525 Idle Revs Itself - BMW Forum

leetman · 08-04-2005, 11:45 PM

When my 1990 525 idles its rpms get really low, almost below 500 then it revs itself a little to about 800 and then drops back to 500 and then up to 800 and so on....

everytime it drops back to 500 it sounds like its going to die and it grumbles to pick iself back to 800 but then of course drops the 500 and does the whole process over and over again.

What is wrong?

sp0rky · 08-05-2005, 02:40 AM

Could be the idle control valve. It's right there on top on the intake manifold connecting to the intake boot.

Try removing it and cleaning it with a carb cleaner or something. If that doesn't work, it may very well need replacement.

tacroteau · 08-06-2005, 12:27 PM

M.A.F.

Quote:

Originally posted by sp0rky@Aug 5 2005, 03:40 AM
Could be the idle control valve. It's right there on top on the intake manifold connecting to the intake boot.

Try removing it and cleaning it with a carb cleaner or something. If that doesn't work, it may very well need replacement.

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sp0rky · 08-07-2005, 01:17 PM

Since its a 90' theres no MAF, its an AFM.
DIfference is - it has the little flap that the air has to blow through and it is highly restrictive.

It CAN get out of tune and cause a BAD idle, but it wont cause the problem that leetman speaks of. I am 99% sure it is either the ICV or ICM.

MEDSTUDENT87 · 10-18-2007, 08:44 PM

I know this thread is old but I am having an interment problem as described above. I have recently replaced the intake boot due to severe cracking. Does anyone have a picture of where the Idle control valve is? My BMW is a 1990 525 also. Does it connect to the boot near the air filter side? If so should I spray card cleaner up the hose? Just figured I would try cleaning it or would that hurt the problem? If it is the ICV I am "seeing" it had some oil in the tube would that cause it to malfunction? Sorry for being confusing with my questions. Thanx for any info.

d3ity · 10-18-2007, 10:48 PM

Ok, I had this same problem....

For about a week.

Then I noticed the cause. Dude, it sounds dumb.... really dumb. and you're probably going to hit yourself in the head repeatedly if this is the cause, but this is what did it for me.

Check your drivers side floor mat. BMW floor mats are heavy enough to ride up on the bottom of your gas pedal... and if they're not anchored with those little clips... it's possible that's whats going on.

MEDSTUDENT87 · 10-19-2007, 03:21 PM

No the idle is funny sometimes and will drop around 500 instead of 700ish and the gas pedal would make it rise and my mats are anchored on those platic thingies.Thanx for the idea though.

benzin · 10-20-2007, 02:47 AM

Most likely the ICV,Clean or replace.As sporky said,I agree!

MEDSTUDENT87 · 10-20-2007, 09:44 AM

I think the ICV is the problem but no one has picutres of where its located and how exactly to clean it. I am sure it super easy and right in front of my face just cannot locate and wondering if someone had a pic of it in the engine bay and describe how to clean it thanx!

benzin · 10-22-2007, 08:12 PM

Well its not that easy.You should most likely remove the throttle body and clean it.As crap (ie.. carbon) and other stuff build up,The space between the throttle plate is obstructed.That causes less air to pass through.This makes the IAC motor try to compensate.Ruff idle and searching idle.Remove and clean with carb cleaner.Then hit the ICV.This will result in a very noticable difference.Let me know if it works.If any of you know a better way allso let me know.the more input the better.

saltshaker185 · 10-22-2007, 08:53 PM

the cleaning should be very similar to this... United Bimmer - BMW Enthusiast Community and Forums : Bimmer Technical Help if your engine is the m50 then it is even the exact same engine... look for a hose leaving the intake tube and it should lead to the icv then back into the intake manifold...

heres another engine to compare yours to... Idle Control Valve Write up; ICV clean DIY - Bimmerforums - The Ultimate BMW Forum