IAC, vacuum, and idle... Any ideas ?
Re: IAC, vacuum, and idle... Any ideas ? Thanks for the post. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
I am watching the desired vs. actual IAC with AutoTap and they are right on, so I wouldn't think it's a bad IAC stepper motor... What is it about the stock TB that you think will help ?
If I put a stock TB on would it need the bigger hole in the blade, or do you just mean to play with the idle set screw to try to get it to idle ?
Thanks for the help...
Rob (Bad30th)
I am watching the desired vs. actual IAC with AutoTap and they are right on, so I wouldn't think it's a bad IAC stepper motor... What is it about the stock TB that you think will help ?
If I put a stock TB on would it need the bigger hole in the blade, or do you just mean to play with the idle set screw to try to get it to idle ?
Thanks for the help...
Rob (Bad30th)
IAC, vacuum, and idle... Any ideas ? OK folks, help me out here.
I am trying to get the idle smooth enough with the new engine combo to get the crank position relearn done at the dealer. Every time it's revved above 3k it comes down and almost stalls.
Specifics :
Stage 2 ported heads
222/224 .571/.571 114 cam
Ed Wright tuning, set to 900rpm idle speed
macs w/ (new) CarSound cats
ported TB
hole in TB 1/4", started a 2nd hole 3/32"
IAC counts at cold start in Park are 100+, slowly dropping to 0 in park when warm. With 0 IAC in park, it jumps to 50-60 when put in gear.
It will idle OK once it's warmed up but has problems with cold starts, hot starts, and coming down from a rev over 3k.
So, questions :
- vacuum leak ? what should a vac guage read ? hook it up to the brake booster hose ?
- any ideas on why the stumble after a rev ?
- why is the IAC so high at startup then drops to 0 ? Why the big change when it's put in gear ?
Thanks for any ideas/help...
Rob (Bad30th)
<small>[ October 17, 2002, 12:28 PM: Message edited by: BadAss30th ]</small>
I am trying to get the idle smooth enough with the new engine combo to get the crank position relearn done at the dealer. Every time it's revved above 3k it comes down and almost stalls.
Specifics :
Stage 2 ported heads
222/224 .571/.571 114 cam
Ed Wright tuning, set to 900rpm idle speed
macs w/ (new) CarSound cats
ported TB
hole in TB 1/4", started a 2nd hole 3/32"
IAC counts at cold start in Park are 100+, slowly dropping to 0 in park when warm. With 0 IAC in park, it jumps to 50-60 when put in gear.
It will idle OK once it's warmed up but has problems with cold starts, hot starts, and coming down from a rev over 3k.
So, questions :
- vacuum leak ? what should a vac guage read ? hook it up to the brake booster hose ?
- any ideas on why the stumble after a rev ?
- why is the IAC so high at startup then drops to 0 ? Why the big change when it's put in gear ?
Thanks for any ideas/help...
Rob (Bad30th)
<small>[ October 17, 2002, 12:28 PM: Message edited by: BadAss30th ]</small>
Re: IAC, vacuum, and idle... Any ideas ? IN gear IAC is generally 20 - 30 higher. you try adjusting the blade via the set screw. 0 IAC means too much air in park; you might try closing the TB and see if that helps. Why are you reving to 3k?
Re: IAC, vacuum, and idle... Any ideas ? The revving to 3k thing is part of the crank position relearn. The relearn envolves the tech revving the motor to 4500rpm with the Tech II attached, letting it come back down to idle the ECM learns the crank position. The idle stumbles so bad when it comes down from the rev the Tech II can't relearn the crank position.
Here's something else odd I noticed today. If I pump my foot on the brake the idle raises slightly, and when I stop pumping the brake the idle stumbles. I'll be looking it over top to bottom this weekend for vacuum leaks (that's the only connection I can think of, the brake booster runs on vacuum)...
Thanks for any help...
Rob (Bad30th)
<small>[ October 18, 2002, 05:24 PM: Message edited by: BadAss30th ]</small>
Here's something else odd I noticed today. If I pump my foot on the brake the idle raises slightly, and when I stop pumping the brake the idle stumbles. I'll be looking it over top to bottom this weekend for vacuum leaks (that's the only connection I can think of, the brake booster runs on vacuum)...
Thanks for any help...
Rob (Bad30th)
<small>[ October 18, 2002, 05:24 PM: Message edited by: BadAss30th ]</small>
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Re: IAC, vacuum, and idle... Any ideas ? If your IAC count is below 30 in park, that could be causing the problem.. The desired IAC count in park should be between 30 and 50.. No more then 120 with AC on in Gear.
It sounds to me that your idle set screw is to far in or you hole in the blade is to big. You can rivet the hole and start over..
It sounds to me that your idle set screw is to far in or you hole in the blade is to big. You can rivet the hole and start over..
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Joined: Nov 2001
Posts: 1,684
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From: Yarmouth, MA
Re: IAC, vacuum, and idle... Any ideas ? when my iac count was real low like yours, it ran crappy, surging, wouldn't idle down. I think the ported tb with the drilled hole was the problem. I am going to try to get the hole smaller and retune. With my iac's at 30 or so its almost perfect.
Re: IAC, vacuum, and idle... Any ideas ? Thanks for the post.
The IAC at startup (in Park)is 200, slowly dropping to 0 when warmed up. The issue is really only at startup, when the IAC is waaaay high. After it warms up it idles OK. (Won't stall or surge during normal driving).
When it drops to 0 in Park (after it's warmed up), putting it in gear makes the IAC shoot up to about 60.
Going to go over the motor this afternoon really close and try the ol' carb cleaner spray trick to look for vacuum leaks.
Thanks for the help fellas.
Rob (Bad30th)
The IAC at startup (in Park)is 200, slowly dropping to 0 when warmed up. The issue is really only at startup, when the IAC is waaaay high. After it warms up it idles OK. (Won't stall or surge during normal driving).
When it drops to 0 in Park (after it's warmed up), putting it in gear makes the IAC shoot up to about 60.
Going to go over the motor this afternoon really close and try the ol' carb cleaner spray trick to look for vacuum leaks.
Thanks for the help fellas.
Rob (Bad30th)
Re: IAC, vacuum, and idle... Any ideas ? ARGH !
Tried again at the dealer today to get the crank relearn done. It wouldn't do it, I watched the tech try to do it. Even pumping the brake wasn't good enough for the relearn, although it made the idle land much more softly from the rev with less stumbling. Still stumbles a lot.
Let's start with the basics - what would cause a stumble after a high rev ?
Thanks for any help, I need to get this fixed.
Rob (Bad30th)
Tried again at the dealer today to get the crank relearn done. It wouldn't do it, I watched the tech try to do it. Even pumping the brake wasn't good enough for the relearn, although it made the idle land much more softly from the rev with less stumbling. Still stumbles a lot.
Let's start with the basics - what would cause a stumble after a high rev ?
Thanks for any help, I need to get this fixed.
Rob (Bad30th)
Re: IAC, vacuum, and idle... Any ideas ? TTT, help me out fellas ! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
Rob (Bad30th) <img border="0" alt="[Firebird]" title="" src="graemlins/formula.gif" />
<small>[ October 24, 2002, 02:29 PM: Message edited by: BadAss30th ]</small>
Rob (Bad30th) <img border="0" alt="[Firebird]" title="" src="graemlins/formula.gif" />
<small>[ October 24, 2002, 02:29 PM: Message edited by: BadAss30th ]</small>
Re: IAC, vacuum, and idle... Any ideas ? Update :
Mark@AAP and I took the car to a GM dealer up by his shop, where he knows one of the techs. They were unable to get the crank relearn done with the FastChips ECM, BUT...
They swapped in a new ECM, downloaded the factory program, and successfully performed the crank position relearn !
This means there's something screwy with the Ed Wright ECM. Either his locked-out programming can't communicate with the Tech II, or something is wrong physically with the ECM itself. I have also had some other glitches with the TCS/ABS system, so I'm leaning towards the latter.
So, the even better news is that I am having the new factory ECM (that successfully performed the relearn) programmed with LS1 Edit. This will actually be better for me going forward since I won't need to ship the ECM back and forth (and pay $150) for Ed Wright to update it every time I change something. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
I'll make an update post next week when the new ECM arrives and is installed...
Happy driving,
Rob (Bad30th)
Mark@AAP and I took the car to a GM dealer up by his shop, where he knows one of the techs. They were unable to get the crank relearn done with the FastChips ECM, BUT...
They swapped in a new ECM, downloaded the factory program, and successfully performed the crank position relearn !
This means there's something screwy with the Ed Wright ECM. Either his locked-out programming can't communicate with the Tech II, or something is wrong physically with the ECM itself. I have also had some other glitches with the TCS/ABS system, so I'm leaning towards the latter.
So, the even better news is that I am having the new factory ECM (that successfully performed the relearn) programmed with LS1 Edit. This will actually be better for me going forward since I won't need to ship the ECM back and forth (and pay $150) for Ed Wright to update it every time I change something. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
I'll make an update post next week when the new ECM arrives and is installed...
Happy driving,
Rob (Bad30th)
