Howdy folks -- help me work on a puzzle, if you want. Every day, on the first start of the day, my high idle drops rapidly to 500-600 RPM immediately after it starts, and then recovers back to its normal fast idle progression. Later in the same day, it starts pretty much perfectly, or even if I immediately turn the car off and restart it it does well.

Thoughts? Also would love general tune critique from those more experienced than I.

Drives 95% good but has a couple hiccups, this issue, and my AE tuning isn't perfect. It stumbles the tiniest bit on the first throttle blip from idle, but then it cleans up if you romp on it for a bit. Adding fuel in the AE curve doesn't help, but it sure acts like it needs more fuel and is benefitting from wall-wetting.

1991 1.6L, Kraken high-mount GT2554R, converted to sequential with Bosch 700cc injectors, R8 COPs, open-loop boost controlled to 9-10psi.
Thanks for any input!

 

Its a shame your wideband takes ~40 seconds to warm up, it'd be really helpful to see that information during this high idle. Is there a way you can power it directly from the battery and take another log?

I see a few issues, like CL idle not activating until the RPM has fallen about half way from it's starting RPM to the dip you're experiencing, this is due to your CL idle activation waiting 2 seconds.

I believe it's due to a loss of fuel after cranking, if you look at PW, which is a summary of ALL fueling settings, it plumets from 8.8ms to 2.1, and your idle falls with it until it picks back up to 6ms, although stable idle happens at 2.0ms, it may be dropping off way too fast.

 

I don’t have an easy method of powering the wideband, unfortunately all that stuff is crammed into a nice tidy dash install. I do see that my CL idle takes a couple sec to kick in every time, but it looks to me like the IAC duty cycle stays plenty high during the open-loop part of the startup process, and I agree that insufficent fuel is likely the problem, and not air.

I don’t understand what part of the software could be telling it to back off in PW so quickly but I’ll go through my cranking enrichment settings and see if I can make better sense of them. Any tips you’ve got would be great

 

Try updating to the latest firmware, if you're not already, I've fixed a number of weird issues like this with a firm-up. You can also increase your after start enrichment taper time. Here's a photo from Link's help file that might help you visualize what you're trying to achieve with the settings MS has. Note that Link does it all in seconds, where as MS does it in cycles. MS3 can change to 0.1 seconds for after start taper time. You'll have to use logs to determine how many seconds these settings are staying active, since ~500 cycles takes a different amount of time at 1500rpm vs. 1000.