Hunting idle/IAC ??
07-04-2009, 11:07 AM
#1
2nd Gear Member
Thread Starter
Join Date: Jan 2007
Posts: 308
Hunting idle/IAC ??
My 93GT started hunting for idle recently,does not do this all the time. When I come to a stop it will want to stall, then rpm back up, over and over (again not everytime I stop). Pulled KOEO/KOER= no codes, cleaned IAC, cleaned MAF, TPS voltage @ .96. no vac leaks I can find. I'm thinking it's the IAC because, when I unplugged it there was no idle difference. Did HCI upgrade last year and did not have this issue. Just a weekend/nice weather cruiser but I want to get it right. Cam is a Steeda#18
07-05-2009, 11:22 AM
#5
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Join Date: Jan 2006
Location: Puerto Rico
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09-22-2009, 04:38 PM
#6
Join Date: Sep 2009
Location: Michigan
Posts: 1
My '89 was exhibiting these exact symptoms. After cleaning IAC with no improvements I ended up replacing it which solved the problem. I also noticed that it made no difference to the idle when I unplugged the IAC so am guessing the motor/actuator quit working after 111K miles.
09-22-2009, 11:26 PM
#7
5th Gear Member
Join Date: Mar 2006
Location: Massachusetts, New Bedford
Posts: 3,035
well how did u clean the iac? just soak it w/ carb cleaner? the inner little shaft thing should move if you push one it as well as twist. mine was stuck. so soak it with carb cleaner and make sure you can spin and move the shaft inside it.
09-23-2009, 08:15 AM
#8
2nd Gear Member
Thread Starter
Join Date: Jan 2007
Posts: 308
Just to update, since this thread has seem to come to life again. I reset the base idle and cleaned the iac. That seemed to do the trick, although occasionally I will get a small idle fluctuation, but 100 times better than it was. Thanks for everyones help!
09-29-2009, 07:22 PM
#10
6th Gear Member
Join Date: Nov 2006
Location: Spfld, MA
Posts: 9,240
Base Idle Reset Procedure
1. Clean TB with carb cleaner and nylon brush (toothbrush size). Engine off, fully open TB blade and spray/brush TB until all gunk and oil residue is cleaned.
2. Allow to dry, or close TB blade and start engine until it clears all carb cleaner fumes/liquid.
3. Let engine idle...if it doesn't, increase idle speed via TB stop screw until engine stays idling on its own.
4. Disconnect IAC valve, if engine dies repeat 3 with IAC disconnected.
5. Set idle speed to the lowest setting possible between 650-850 rpms with IAC disconnected. It is key to use the lowest possible to prevent idle surge, rolling, etc once the IAC is connected as follows.
6. Turn engine off, and reconnect IAC
7. With Ign On Eng Off, check TPS voltage output....if it's between .8vdc - 1.0vdc, it's OK. This voltage check should be done between the Green and Black wires at the TPS side connector as shown in the pic below (FYI: Green = TPS Signal, Black = SIGRTN, and Orange = VREF)....(-) terminal of the DVOM on the Black wire and (+) terminal on the Green wire.
8. Disconnect battery (-) for 3-4 minutes.
9. Reconnect battery, start engine, allow it to idle for 2-4 minutes to confirm setup,
10. If idle speed falls too low or stalls, increase idle speed via the TB set screw a little at a time.
11. Turn engine off for 20 seconds, re-start engine and repeat 9 - 11 if required.
12. Reconfirm TPS output is within the .8vdc - 1.0vdc range optimum range.
NOTES:
1. No need to reset ECM KAM (reset computer), the TPS minimum value used for idle control, is reset automatically by the EEC-IV every time the ign is cycled on-off for 20 seconds-on.
2. If the TPS output is within 6vdc - 1.1vdc, it's still acceptable, since no TPS failure codes will be generated, and it falls within the EEC-IV .5vdc - 1.19vdc working range.
13. Allow a 10-20 minute "relearning" period under normal driving conditions (drive cycle).....you're done!
1. Clean TB with carb cleaner and nylon brush (toothbrush size). Engine off, fully open TB blade and spray/brush TB until all gunk and oil residue is cleaned.
2. Allow to dry, or close TB blade and start engine until it clears all carb cleaner fumes/liquid.
3. Let engine idle...if it doesn't, increase idle speed via TB stop screw until engine stays idling on its own.
4. Disconnect IAC valve, if engine dies repeat 3 with IAC disconnected.
5. Set idle speed to the lowest setting possible between 650-850 rpms with IAC disconnected. It is key to use the lowest possible to prevent idle surge, rolling, etc once the IAC is connected as follows.
6. Turn engine off, and reconnect IAC
7. With Ign On Eng Off, check TPS voltage output....if it's between .8vdc - 1.0vdc, it's OK. This voltage check should be done between the Green and Black wires at the TPS side connector as shown in the pic below (FYI: Green = TPS Signal, Black = SIGRTN, and Orange = VREF)....(-) terminal of the DVOM on the Black wire and (+) terminal on the Green wire.
8. Disconnect battery (-) for 3-4 minutes.
9. Reconnect battery, start engine, allow it to idle for 2-4 minutes to confirm setup,
10. If idle speed falls too low or stalls, increase idle speed via the TB set screw a little at a time.
11. Turn engine off for 20 seconds, re-start engine and repeat 9 - 11 if required.
12. Reconfirm TPS output is within the .8vdc - 1.0vdc range optimum range.
NOTES:
1. No need to reset ECM KAM (reset computer), the TPS minimum value used for idle control, is reset automatically by the EEC-IV every time the ign is cycled on-off for 20 seconds-on.
2. If the TPS output is within 6vdc - 1.1vdc, it's still acceptable, since no TPS failure codes will be generated, and it falls within the EEC-IV .5vdc - 1.19vdc working range.
13. Allow a 10-20 minute "relearning" period under normal driving conditions (drive cycle).....you're done!
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