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jetape

Idle gets stuck higher sometimes

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This is pretty random but sometimes my idle will get stuck few hundred RPM higher than it should.  The only way to correct it is to shut down and start again.  It doesn't happen often but I've been noticing it lately.

I was logging today when it happened so have some data, the throttle looks to be open more than what the actual pedal position would request.  I'm not pressing the throttle here.

(keep in mind this is a jetski so no wheel speed available)

 

 

stuckidle1.PNG

stuckidle2.PNG

stuckidle3.PNG

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Do you have the log file or just those screen shots? There are a couple of closed loop ethrottle offset issues that have been reported that last few months that sound similar. Can you post the whole log - the value we're looking for is ethrottle ISC CL trim %

Are you on the latest firmware (released last week)?

If you leave it for say 10 seconds does it slowly return to normal?

 

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3 hours ago, cj said:

can you put it in dropbox/googledrive/megaupload/etc and link to it?

 

https://www.dropbox.com/s/7zu9ogjyr1xd3nc/aug18.llg?dl=0

It's a pretty weak log, the ones where I tried to get it unstuck longer I must have not saved.  This one I basically shut down few seconds after it happens to reset it.

11:34 - wrong idle; accelerator is not being pressed and registers 0.2 and throttle position reads 8.2

11:10 - proper idle; accelerator at 0.2 and throttle position 6.9

 

Idle is set at 1800 RPM

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Looking at your log a couple things jump out at me. 

1) there is a little bit of variance between your TPS main and TPS sub. not enough to cause the ECU to kill ethrottle control but enough to make low throttle openings a little off - eg at 11:34 there is 0.7% between them - doesnt mean much at 95% but at 7% thats 10% difference between them. try recalibrating your TPS. Your APS is also consistenly about 0.2 different between main and sub, probably doesnt make any difference with this small a number but worth a shot to recalibrate and see if it goes away.

2) you dont have any open loop idle numbers defined when at normal temperature so are leaning on closed loop quite heavily to get the idle right. As you have no doubt noticed you can only get the ethrottle target table to within 0.5 which isnt granular enough most of the time - the open loop table is ideal for (in your case) tweaking it slightly so the base idle number is the 7.2 your engine seems to like rather than 6.5 or 7 like you have to enter in the ethrottle table.

3) At 11:34 its right after you just blipped the throttle 3 or 4 times, which causes the CL trim to jump up by 0.4 every time you do it and its at +2.2% at 11:32 when you stop touching the throttle. (for comparison, your normal 1800 RPM idle has CL trim at +0.7%) Over the next 4 seconds the target TPS is reducing as its supposed to, and if you had left it another 10 seconds it probably would have returned to normal. (see picture below)

4) Lastly, your PID settings for ethrottle control are a tiny bit off which is making your low throttle angle changes a bit jumpy and registering the odd TPS tracking error - eg at 11:33 the target drops from 8.5 to 7.8 over about half a second but the TP angle bascially doesnt change. This might be just an artifact of point 1 above because the TPS sub signal is nearly a point off and i'm not sure if it averages them or just uses main when they are like this. Fix the other points before tweaking this but it might need fixing after all.

image.png.107cd245a6c5b02f08bfedebeebd169d.png

At 11:34 in that log, your idle is about 2200. You mentioned that you have seen it "worse". In this worse case, was it stuck at the same RPM or was it a bunch higher - specifically was it over 2400 rpm? 

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7 hours ago, cj said:

At 11:34 in that log, your idle is about 2200. You mentioned that you have seen it "worse". In this worse case, was it stuck at the same RPM or was it a bunch higher - specifically was it over 2400 rpm? 

 

Yeah sometimes it gets stuck around 2700, I bumped the ignition control lockout to 2500. 

When I was setting up the ethrottle PID I had the throttle disconnected and was looking a the blade movements.  Thought I got it as close as I could without bouncing and flattering.

I need to read up a little on open loop idle, I was planning on turning off closed loop this weekend to play with it.

 

Thanks for the feedback :)

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5 hours ago, Ducie54 said:

Have you looked at dropping the ignition values in the cells just above idle on decell, and being more aggressive with the idle ignition table.  

I used to have more aggressive ignition idle table where it went down as low as 5 degrees but that created an issue where if the jetski got some air and throttle was released it would overshoot on the downside to the point where engine was close to stalling when ski landed and load on the jet pump was regained.

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You have exactly the same issue as this post, right down to the 0.4% being added to the CL idle trim every time you blip the throttle.

I suspect when it gets stuck at 2700+ rpm you have the same issue this guy does where your RPM is above the lockout for CL idle to be active and reduce the idle correctly. In this other post it looks like idle ignition control might be an option as a workaround - not by setting it too aggressively, but by setting it gently but having the lockout threshold quite high so that ignition idle control can still drag your idle down when CL idle is above its lockout RPM and can no longer fix itself. Or you could just switch to open loop idle only which works fine.

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