Idle Air Control Valve Question

E28 technical advice asked and given! Troubleshooting, modifications and more.
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cosmosblau
Posts: 16
Joined: Nov 15, 2021 1:48 AM
Location: Sydney & Los Angeles

Idle Air Control Valve Question

Post by cosmosblau »

I have a surging idle problem... Happens randomly and can occur hot, cold, parked and while driving. I've seen plenty of threads on here for this issues and my mechanic has recently told me he's quite sure it's the IACV.

Now, I was looking into replacements and I was always under the impression that I would just look for a used Bosch replacement... However, I went and gave it another look and it appears to be a VDO L-Shape Idle Regulating Valve (Part Number: 13411709898).

These things seem pretty rare and I felt like these were only used on M10 engines... I have an 87 525e (Australian Model).

Any suggestions for replacements? I still figure I might take it off and give it a clean with some carb / throttle body cleaner to first see if that does the trick.

But hey, thought I'd as you guys. I know it's probably a fairly tired question but with all of the threads and issues other owners have had, it feels like it could be a wormhole that can make me feel like my car has 100 other issues.

Thanks!
Aldo525
Posts: 276
Joined: Mar 24, 2021 3:04 PM
Location: CHILE

Re: Idle Air Control Valve Question

Post by Aldo525 »

Hello,

If your car is up to 12/86 (check the VIN at Realoem) the IACV is 13411709898 (VDO), but as you mention 87' 525e the right IACV is 13411286065 (BOSCH) and they are not the same, not even the plug. Look the pictures:

13411709898 (VDO): this have three "pipes", so three hoses.
Image

13411286065 (BOSCH): this unit is two pipes, so two hoses
Image

Plus different plugs....check what is the right IACV for your car, they are not interchangeables.
Mike W.
Posts: 26872
Joined: Feb 12, 2006 12:00 PM
Location: California Whine Country

Re: Idle Air Control Valve Question

Post by Mike W. »

That seems to be the standard one for 525e/528e cars. Not as bad as the ones that came on our 533 cars, but still, a bit cranky. One problem is often the control unit also needs to be replaced. Looking a bit they seem to be out of production so your choices are a hyperexpensive new old stock, or a used one.

A possible option might be (now I think this is the correct part number, but I'm not sure) 11631271342 which is labeled as a "bypass housing" but I think is the manual idle control on 525i/528i E28s. Not as neat as auto electronic control, but since it's just a housing with a screw to adjust volume it's pretty reliable.

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cosmosblau
Posts: 16
Joined: Nov 15, 2021 1:48 AM
Location: Sydney & Los Angeles

Re: Idle Air Control Valve Question

Post by cosmosblau »

Checked my VIN and it's actually a 07/86 model. Pretty odd as it comes up as an 87 when I do my registration... But yes, I can confirm visually as well that it's the VDO model.

Not a lot of them out there. That's for sure.

I'll take on the feedback about the other options available and assessing the control unit in the future, but do you guys reckon it's worth giving it a clean first to see if that solves it? Obviously the cheapest option.
Mike W.
Posts: 26872
Joined: Feb 12, 2006 12:00 PM
Location: California Whine Country

Re: Idle Air Control Valve Question

Post by Mike W. »

Oh sure, you might as well clean it and try, I mean the price is right and you don't have much to lose. Just don't have high expectations.
RetiredDoc
Posts: 1316
Joined: Feb 12, 2006 12:00 PM
Location: Aiken SC

Re: Idle Air Control Valve Question

Post by RetiredDoc »

I am guilty of taking a half dozen VDO ICV’s off the market. Back in my earlier e28 days when we still had a U-pull junkyard nearby I pulled a couple for spares, and and bought a few more on ebay as parts of boxes of misc BMW parts being auctioned. Recently developed the hunting idle problem, and tested them all with my multimeter. All tested good, but after swapping in two with no improvement in running , it turned out that my problem was the ICC.

Have you tested your iCV as bad or just think it may be the problem?
cosmosblau
Posts: 16
Joined: Nov 15, 2021 1:48 AM
Location: Sydney & Los Angeles

Re: Idle Air Control Valve Question

Post by cosmosblau »

Classic! I've extensively scoured the web and I reckon there are about a dozen new VDO units left in the world.

I still haven't had the time to clean the ICV, but I think to your point it could be worth investing in a cheap multimeter to actually know if it's an issue with that part. I could end up spending a lot more time and effort when it's just the Idle Control Module (I'm guessing this is what you're referring to when you mentioned ICC).

But, I'll probably still try to source one of those VDO ICVs just to plan ahead and avoid potential pain in the future.

Will report back soon with results. Thanks again.
Aldo525
Posts: 276
Joined: Mar 24, 2021 3:04 PM
Location: CHILE

Re: Idle Air Control Valve Question

Post by Aldo525 »

cosmosblau wrote: May 22, 2023 12:43 AM Classic! I've extensively scoured the web and I reckon there are about a dozen new VDO units left in the world.

I still haven't had the time to clean the ICV, but I think to your point it could be worth investing in a cheap multimeter to actually know if it's an issue with that part. I could end up spending a lot more time and effort when it's just the Idle Control Module (I'm guessing this is what you're referring to when you mentioned ICC).

But, I'll probably still try to source one of those VDO ICVs just to plan ahead and avoid potential pain in the future.

Will report back soon with results. Thanks again.
My experience with ICV in 525i e34 Motronic (Guess 525e e28 is Motronic too) was (after checking the original unit in all parameters, resistance, volts, etc, that showing a Good unit) a continuos failure (rough idle when cold and warm) until I bought the ultra very high expensive original Bosch unit....that was the erratic idle solution. Before that, first tried a cheap chinese ICV....very bad option, second a Löwe unit (from Germany) which works ok when cold, but high revs when warm.....

Seems to me a new Original ICV are the real solution....an original used one maybe not (even if the unit is "ok")
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