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Hunting for idle even when ICV tests as good

E28 technical advice asked and given! Troubleshooting, modifications and more.
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blockerb
Posts: 146
Joined: Apr 28, 2011 9:58 AM

Hunting for idle even when ICV tests as good

Post by blockerb »

interesting situation here. stock 1986 528e.

Car runs quite well with the current iCV and no hunting for idle. I purchased another iCV on ebay for a backup. here's the outcome

1.  car idles and runs fine with current ICV
2. Replace with ebay ICV and car started fine. Once it started getting to temp, it began hunting for idle.  pulsing form ~1000RPM to ~2000RPM and back down....back up and so on.
3.  reinstall current ICV and runs and idles fine.
4.  Test ebay ICV with a 12V tester and plunger in the ICV is activated and closes like clockwork when voltage is supplied.  

not sure what this means or where to go next.
turbodan
Posts: 9246
Joined: Jan 09, 2007 10:19 PM

Re: Hunting for idle even when ICV tests as good

Post by turbodan »

The ebay ICV may have a temperature related electrical issue. You are fortunate to have a known good ICV to test it against. 

All I can think of is to check the adjustment screw on the troublesome valve. See if you can get it working properly with the screw turned further in or out. There's not much else that can be done with them.
4DSC
Posts: 134
Joined: Sep 21, 2012 1:53 PM
Location: Atlanta, GA

Re: Hunting for idle even when ICV tests as good

Post by 4DSC »

I've had an ICV show a vacuum leak where the electric connection plug is on the body during a smoke test, but I doubt that would cause that erratic of an idle condition.
Mike W.
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Location: California Whine Country

Re: Hunting for idle even when ICV tests as good

Post by Mike W. »

While not an expert on this system, to me, if one tests good and the other doesn't, that means it's bad. Might be repairable, might not, might just be sticky or something, but you have verified that the system works. But not with the ebay valve. Easy call from here that it's bad, even if it bench tests good electrically. Bench testing, while a good test, is not the same as on the car.
Chimi-Changa
Posts: 1666
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Location: Massachusetts

Re: Hunting for idle even when ICV tests as good

Post by Chimi-Changa »

"Another ICV" being an original part used? Or new (built in Asia?) part?  A known working used one might be the best bet.
blockerb
Posts: 146
Joined: Apr 28, 2011 9:58 AM

Re: Hunting for idle even when ICV tests as good

Post by blockerb »

Chimi-Changa wrote: Jan 23, 2025 7:30 PM "Another ICV" being an original part used? Or new (built in Asia?) part?  A known working used one might be the best bet.
The Ebay one was a used OEM ICV.  I don't of anywhere you can get a new non-OEM one that works (Asia, China,etc.)
Aldo525
Posts: 396
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Location: Puerto Varas, CHILE

Re: Hunting for idle even when ICV tests as good

Post by Aldo525 »

blockerb wrote: Jan 24, 2025 9:44 AM
Chimi-Changa wrote: Jan 23, 2025 7:30 PM "Another ICV" being an original part used? Or new (built in Asia?) part?  A known working used one might be the best bet.
The Ebay one was a used OEM ICV.  I don't of anywhere you can get a new non-OEM one that works (Asia, China,etc.)
Based on my experience, just the Bosch OEM is the ICV solution. I know is hard to find and very expensive, but previously I tried chinese version (very bad, uncontroled idle) and from Germany a Löwe ICV (good idle when cold but high rpm when warm). Finally spend a lot of money in a OE Bosch made in Germany and problem solved. Both chinese and Löwe was purchased at eBay.
blockerb
Posts: 146
Joined: Apr 28, 2011 9:58 AM

Re: Hunting for idle even when ICV tests as good

Post by blockerb »

Aldo525 wrote: Jan 25, 2025 6:56 AM
blockerb wrote: Jan 24, 2025 9:44 AM
The Ebay one was a used OEM ICV.  I don't of anywhere you can get a new non-OEM one that works (Asia, China,etc.)
Based on my experience, just the Bosch OEM is the ICV solution. I know is hard to find and very expensive, but previously I tried chinese version (very bad, uncontroled idle) and from Germany a Löwe ICV (good idle when cold but high rpm when warm). Finally spend a lot of money in a OE Bosch made in Germany and problem solved. Both chinese and Löwe was purchased at eBay.
interesting. Where did you get the Bosch version and part number?
Aldo525
Posts: 396
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Location: Puerto Varas, CHILE

Re: Hunting for idle even when ICV tests as good

Post by Aldo525 »

blockerb wrote: Jan 26, 2025 9:44 AM
Aldo525 wrote: Jan 25, 2025 6:56 AM
Based on my experience, just the Bosch OEM is the ICV solution. I know is hard to find and very expensive, but previously I tried chinese version (very bad, uncontroled idle) and from Germany a Löwe ICV (good idle when cold but high rpm when warm). Finally spend a lot of money in a OE Bosch made in Germany and problem solved. Both chinese and Löwe was purchased at eBay.
interesting. Where did you get the Bosch version and part number?
 
 
According RealOem, there are two ICV's for an 86' 528e and this is maybe the reason why your second ICV doesn't work:

1) OE  13411709898 (VDO 408.202/009/002)
2) OE  13411707395 (VDO 408.202/009/001)....this one only applies when the car have a Idling Control Unit 13411286133. This unit is located next to the ECU in the glovebox, so first check if your car have or not that Control Unit to select the right ICV.
Mike W.
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Re: Hunting for idle even when ICV tests as good

Post by Mike W. »

Aldo525 wrote: Jan 26, 2025 1:59 PM
1) OE  13411709898 (VDO 408.202/009/002)
2) OE  13411707395 (VDO 408.202/009/001)....this one only applies when the car have a Idling Control Unit 13411286133. This unit is located next to the ECU in the glovebox, so first check if your car have or not that Control Unit to select the right ICV.[/justify]
Interesting, while not a student of eta's, I thought they were all the same until the super e which used the same type as 535's. Looking at Realoem it gets even more confusing.

It doesn't paste well so I'll just throw a link out, but it seems like there might be more than one control unit, but it also looks like it doesn't matter. Head hurt. And that's not even counting early, pre 3-83 cars which it suggests use a still different one, although I didn't really dig in that deep to check the P/N's

https://www.realoem.com/bmw/enUS/showpa ... 3411286012
Foonfer
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Re: Hunting for idle even when ICV tests as good

Post by Foonfer »

Check #13 and #16 in this diagram:  https://realoem.com/bmw/enUS/showparts? ... Id=11_3635

Coolant Temperature Sensor 13621357414
Temperature-Time Switch 13621362599

If idle is OK at some temperatures but bad at others, these sensors might be coming into play.  They're not expensive, they are a 5-minute fix, and doesn't hurt to try.
Mike W.
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Location: California Whine Country

Re: Hunting for idle even when ICV tests as good

Post by Mike W. »

Foonfer wrote: Jan 27, 2025 11:09 AM Check #13 and #16 in this diagram:  https://realoem.com/bmw/enUS/showparts? ... Id=11_3635

Coolant Temperature Sensor 13621357414
Temperature-Time Switch 13621362599

If idle is OK at some temperatures but bad at others, these sensors might be coming into play.  They're not expensive, they are a 5-minute fix, and doesn't hurt to try.
Thermo time is a switch not a sensor and only comes into play while cranking so it should not be an issue at all.
Foonfer
Posts: 747
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Re: Hunting for idle even when ICV tests as good

Post by Foonfer »

Mike W." wrote: Jan 27, 2025 12:31 PM
Foonfer wrote: Jan 27, 2025 11:09 AM Check #13 and #16 in this diagram:  https://realoem.com/bmw/enUS/showparts? ... Id=11_3635

Coolant Temperature Sensor 13621357414
Temperature-Time Switch 13621362599

If idle is OK at some temperatures but bad at others, these sensors might be coming into play.  They're not expensive, they are a 5-minute fix, and doesn't hurt to try.
Thermo time is a switch not a sensor and only comes into play while cranking so it should not be an issue at all.
 
 
 
 
I would follow Mike's advice - I am not familiar with pre-1988 Etas or with the Thermo-time switch.
My car, which now has a M30B35, has two similar devices (older M30s I think have three) - One is the "coolant temperature sensor" and the other is the "coolant temperature sender" (which "sends" information to the engine thermometer in the cluster).  When my car had idle issues, I swapped the sensor and it made a significant difference (this after having swapped other usual suspects such as the ICV).

Oh another tip:  These are cars with 40-year old rubber parts.  Elbows, boots, hoses, etc can and will develop cracks.  Idle is very dependent on a good vacuum, and cracks result in air leaks which result in more difficulty to keep a good idle.  The ICV in our cars connects to the adjacent hoses via "pagoda"-type toothed pressure connectors.  If you can, it wouldn't hurt to secure these connections with hose clamps of adequate size. 
Aldo525
Posts: 396
Joined: Mar 24, 2021 3:04 PM
Location: Puerto Varas, CHILE

Re: Hunting for idle even when ICV tests as good

Post by Aldo525 »

I believe here we have a misunderstanding....first post talk about a running good engine but when a new ICV purchased as a spare part is fitted in the car, the engine runs poorly....so the problem is the new (old used one) ICV
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