BMW REV PROBLEM when idle

[bmw messed up]

hello peoples. hope you all okay and I want to appreciate that you helping out peoples like me.

I have a BMW 2002 316ti se compact. petrol and converted on lpg.

problem just started recently. when I start my car, it rev on 1000rpm for a min then drop down 600-700 rpm. but while driving and car temperature goes on normal. then if i idle my car, the rev's start playing about.
the goes on 1000rpm and goes to 1600 rpm, then drop down to 1000rpm, the goes to 1600rpm. this procedure goes on and on, every after 15-10 seconds.
engine management light came on as well, but i don't know if it is because of rev problem or because of LPG converted. but rev problem happens while driving on petrol or lpg.

car drive good, i recently drove on 100mph, it worked fine. but only happens when its idle.

pleaseeeeeee can one tell me what problem is it ?

[Ivan413]

Could be the sign of a bad o2 sensor(s)


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[Ivan413]

Or your maf sensor


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[bmw messed up]

Originally Posted by Ivan413

Or your maf sensor


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if MAF sensor is bad then car should go in limp mode, if am right?

[Ivan413]

Yeah most likely enter limp mode have u experienced loss of power?


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[Ivan413]

If you haven't experienced power loss I'm guessing u might have a vacuum leak somewhere.


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[Ivan413]

Sorry my phone bugged up and posted it twice


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[bmw messed up]

Originally Posted by Ivan413

Sorry my phone bugged up and posted it twice


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nope it didn't go in limp mode at all. i recently hit 100mph, it runs smooth.

just now, i was looking into it. there is air intake box, it got a small hole because of pulley rubbing.

i found this link, it is exactly the same. 2002 E46 316ti Air filter Lower Box Damaged?

do u think, it can cause revs goes up and down?
plus i got a maf cleaner, i just sprayed the sensor too.

[Ivan413]

I don't think it's your maf at all. You might as well check ur intake box and ur vacuum box for holes .


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[bmw messed up]

Originally Posted by Ivan413

I don't think it's your maf at all. You might as well check ur intake box and ur vacuum box for holes .


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hey thaks for your mail back

vacuum box is the big box in which maf is fixed?

i took the both boxes out and looked for any other holes, but only found one, which i already mentioned and super glued it with plastic, it is fine now. i also cleaned the maf with maf cleaner. all pipes were intact.
i drove the car, firstly the rev's were really bad. it was n 600, i felt like engine gona stop.
after drove little bit, everything since to be fine. but after i put engine on idle. revs start going up again but not that quick as it used to before.

it is same on petrol and lpg.

what else do u think it could be?

[Ivan413]

How many miles does ur bmw have ?


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[bmw messed up]

Originally Posted by Ivan413

How many miles does ur bmw have ?


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milage is 64000

[Ivan413]

Oh ok I was gonna say that it could be you idle control valve is dirty with all the built up carbon because your suppose to clean that about every 80k ...so it's your choice if you wanna take some q-tips and rubbing alcohol and clean that up if it looks dirty and hopefully that solves the idle problem in the mean time I'm gonna research your problem further and ill tell u what I come up with


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[bmw messed up]

Originally Posted by Ivan413

Oh ok I was gonna say that it could be you idle control valve is dirty with all the built up carbon because your suppose to clean that about every 80k ...so it's your choice if you wanna take some q-tips and rubbing alcohol and clean that up if it looks dirty and hopefully that solves the idle problem in the mean time I'm gonna research your problem further and ill tell u what I come up with


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thankyou mate.

i got a small up date. the rev's working little better then before. if i say out of 100%, its 50% better now.

today i opened the box in which maf is fixed and the box underneath, where i fixed the hole.
u mentioned idle control valve, how shall i reach there?
is it close to where i went so far?

other question i need to ask, if i do the diagnostic check, will is show anything?

the check is 40quid here and labour is more in manchester. soo would be really thankful if u can point out how to fix. i will try to do it myself.

[Ivan413]

Yeah the IDV is near where you have been working. Just a little bit further and I'm hoping this solves your problem I have some pictures of diagrams of how to get to it.


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