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VVT swap idle issue

 
Old 12-02-2018, 06:24 AM
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Default VVT swap idle issue

Any ideas on the following idle issue? Idle is almost always stuck at around 2500 rpms. The odd part though is if I keep my foot on the brake and let the clutch out slowing as the rpms fall the idle will stay at a more reasonable 1100 rpms. But if I blip the throttle again or come to another stop the idle will stay back at 2500 rpms. I at first thought it was a sticking TB but I wouldn't think the idle would be able to be lowered by using the clutch and brake only if this was the case. I can give more info about the car if needed, but some of the relevant basics are VVT engine, Junk2 TB, MSLabs MS3 basic ECU.
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Old 12-02-2018, 12:21 PM
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Tuning noob here so I can't help much. Probably something with your CL idle controls. Post your tune and a log or else no one will be able to help you

Definitely do some searching it's a common problem when you're learning to tune you should find some useful results.
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Old 12-02-2018, 01:35 PM
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Just another note. The car was tuned by a professional.
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Old 12-02-2018, 02:16 PM
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oh ok, so it must be perfect

more than likely your dashpot or initial value is too high, causing it to hang around 2500. And I'm guessing your CL idle activation RPM is around 1800 or 2000rpm. So it won't try to control it until you draw it down with the clutch below it's activation RPM.

Post your tune.
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Old 12-02-2018, 02:21 PM
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Totally agree, Curly. Let me try to post it sooner than later for sure. Much appreciated!
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Old 12-02-2018, 06:57 PM
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Thanks all in advance for giving this a peak! Much appreciated. Also if you happen to see any other potential issues let me know. I am going to start a separate post of my dyno result now as well.
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Old 12-02-2018, 07:51 PM
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Oh you're on warmup/open loop mode. What's the idle duty percentage at when you're having this issue?

A log would be really useful.
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Old 12-02-2018, 08:10 PM
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Do you want a log just of high idle for a few seconds or worth bogging it down with clutch as well? I've never done a log. Is that just an option in tuner studio?

The tuner felt it might be a iacv issue but was surprised if it was the iacv the clutch would fix it.
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Old 12-02-2018, 08:48 PM
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Make it high idle, wait 5 seconds, then bog it down with the clutch. Yes in TS you're going to click on "datalogging", "start", click save, and at that point it's recording. Once you're done, click "stop".
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Old 12-08-2018, 06:01 PM
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Log attached. Thanks!
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2018-12-08_15.04.20.msl (301.8 KB, 6 views)
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Old 12-08-2018, 06:54 PM
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Ok, so the log shows you going from ~2400rpm and 38.8% idle DC, to 1200rpm and 34.9%, it immediately switches to 34.9% at 2400rpm. The only reason I can see for this 3.9% DC change is your fan settings, which when on, adds 3.9% to your idle DC. My thought is that you're running warm when at 2400rpm, which activates the fan, adding 3.9%. When you drag the RPM down, it's able to cool off enough to disable the fan and the 3.9% adder, resulting in what you're experiencing.

My recommendation is to change the 3.9% adder to 0, and tune from there. I've often set the fan on/off temps to slightly below thermostat opening temp, so it will allow the engine to warm up, but then turn the fan on and never turn off. This is especially helpful with spal fans that draw the idle down substantially every time they kick on.
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Old 12-08-2018, 07:40 PM
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The idles was stuck at 2400 even when car was warming up and the fan wasn't on. Also I'm 99% sure I didn't see the fan on during the logging but could be wrong.
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Old 12-08-2018, 08:35 PM
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Ah i see, you hit the deactivation temperature, but it was never activated in the first place.

Try selecting the ignition cells you're idling in at and subtract 20 degrees, that is one major thing that changes, since below 1350rpm, you activate idle advance correction and go from 31 degrees to 6 degrees.

you can also try activating closed loop idle, then initial value, then selecting that table and changing it all to 30%, then going back to open loop. It may be using that table for a "closed" position.
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Old 12-09-2018, 05:48 AM
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Thanks for all of the ideas. I'll do my best to try these things after the holidays when I'll have some spare moments and will report back. Thanks again for all if the help.
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