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Discussion Starter #1
Hi all.

I wonder if someone can tell me what state the ICV should be in when off the car. I have mine off chasing a running problem, and I can see right through it. The little valve inside that opens & closes is slack and about half way open. I can move it back and forth with my little digit against what feels like a weak spring. Is this normal? I thought when unpowered the valve would be either locked open or closed against the motor that drives it when the car's running.
 

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From the M5 training manual:
"Idle Control Valve
The S62 engine uses an idle control valve for idle stabilization. During idle conditions, the throttle valves are closed and all idle air passes through the idle valve. The valve on the S62 engine is the three wire ZWD 5 system. The valve has two windings that oppose each other. By varying the duty cycle applied to the windings, the valve can be progressively opened, closed or held steady to maintain the idle at a specified speed. The valve has a mechanical fail-safe opening (30%) which will allow the engine to idle in the event of a malfunction with the control of the valve. The idle control valve also serves as a fail-safe in the event of certain faults with the throttle control system (EDR). The MS S52 control module can progressively open the valve to allow limited operation of the engine."

So the DME sends varying signals to two competing coils to set the angular position. I guess that's why it only has a weak spring as the spring is not normally required to control the position. But it sounds like that weak spring has an important function - if DME control of the IACV is lost, it boings to the 30% open and allows limping home.

Also, from WDS:
"Idle speed control
The idle speed control valve is designed as a non-wearing two-winding rotary actuator. The rotary slide valve in the idle speed control valve may only be tested by way of activation via a tester or by shaking. Moving the rotary slide valve with the finger or with a tool such as a screwdriver is not permitted. This would mean that the rotary slide valve would no longer function correctly.
The idle speed control valve is now responsible for several tasks and is therefore an important component in the intake air tract of the engine.
Small air leaks which may occur, for example, at leaking gaiters/cylinders or in the event of a varying gap in the throttle valve can be compensated up to a certain extent by the idle speed control valve.
The idle speed control valve opens a little more during the engine coasting phase and closes just before reaching idle speed. This prevents a high intake pipe vacuum and blue smoke emission (oil vapour via valve stem seals).
During engine start, the idle speed control valve enables an opening cross section that is above that of idle speed. This ensures the engine starts more efficiently.
The idle speed control valve features an emergency operation opening gap which ensures certain emergency running functions in the event of power failure."

That "don't touch with a screwdriver or a finger" has to be bullshit. No one would design a part that fragile, right? I think they were just anal about the spring being damaged and the valve not failing in the 30% position.
 

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Discussion Starter #3
Thanks chap, just the info I was after.

For the record, I am trying to find the cause of a vibration when taking up the clutch from standstill. Applying extra throttle masks the issue, but I should be able to creep the car forward along a flat bit of ground without the car shaking the seats loose. All the obvious clutch-related bits have already been done, like clutch disc, plate, bearing, flywheel, slave cyl, fluid. I'll keep this up to date if I get anywhere.
 

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Wow, that sounds bad. So it shakes JUST while you are engaging the clutch or while you are crawling along in first gear with the clutch fully engaged (pedal up)?
 

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Sure sounds like a clutch/flywheel problem but since you have replaced all those parts, and since it happens as you are loading up the drivetrain, it could be something worn or loose in the drivetrain or drivetrain supports, like engine mounts, transmission mounts, giubo, diff mounts, etc.

You could get the car up on 4 axle stands with the diff supported up on a trolley jack and let the clutch out with the parking brake lightly applied to load the rear wheels with someone underneath looking for what moves around.
 

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Thanks, that would be why I've never seen it LOL
 

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Was planning to but haven't yet. I can't imagine the straights I'd get into trying to remove my injectors... :(

Got a quote off the chap though, and he seems reasonable with good comms.

Quote: - 'The price to clean the ICV will be an additional £15, so £122 all in.

(The 'all in' being the 8 injectors also)


 

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Thanks. Especially useful as I was debating an injector clean but the chap that used to do mine has since retired. Have you used that place before?
Hi saturnuranus ,, may I ask what was the solutions in your problem ,, I have the exact same thing that you have..

Thank you
 
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