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1uzfe Cold start stalls


SingleTipTerry

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I am having a bit of a cold start issue since we are starting to get into winter where i am at. The colder it gets in the morning the worse my cold start has been. It was about 42 degrees Fahrenheit the other morning when i went to take the car to work and it was having a hell of a time catching it self from stalling out. Only way i can keep it alive is to give it alittle bit of throttle to keep it from stalling. Runs at about 7.5 afr on start up and want to stall out then goes a bit lean after i give it some throttle to clear it out, It will recover after alittle bit. Would like to know how i can fix it if possible, Im still learning the software a bit so this is a bit new to me. I will upload a log and my tune file down below. Thanks to this forum i have been able to clear up an assortment of problems so im hoping this will be an easy fix. I appreciate the help 

https://www.dropbox.com/scl/fi/253adcoduorvlv9y7qmkl/SC400-Current-tune-11-1-23.pclx?rlkey=0mziitzmykbcjemqj9to4zqdj&dl=0

https://www.dropbox.com/scl/fi/wt86ojcmpj6wd8vatrhu6/PC-Datalog-2023-10-31-1-16-02-pm-rough-cold-start.llgx?rlkey=6gu0remsh49ib23p6boiickxp&dl=0

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Would anybody have an idea? Having a hard start and Cant really move the car when its cold. The colder its been getting the worse its been. Having a bit of a hard time understanding how to clean it up. Again id appreciate any help, even if its just pointing me in the direction of what i need to do.

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It sounds like is has too much fuel during cold start to me.  Some suggested changes as a quick test to see if its heading in the right direction or not.  

Also, you dont have ecu hold power set up, so make sure after turning on the ignition you wait a few seconds for the idle valve to re-home before cranking. 

  1. Multiply the whole pre-crank prime table by 0.5 (so the values are approx half of what they are now.
  2. Change the accel fuel to the example below. 

ep6E5o5.png

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So after changing the settings you recommended it still seems a bit rich. It stalled out again just like it did before. Its seems super rich for the first 20-30 seconds then It starts to move around a bit before it starts to chill out. Does not like when i touch the throttle for alittle bit til it warms up. Here is the log i just took

https://www.dropbox.com/scl/fi/vlufv5z36clo1hwpf51sm/PC-Datalog-2023-11-7-3-00-12-pm-Cold-start-adjustments.llgx?rlkey=bcrvbk6s5u5o3k36ar1kawzfm&dl=0

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  • 2 weeks later...

so i guess i wasnt letting the wideband warm up enough before firing the car up, Heres new log after letting the wideband warm up properly then firing it up. You can see when it hits the post-start enrichment it goes full lean for alittle bit before recovering and coming down to a reasonable afr when it starts to idle properly. Thank you for your help.

https://www.dropbox.com/scl/fi/f39ffm7b1uxv3379knc8x/PC-Datalog-2023-11-19-3-48-32-pm-hard-cold-start.llgx?rlkey=hh3288qxky1cq3fgdsx26bj9q&dl=0

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When it starts to die its right at the end of the crank enrichment cycle and leads into the post start enrichment, Stays at 17.1-17.2 afr for about 6 seconds and recovers. Ill mess around with the enrichment table a bit more tomorrow to see if i can get it to react the right way but so far i havent been able to clear up the low idle lean condition when it first fires up.

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I dont think I would trust the wideband in that log at all, it is still pegged at the leanest value it can read even at the end of the log.  As a quick validation when you next to a cold start and it is not running good, try adding or subtracting say 5ms from the master fuel to see if it improves when you make it leaner or richer.  

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Heres a log i took this morning, Didnt go full lean the entire time when idle stabalized. Just stalls out from full lean, Let the iac reset then fire back up and its full lean for alittle bit before it goes back to normal. ITs only lean on the spots where it doesnt want to idle correctly.

https://www.dropbox.com/scl/fi/71zd1g6s3pfxarv3mdanp/PC-Datalog-2023-11-21-1-07-35-pm-cold-start-update.llgx?rlkey=n09cb2mbhsqeg1jupob7t3vok&dl=0

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