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High initial startup RPM

Posted: 2023 May 24, 23:50
by 88gthatchback
I cant figure out what is causing a high idle immediately after startup. It lasts 5-10 seconds and revs to 2000RPM then settles into a nice RPM. I have lowered FN1861 considerably but it doesn't seem to effect the 0-5 seconds after startup. Temperature doesn't have an effect. Even when hot it still revs to 2000 for 5 seconds before settling into a normal RPM. What parameter is causing this? I am running the latest A9L2. I attached my BIN if anyone wants to take a look.

Re: High initial startup RPM

Posted: 2023 May 25, 13:39
by odrapnew
What is your DESRPM during that high rpm phase?

Re: High initial startup RPM

Posted: 2023 May 25, 20:33
by 88gthatchback
SPK_DSDRPM is showing 1328 but actual RPM is almost 1900. Here's a log of 2nd startup.

Re: High initial startup RPM

Posted: 2023 May 26, 13:34
by odrapnew
I'm not able to look at tuning files on this computer, so I can't see you bin or log file.

How much did you change FN1861 table?

I noticed when I started dialing in my startup idle, I had to make bigger changes than I thought (like increments of 0.5) to get noticeable changes in the colder temp columns (100F and below).
I've since been able to make smaller increments now that I'm close to ideal.

I've been dinking around with tuning for a while, but still consider myself a novice, however, even over the last month or so, I've learned a lot of what happens with idle and why and have made huge strides in making my car idle better and more consistently.

Re: High initial startup RPM

Posted: 2023 May 31, 19:46
by 88gthatchback
The ISCDTY is going to 100% immediately after startup and stays there for 5 seconds then starts to come done. There must be a table that I'm missing. Attached is a screenshot of FN1861 and the dashboard.

Re: High initial startup RPM

Posted: 2023 Jun 01, 12:17
by decipha
desmaf is adding 74% duty cycle

Re: High initial startup RPM

Posted: 2023 Jun 02, 09:00
by 88gthatchback
Where do I look to find out what's causing the desmaf to add 74%? I've read the writeups over and over and cant figure this one out.

Re: High initial startup RPM

Posted: 2023 Jun 02, 10:00
by decipha
dsdrpm is higher than actual N rpm so closed loop idle control is adding air to reach target idle

if its commanding that high of an rpm when warm started and still not hitting target then there are 2 most likely culprits
first its either too lean at startup and the engine is needing a ton of air. Go add 0.15 to the startup enrichment table for the first 15 seconds and see if it makes her happier.

and secondly for it to command that high of a duty cycle when hot starting either the throttle stop is too far out which you can verify but waiting til she gets to warm stable idle after shes been running at least 5 minutes over 200 degree coolant temp. If the iscdc is above 35% then the throttle stop needs to be opened up. Otherwise the idle air control valve is probably not working correctly either wiring or its weak / old or installed backwards.

Re: High initial startup RPM

Posted: 2023 Jun 04, 09:21
by 88gthatchback
I figured it out. I was adjusting the ISC multiplier the wrong way. It wanted more but I kept taking it out.