my idle rpm is already set a little high because of my engine setup but i need to adjust my startup rpm. when i start my truck the rpm shoots up pretty high and then comes back down and now its getting colder and it is going even higher than during the summer. do i adjust the table named IAC% flow vs. temperature (P/N) to bring it down some ?
what ecm are you using?
i have a 16168625 with a $oD bin modified BJYL .Originally Posted by ony
I am not up on the 625's ,sure someone will give some advise.
I can probably help you. If you want, post your bin and I can take a look at it this evening
Seems like I had same issue especially when temps cooled off. Best I can remember I reduced start up spark advance. Watch your spark advance at start while connected to tunerpro. Believe happens when you heavily modify the stock timing tables. I cut the spark added figures in half.
89 K1500 Scottsdale 5.7L 5spd 3:42 RamJet cam Dart iron TBI heads 427 PCM swap
95 C2500 Cheyenne 6.5L turbo diesel 4L80e 4:10 DB2-4911 Manual pump conversion 0411 PCM trans control 2Bar COS
05 Outback XT 2.5L turbo gas auto
here it is. just a little about my setup i have a frankenbody which is a four barrel TBI i made from two gm throttle bodies.it already idles between 750-800 .i already lowered the idle rpm timing to try and bring it down more . as far as starup timing i will have to look at that. i was looking at a recording and the IAC started at 150 and quickly came down to about 35 then came down more as it warmed up. i was thinking if i could get it to start at less than 150 that would help.
Right now at normal operating temps, It is set to idle at approximately 775. Is it the initial flare up or the idle rpm until it warms up that you want to lower? What transmission are you running? This PCM basically has 4 idle speed tables and a few adders. If you are using a 4L60e and A/C input to PCM, you will have to adjust all 4 tables. If a 700R4 (4L60) and no A/C input, you just have to adjust 1 table and maybe an adder for idle. The initial flare up doesn't last but a few seconds. The temperature based idle takes however long it takes to warm up from cold and the initial rpm is higher the colder it gets. See attached screenshot for table locations.
Last edited by sturgillbd; 10-19-2014 at 04:37 AM. Reason: ask about trans
If you want to speed up the decay of the initial flare up look at the table IAC Cold Offset Delay vs. Temperature in IAC Tables. At 68 degrees it takes 14 seconds for the initial IAC counts to decay to normal idle range.
the 775 idle is fine my problem is at 47 degrees the other morning when i started the truck the rpm shot up to 2000 rpm for a couple of seconds then came down to warmup idle speed. at 47 degrees the IAC showed 150 upon startup and quickly came down to 35 then slowly worked its way down as it warmed up . at 90 degrees the IAC showed 88 and then came down. im wondering if there is a way to adjust so that the IAC doesnt open to 150?
i was looking at the recording again and even tho it was 47 outside the engine was 73 degrees and showed IAC 150 i wonder what it will be when the engine is 47 degrees?
I adjusted the IAC Cold Offset delay table in this bin. See if this helps.
i will try it thanks
You can adjust how far the IAC is open at startup via the table you first mentioned. When I was first trying to get my idle the way I wanted it, I adjusted that table with mixed results. I am finishing up some bodywork and painting on my project and soon I will be able to get back to my tuning work on mine using $0D. If that edit on your bin doesn't help, message back and I'll adjust the initial IAC airflow and we can see what happens. Just keep your original bin and then you can do a bin compare to see what has changed and by how much.
Brian
Did you ever try the edited bin?
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