couple of vented ones in various cars and never had that problem ever.

[twinturboboy]

I bought a 2000 BH5 Legacy TT with idle issues - I replaced AFM and problem solved!!

[94 Leone]

 evowrx']

[quote name='hijacka said:

The Idle fluctuation is generally a leak after the afm for which unmeasured air is getting in, which really could be anywhere hence the cost of repair may be high. Could be Intake manifold gaskets, A split hose or a crack plastic intake but its at anyone\'s guess. I would be checking out the plastic under manifold intake and pay special attention on the left hand side as some noob jockey may have replaced the primary turbo and split the rubber boot that goes over the turbo snout.. It could be leaking in a number of places anyway...check to see if its worst or more evident once warmed up, split Rubber, cracked plastic and small gasket leaks will generally open up more when hot.

/quote]

This but yes people like you op who ask about it generally ask coz they have no idea. Then people say this, this or this and then they go about replacing everything, coils, leads, temp sensor, afm bov, vacuum lines etc and never find the problem. If you have a vented bov it only drops right off when you come off you throttle not at idle I think. Ive run a couple of vented ones in various cars and never had that problem ever.

Unless you\'re venting a bov which is supposed to be re-circed such as the stock bov.(like me) and yes fozze it will be a slighty awesome duck caller gear change haha

[Guest]

 94 Leone']

[quote name='hijacka said:

The Idle fluctuation is generally a leak after the afm for which unmeasured air is getting in, which really could be anywhere hence the cost of repair may be high. Could be Intake manifold gaskets, A split hose or a crack plastic intake but its at anyone\'s guess. I would be checking out the plastic under manifold intake and pay special attention on the left hand side as some noob jockey may have replaced the primary turbo and split the rubber boot that goes over the turbo snout.. It could be leaking in a number of places anyway...check to see if its worst or more evident once warmed up, split Rubber, cracked plastic and small gasket leaks will generally open up more when hot.

/quote]

This but yes people like you op who ask about it generally ask coz they have no idea. Then people say this, this or this and then they go about replacing everything, coils, leads, temp sensor, afm bov, vacuum lines etc and never find the problem. If you have a vented bov it only drops right off when you come off you throttle not at idle I think. Ive run a couple of vented ones in various cars and never had that problem ever.

Unless you\'re venting a bov which is supposed to be re-circed such as the stock bov.(like me) and yes fozze it will be a slighty awesome duck caller gear change haha

No because it would be closed on idle? Its a valve not a hole. Mate put a recorder on his the other day...fuckwit

[94 Leone]

Yeah it\'s supposed to be closed on idle, but the stoock ones are cruddy and let air in. Unless recirc\'dnand I don\'t have the pipe to do it atm lol

[Guest]

 94 Leone said:

Yeah it\'s supposed to be closed on idle, but the stoock ones are cruddy and let air in. Unless recirc\'dnand I don\'t have the pipe to do it atm lol

Tell steve murch that...Im going back to stock when it arrives as per his suggestion.

[scoobygt]

changing the topic, is 25 vac on idle good? my 94 twin turbo has 20

[94 Leone]

 evowrx']

[quote name='94 Leone said:

Yeah it\'s supposed to be closed on idle, but the stoock ones are cruddy and let air in. Unless recirc\'dnand I don\'t have the pipe to do it atm lol

/quote]

Tell steve murch that...Im going back to stock when it arrives as per his suggestion.

Stock has to be recirc\'d.

Mine is stock and not recirc\'d ergo idle fluctuations.

If it is re-circ\'d it will be fine and you don\'t have to worry; otherwise non vacuumed air won\'t be \'holding\' it closed like if it were recirc\'d.

Make sense?

[boon]

I had shithouse idle for ages, was due to deposits on the throttle body stopping the butterfly from closing completely making the idle control stuff freak out. Try hooking your toe under the gas pedal and pulling it up slightly to force the throttle to close properly.

[Guest]

 94 Leone']

[quote name='94 Leone said:

Yeah it\'s supposed to be closed on idle, but the stoock ones are cruddy and let air in. Unless recirc\'dnand I don\'t have the pipe to do it atm lol

/quote]

Tell steve murch that...Im going back to stock when it arrives as per his suggestion.

Stock has to be recirc\'d.

Mine is stock and not recirc\'d ergo idle fluctuations.

If it is re-circ\'d it will be fine and you don\'t have to worry; otherwise non vacuumed air won\'t be \'holding\' it closed like if it were recirc\'d.

Make sense?

No not at all.