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Old 08-02-2016, 10:02 PM   #1
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Default VVT sticking at startup - causing stall

Hey guys, I've been scratching my head with a stalling after start issue since I finished my swap 6 months ago. Car is a by-the-book 1.6->VVT swap on MS3, and is running well otherwise. I finally tracked down the culprit, but I have no idea why it's happening. Key on, VVT angle reads 275deg (my minimum angle setting). Once the engine starts, it sits at 135deg for a few seconds, then VVT duty spikes to 100% momentarily, VVT angle drops, and the engine stalls. Sometimes it will recover and not stall, but not always. Hot or cold doesn't seem to make much of a difference (I set VVT min CLT to 100F, and now it sits at 135deg until 100F, then does the same thing). I just set my first column to 0deg advance (1100 rpm) from the base map's 33deg; I've only tested one cold start with this change and it drooped but didn't stall, however it's done that before.

Anyone have any idea why the VVT angle is changing suddenly like this and stalling the engine? I've read every VVT thread I can find and my settings don't seem to be much different from everyone else (they're pretty much the DIY base map). I'm not sure where it's getting the 135deg reading from either, since that's way beyond the actual range of the system.

Attached datalogs: first one is a hot start and stall, second is the most recent cold start with 0 advance at 1100rpm.
Attached Files
File Type: msq vvt 8-2.msq (237.5 KB, 18 views)
File Type: msl hot stall.msl (1.03 MB, 15 views)
File Type: msl cold start droop - 0deg 1100rpm.msl (1.28 MB, 20 views)
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Old 08-03-2016, 10:10 AM   #2
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Try moving the minimum angle back a little. like to 270. My VVT would not work at default settings. Long story on how I found it. But basically was out of expected range. If you are on the edge it may be slapping with Duty cycle and unable to recover before killing the motor. Worth a try anyway.
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Old 08-03-2016, 06:15 PM   #3
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What are your min and max duty settings? Post an image of your settings if you can.
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Old 08-03-2016, 09:20 PM   #4
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Quote:
Originally Posted by Justaturbo95 View Post
Try moving the minimum angle back a little. like to 270. My VVT would not work at default settings. Long story on how I found it. But basically was out of expected range. If you are on the edge it may be slapping with Duty cycle and unable to recover before killing the motor. Worth a try anyway.
This worked! You, sir, are a hero. Did a cold start, angle was immediately recognized as 0deg, and duty was added smoothly and linearly once min CLT was reached. Many thanks.

Any chance you (or anyone) have ideas for my only other remaining issue? During warmup, it goes super lean under tip-in, so backing out of the garage it wants to stall, and getting back on the gas after a shift gives a long lean spike and hesitation. Idle AFRs are good, so I assume WUE is good (it has been autotuned). I increased cold AE from 120% to 200% but it didn't seem to do much. Of course, right now cold=80F CLT.

Quote:
Originally Posted by gjsmith66 View Post
What are your min and max duty settings? Post an image of your settings if you can.
min/max duty is at 20% and 70%. I was hesitant to adjust those since it seems to stay right around 40% most of the time. In test mode, it doesn't advance all until all at once slightly over 40%, then retards all at once slightly below 40%. Looking at some logs, it shows min 19% and max 59%. I suppose those could be the values to use? Maybe I should also decrease the min and see if it will go lower.
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