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Old 12-06-2010, 10:28 PM   #1
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Default high idle does not recover

continued from here

https://www.miataturbo.net/showthrea...highlight=idle.

I figure I thread jacked enough

I paid much closer attention to what happens.

The car starts after a few cranks. The idle starts high for about 4s. This is the time I have the PID closed loop algorithm set to catch. The idle drops well below target and is exceptionally lean. The car tries to catch, the idle isolates about twice between too low and too high. On the second oscillation it goes to 2k rpm and hangs. it won't budge. I drive around and no matter what the car hangs at 2000 rpm when idling. If I change a parameter in TS that causes the ecu to flash, then the idle drops to normal. I honestly believe that something in the PID algorithm isn't written correctly and it can not recover from certain situations.

This has happened in the past, I thought he solution was to reduce the CLT based cranking PW. I think this is a mistake. I think I need to richen the CLT based pulse width so that the idle is not trying to recover from a lean situation (causes oscillation) Any insight into this problem would be appreciated. As soon as I figure this out, my idle situation will be perfect.
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Old 12-07-2010, 09:51 AM   #2
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It the CL idle indicator coming up? You're probably in PID lockout mode.
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Old 12-07-2010, 05:10 PM   #3
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I'll have to check. Does that mean I need to raise or lower the PID lockout setting if it indicator is coming on?
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Old 12-07-2010, 05:49 PM   #4
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You're locked out of PID so the indicator won't be lit.
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Old 12-07-2010, 06:01 PM   #5
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Ok, so how do unlock it so I can get into the PID alg.? My PID lockout detection is set to 100rpm/s and max decel load percent is 33. I( think I will be able to avoid the situation by making the CLT cranking PWM richer, but we will see. Any suggestions for fixing the PID lockout?
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Old 12-07-2010, 06:07 PM   #6
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90 and 25 here, I think your kpa setting is too high.
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Old 12-09-2010, 03:38 PM   #7
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I'm finally starting to get somewhere and it appears to be a combination of things. CLT cranking duty, warm-up enrichment, idle target. The other things were sorted thanks to the previous posts.

I want to follow up and explain a little about the above for others that may have the same issues. My car seems to be happy in a very narrow AFR window while cold. If it is outside this range the rpm starts to oscillate. This can cause the PID to lockout if the PID lockout settings are incorrect. The cranking PWM and the warm-up enrichment have to be adjusted so that when the idle falls after the start it settles in the AFR sweat spot. My car also doesn't seem to like certain rpm targets. Adjusting the target by 25 rpm sometimes fixed the problem.

In a nut shell I had to sit and adjust the warm-up enrichment and target idle until the AFR was in a range that I thought was acceptable and the car was happy sitting there.

If the cranking PWM is too lean, then the idle doesn't want to initially settle and will start to oscillate.

The time to PID and the dashpot adder can help to settle the rpm (versus dropping it to target) by allowing the car to run a little bit before it tries to implement the PID algorithm.
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Old 12-09-2010, 03:45 PM   #8
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you should watch your spark advance too...when this starts to move, your idle will go with it.
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