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Thread: How to make it 'rev up' upon cold start 7747

  1. #1
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    How to make it 'rev up' upon cold start 7747

    So I've been working with the 16144288 ECM in my new Jeep J20 project with a 4.3L v6. I've noticed that upon cold start, the engine revs way up, then slowly backs down to the target idle. Sort of like giving it gas during startup. This really seems to makes for a very 'healthy' cold start and I like that.

    So how do I make the ASDU bin file in my other jeep do the same thing? I messed with the IAC target idle in TP but that doesn't seem to do it.

  2. #2
    EFI GearHead ! EagleMark's Avatar
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    Use the Park/Neutral wire. Ground while in P/N and open when in drive.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    I don't have the P/N wire connected on any of my TBI conversions.

    I'll try it though...

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    EFI GearHead ! EagleMark's Avatar
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    Not sure why the 16144288 ECM does it? Maybe it was a manul bin to start with?

    That is how the 1227747 ASDU Auto bin works.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Yeah, I dunno. I haven't modded the 288 ECM for a ZIF socket yet, so I haven't messed with it at all (or even looked up the bin).

    Here is what Bill over at the binderplantet FI FAQ's says;

    B10-orn/blk- Park/Neutral sw. This is optional but I have hooked it into the park sw on the tranny. It tells the ECM when you are in Pk or N. It can be used to give a slight adjustment to idle speed when switching from park to drive and back.

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    EFI GearHead ! EagleMark's Avatar
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    That's what a lot of people think the wire is for. Not true, it changes the entire IAC routine in the ECM, in P/N the ECM has limited ability, like high and low, you get somewhere in there. In Drive you get complete IAC control of engine along with many other Idle Paremeters that involve fueling, IAC, O2, etc!

    Many people have bought aftermarket wiring harness and last I checked Painless instructions are still wrong/backwards and no one can get a decent idle. Other aftermarket harness companies have a blank spot next to B10... and no instructions.

    To understand more on how it really works read the paper written on IAC logic 13 years ago.
    http://www.gearhead-efi.com/Fuel-Inj...pdated-12-4-00

    There are other ways to get the flare up when cold and TunerPro bin definition has the paremeters to do so, TunerCat does not. It works in manual stock bins but near as good as auto bins. But it would not include the IAC logic to soften change into gear. P/N switch is easy and a good addition to a conversion.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

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    OK cool - so your saying that I should try wiring B10 into the tranny NSS so that B10 is grounded when in park or neutral and then open in when it's in gear?

    I think I can do that.

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    EFI GearHead ! EagleMark's Avatar
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    Not sure what a NSS is but yes you have the right idea. Remember when grounded it will idle highrer. If you ever do an min air adjustment it has to be done in gear or open wire to B10, really screws with people when they can't get it right in P/N.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

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    NSS = Neutral Safety Switch.

    thanks for your help. I'm actually gonna go try and ground B10 and see what it does now...

  10. #10
    EFI GearHead ! EagleMark's Avatar
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    I forget if the NSS can do it? Or it needs a ground relay off it.

    Either way you got what needs to be done. If you ground the wire I can forsee the future! You will get your high cold idle, but will not like how it drives at all...

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  11. #11
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    LOL yeah. I connected B10 to a good ground and started it up. I didn't notice any apparant difference in the idle (it was fully warmed up already). I am pretty sensitve to the idle 'cause this Jeep is lifted with 35" tires and has lots of slop in the driveline, producing a pretty good 'clunk' when shifting from park to drive (caused by numerous issues). This is aggravated by a high idle.

    I'm gonna leave it connected and drive it 5 miles to work. Will report back then...

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    Connecting B10 to ground didn't make any change at all. I just left it connected to ground the whole time. I may have it set for manual tranny in the BIN...

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    EFI GearHead ! EagleMark's Avatar
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    Maybe? I've never tested an Auto bin with manual set for results. But when I did test this by disconnecting the B10 wire on a factory stock ADSU truck, the results were horrible. High idle always, banging in gear etc...

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  14. #14
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    I checked in TP and sure enough - manual tranny.

    I'll change it to automatic and see what happens...

  15. #15
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    Ok so I grounded B10 to a known good ground. I also swapped ECM's. It still has no hint of any kind of a 'rev up' upon start (cold or hot).

    This is an AMC 401 with a stock rebuild. Morning temps have been in the single digits (F).

    Any idea why? Here is my bin (keep in mind that I've done 0 data logging on this rig)

    http://blakeoffroad.com/vps/Attachments/waggy-401.bin

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