ICVs- who has a new one? Time to show&tell or more accurately... pull&blow!

[genphreak]

Hi all,

OK we know the ICV is a major cuplrit for poor idle and economy. And those in the know say it is easily testable; (ie working or not) by measuring the resistance of the internal windings with a multimeter (checking pins 1-3 in the connector should read 40 ohms and pins 1-2 & 2-3 about 20 ohms).

But; when the ICV is in the closed position, surely it should physically seal properly?

I just pulled mine to check it- it is still nice and clean and the resistance values are ok, and it snaps into position fine when 12V is applied to either pin 1 or 3 (keeping common on pin 2), but in the closed position one can still suck/blow (hmmm which is the best method (must make a note to ask my gf- as she will probably say 'F@#k off') a small amount of air through the valve.

Surely on a new ICV a perfect seal is made when closed? Could this the reason why my economy is a tad suspect?

Has anyone got a new ICV that can try this great test (ie pull and blow) can tell us if it seals perfectly when closed?

If so, this could well just help all the other members who are wondering why their fuel economy is not quite right... despite everything tried so far.

Beside, the test is a lot of fun peeps... ;) Nick

[BillionPa]

well, the engine is pulling more air through the throttle when the ICV is closed, and that air is metered, so it should not effect performance or economy.

[Morgenster]

I don't think that an ICV not sealing properly would increase consumption.
don't the MAF and O2 sensor take care of that?

[BigKriss]

Have you replaced the breather hose? 11 15 1 276 485? (http://realoem.com/bmw/showparts.do?model=HD12&mospid=47382&btnr=13_0167&hg=13&fg=15&hl=58)

I replaced this about 2 weeks ago, there is a little hole that is almost closed on the new item and maybe 2mm on the old item. The hole accepts a hose to somwhere on the intake manifold I assume?. Idle is a lot better now, around 700 rpms with little fluctuations.

[genphreak]

well, the engine is pulling more air through the throttle when the ICV is closed, and that air is metered, so it should not effect performance or economy.City consumption is 16.5L/100 driving smoothly but promptly. Never hard on the gas and never that fast pulling away. City is a hard figure to compare, but on the freeway I get 11.5L/100 averaging 110kmh on cruise. I believe this is at least 10%, if not 20% high for a good motor. It should get 9.5L I would hope, though I have never seen the official figures- does anyone know what BMW quote?

11.5L/100km = 20.5 miles to a US gallon (24.6 UK gallon)

I believe others get 24 miles to the gallon in the US on the highway, which is the equivalent of exactly 10.0L/100km.

However I feel that around town its using a lot more than it should: The OBC reckons 16.5-16.9L/100km (13.9-14.3 miles/US gallon).

Billion PA, thanks for making me think! When the ICV closes, air is bypassing the throttle body, and I expect (as it is ALL metered air), the ECU should not be miscalculating mixture at all. On an M30 the ECU only knows about 2 throttle conditions; Closed, Open (however much), and all the ICV does is act like a mini throttle device to balance the engine at idle. Of course, in order to do this, it must be able to open and close smoothly and not grab at any stage along the way, otherwise air cannot be adjusted fast enough to keep idle stable (let alone suffer the resultant little lean/rich conditions), so I've checked this out on my ICV and she opens really smooth; in fact she only needs 3V to open and close (though with 12V it really moves fast).

But if the ICV leaks, one will be holding the throttle open a little less to achieve the same engine power. Following the thinking above, the only thing this would affect would be the transmission as it has a cable linked to the throttle. This could lead to delayed gear changes, though I don't know if it would be enough affect economy much. But it might be enough to affect it a bit... but 10%... hmm...

If I really blow hard I get some air through the valve (even if applying 12V to hold it absolutely shut). Since an M30 can suck enough air at idle to suck your arm through the throttle body, I think it might be able to work the ICV a fair bit harder than me- it would be a bit.

But then again, I don't see how an ICV can seal flow exactly- unless it has little rubber seal in there. Perhaps this is why Whit says never to use carby cleaner on ICVs- but I would need to cut the little sucker open to see :(

[genphreak]

Have you replaced the breather (vent) hose? 11 15 1 276 485? (http://realoem.com/bmw/showparts.do?model=HD12&mospid=47382&btnr=13_0167&hg=13&fg=15&hl=58)

I replaced this about 2 weeks ago, there is a little hole that is almost closed on the new item and maybe 2mm on the old item. The hole accepts a hose to somwhere on the intake manifold I assume?. Idle is a lot better now, around 700 rpms with little fluctuations.Hey buddy, glad to hear that. Yes I changed the vent hose too, (all the rubber hoses in fact), but the OE replacement of that particular hose seems as bad as the stock one. The breather hose that comes out of the plug on the side of it goes to the manifold- the one opposite the hose that runs the FPR. I expect this is to prevent too much vacuum pressure being applied to the crankcase when the throttle goes wide open, but to these layman's eyes it really seems like an afterthought in comparison to the rest of the system.

I wonder if anyone would know the story behind that little sucker...

There is only one other hose apart from the brake booster hose and that is the charcoal cannister hose to a bigger port further up under the intake.

I've changed every hose, evcery valve. Replaced even the throttle body-AFM boot, checked every connection- there has to be a leak somewhere! :) Nick I need an exhaust gas analyser, bad... I'll use some propane tomorrow- maybe that will isolate it...

[Javier]

figures according to the owners manual (I personally feel it is a joke).

Manual (http://luuk.xs4all.nl/bmwboeken/bmwe34manual/html/pg97.jpg.html)

Javier

[genphreak]

figures according to the owners manual (I personally feel it is a joke).

Manual (http://luuk.xs4all.nl/bmwboeken/bmwe34manual/html/pg97.jpg.html)

JavierThank you Javier.

In that BMW claims 9.6L highway, 17.4 city for my car M30B35 auto+cat.

Describes my car for city cycle and but puts me 15% high for highway cycle. My city driving however is probably more long distance-ish, not metro traffic all the time, so it could well work out to be 15% high on that too.

Re you concern about accuracy of the figures- perhaps the mileage it claims is in UK gallons... (EDIT second look- yes, it states Imperial Gallons). There's a good converter here (http://www.projects.ex.ac.uk/trol/scol/ccfuel.htm).

I'll have to check my tranny cable/TPS/AFM for stock settings as per the TIS tommorrow.

Wish I knew if the ICV should seal properly when closed though.