# EMU Black V2 to V3 – difficult cold starts and Bosch 3-wire idle valve issues
**URL:** https://community.ecumaster.com/t/emu-black-v2-to-v3-difficult-cold-starts-and-bosch-3-wire-idle-valve-issues/6553
**Category:** V3 SOFTWARE
**Created:** [September 21, 2026, 8:39pm UTC](https://community.ecumaster.com/t/emu-black-v2-to-v3-difficult-cold-starts-and-bosch-3-wire-idle-valve-issues/6553 "2026-09-21T20:39:13Z")
**Posts on this page:** 10
**Page:** 1
### Author:  [@alex.cristocea](https://community.ecumaster.com/u/alex.cristocea)
#### Post date: [September 21, 2026, 8:39pm UTC](https://community.ecumaster.com/t/emu-black-v2-to-v3-difficult-cold-starts-and-bosch-3-wire-idle-valve-issues/6553/1 "2026-09-21T20:39:13Z")
Hi everyone, I’m looking for some help with my 1987 Porsche 944 Turbo, a 2.5-litre 4-cylinder running an EMU Black, currently on V3.061. On V2 the engine started well from cold and the idle valve worked properly, but since moving to V3, starting has become much more difficult and I’ve been struggling to get usable idle control. The valve is a Bosch 0 280 140 501, 3-wire PWM, with +12 V on the centre pin and the two control wires connected to G12 and G13. I’ve also refitted and cleaned the actual valve that previously worked well on V2, but the problem remains. During troubleshooting I found that the actuator type was set to stepper in V3 and corrected it to 3-wire PWM. The current settings are 120 Hz, output 1 AUX 2/G13, output 2 AUX 5/G12, invert output off, and minimum/maximum duty limits of 10% and 90%. Cranking airflow is currently 45% across the temperature range. I don’t have a verified side-by-side comparison of every V2 and V3 setting yet, so I can’t claim that all the numerical settings are identical, but this valve did work properly on V2. In earlier cold tests using the idle override, there was very little response below about 54%, then around 55–56% the engine would jump to roughly 1,700 rpm and sometimes keep climbing. Reducing the command back to 53–54% did not immediately bring the speed down; I had to go down to roughly 30–40%, or switch the override off, to get back to around 500–600 rpm. With the cleaned, previously working valve fitted, I later tried adjusting the Active Airflow table. Around 60% brought the engine to approximately 1,700–2,000 rpm, and decreasing the value in 0.5% steps then gave a smoother reduction of roughly 50–100 rpm per step, down into the low-40% range. Those tests were under different conditions, so they aren’t a direct comparison. At present, both the airflow PID and idle ignition PID gains are set to zero while I try to establish a repeatable base setting. Starting is another issue: some cold starts take 5–10 seconds of cranking, and on some attempts the engine catches but dies after a few seconds. I’ve adjusted Cranking Fuel and increased it further between attempts without a clear improvement. One of the restart logs begins at CLT 44°C and IAT 37°C, so that particular test is only partially warm, not a true cold start. Battery voltage and fuel pressure have been checked, and the logs include injector pulse width, effective fuel pressure, trigger sync, lambda validity and idle command. I’m not convinced the starting problem is only an airflow issue, but I haven’t isolated the cause yet. Has anyone experienced similar behaviour with a Bosch 3-wire valve after moving from V2 to V3? Are there differences in the cranking fuel calculation, idle airflow command or 3-wire PWM operation that need particular attention when migrating? I can share the V3 XML project, CSV logs and screenshots of the settings. Any pointers on what to compare or test next would be appreciated.
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### Author:  [@baxtercrafter](https://community.ecumaster.com/u/baxtercrafter)
#### Post date: [September 22, 2026, 6:33am UTC](https://community.ecumaster.com/t/emu-black-v2-to-v3-difficult-cold-starts-and-bosch-3-wire-idle-valve-issues/6553/2 "2026-09-22T06:33:49Z")
AUX 1 and 2 have no flyback diode, use Aux 3-6
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### Author:  [@alex.cristocea](https://community.ecumaster.com/u/alex.cristocea)
#### Post date: [September 22, 2026, 8:38am UTC](https://community.ecumaster.com/t/emu-black-v2-to-v3-difficult-cold-starts-and-bosch-3-wire-idle-valve-issues/6553/3 "2026-09-22T08:38:57Z")
I installed with flyback diodes when I did the harness as the manual specifies. And withe the V2 version idle worked just fine that is what I dont understand
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### Author:  [@Jadzwin\_ECUMASTER](https://community.ecumaster.com/u/Jadzwin_ECUMASTER)
#### Post date: [September 22, 2026, 11:23am UTC](https://community.ecumaster.com/t/emu-black-v2-to-v3-difficult-cold-starts-and-bosch-3-wire-idle-valve-issues/6553/4 "2026-09-22T11:23:43Z")
What was your selected type of idle valve in V2 ? 3 wire pwm or 3 wire pwm no spring ?
Could you post your v2 and v3 idle solenoid settings ? I will check if the behaviour is the same.
The override DC is the best test as you should get smooth RPM control.
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### Author:  [@alex.cristocea](https://community.ecumaster.com/u/alex.cristocea)
#### Post date: [September 22, 2026, 6:20pm UTC](https://community.ecumaster.com/t/emu-black-v2-to-v3-difficult-cold-starts-and-bosch-3-wire-idle-valve-issues/6553/5 "2026-09-22T18:20:09Z")
Sure: V2 Idle settings:
The V3 (3.061)
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### Author:  [@alex.cristocea](https://community.ecumaster.com/u/alex.cristocea)
#### Post date: [September 22, 2026, 6:22pm UTC](https://community.ecumaster.com/t/emu-black-v2-to-v3-difficult-cold-starts-and-bosch-3-wire-idle-valve-issues/6553/6 "2026-09-22T18:22:41Z")
[idle override new isv.emublog3](https://community.ecumaster.com/uploads/short-url/aZXqIopq3hvaSGMbXZoiG3kNg5B.emublog3) (479.3 KB)
also this a test I did last week and you can see the behaviour of the isv valve
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### Author:  [@alex.cristocea](https://community.ecumaster.com/u/alex.cristocea)
#### Post date: [September 22, 2026, 6:31pm UTC](https://community.ecumaster.com/t/emu-black-v2-to-v3-difficult-cold-starts-and-bosch-3-wire-idle-valve-issues/6553/7 "2026-09-22T18:31:58Z")
There is a difference between actuator type v2 to v3. On V2 is - 3 wire PWM no spring, on V3 is 3 wire PWM. I dissasembled one idle valve and I can confirm that it has no spring. May this be the problem?
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### Author:  [@Jadzwin\_ECUMASTER](https://community.ecumaster.com/u/Jadzwin_ECUMASTER)
#### Post date: [September 22, 2026, 10:11pm UTC](https://community.ecumaster.com/t/emu-black-v2-to-v3-difficult-cold-starts-and-bosch-3-wire-idle-valve-issues/6553/8 "2026-09-22T22:11:04Z")
That is the reason No spring is different type of control. I will add this option to the next build.
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### Author:  [@alex.cristocea](https://community.ecumaster.com/u/alex.cristocea)
#### Post date: [September 25, 2026, 12:31am UTC](https://community.ecumaster.com/t/emu-black-v2-to-v3-difficult-cold-starts-and-bosch-3-wire-idle-valve-issues/6553/9 "2026-09-25T00:31:15Z")
Ok, thank you! Looking forward for the new release.
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### Author:  [@Muhraka](https://community.ecumaster.com/u/Muhraka)
#### Post date: [September 26, 2026, 12:19pm UTC](https://community.ecumaster.com/t/emu-black-v2-to-v3-difficult-cold-starts-and-bosch-3-wire-idle-valve-issues/6553/10 "2026-09-26T12:19:53Z")
Hi, any idea when the new build will be available? I am also having the same problem with Renault 21 Turbo 3 wire idle valve.