idle setting procedure on L98 TPI
Thread Starter
Burning Brakes
Joined: Nov 2000
Posts: 810
Likes: 4
From: Austria
idle setting procedure on L98 TPI
Hi all,
i installed an airfoil on my 90 L98, cause i got it for free, and now sometimes idle is too low, sometimes, especially, when climate compressor engages, it dies..otehrwise it ran really fine, and pull strong...
what i want to know..
have anybody of you the procedure to set idle?
i have a description, that have to do with the IAC, the ALDL, aso..
do you agree?
any answers would be nice
Thanks :cheers:
i installed an airfoil on my 90 L98, cause i got it for free, and now sometimes idle is too low, sometimes, especially, when climate compressor engages, it dies..otehrwise it ran really fine, and pull strong...
what i want to know..
have anybody of you the procedure to set idle?
i have a description, that have to do with the IAC, the ALDL, aso..
do you agree?
any answers would be nice
Thanks :cheers:
Team Owner
Joined: Sep 2001
Posts: 62,161
Likes: 1,733
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Re: idle setting procedure on L98 TPI (corvette90)
set the TPS voltage to .57 VDC i believe, disassemble and clean the IAC
Burning Brakes
Joined: Jan 2000
Posts: 1,015
Likes: 3
From: Esko MN
Re: idle setting procedure on L98 TPI (vader86)
Sometimes your butterflies can be closed too tight and not letting enough air in. you'll know this if they're sticking in the closed position. There's a torx screw on the driver's side, top of the throttle body. It will adjust the opening of the butterflies.
Greg
Greg
Drifting
Joined: Nov 2001
Posts: 1,783
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From: Latham NY
Re: idle setting procedure on L98 TPI (corvette90)
See Tech Tip below but you may need to set the minimum idle slightly higher (450-500).
www.corvetteforum.com/techtips/viewsubtopic.php?SubTopicID=55&TopicID=2
www.corvetteforum.com/techtips/viewsubtopic.php?SubTopicID=55&TopicID=2
Burning Brakes
Joined: Nov 2000
Posts: 1,040
Likes: 2
From: BowlingGreen KY
Re: idle setting procedure on L98 TPI (corvette90)
Jumper pins a & b. Unplug timing connector under hood by the ecm. Turn ignition on but do not start car. Wait 30 - 40 seconds. Unplug IAC connector. Unjumper pins A&b and start car. Keep it running with the gas and adjust idle to about 450 to 550 rpm. Turn car off. Plug IAC back in plug the timing connector back up and start car again. It probably won't run right the first time you restart it so turn it off and restart one more time. If your factory tach is off you will have a hard time getting it set right. My factory tach was off by 650 rpms at idle. I always thought I had a high idle problem until I installed an aftermarket tach.
Le Mans Master
Joined: Aug 2000
Posts: 5,192
Likes: 1
From: Airport Cruise-in 1 Veteran Airport Cruise-in 2 Veteran
Cruise-In II Veteran
Re: idle setting procedure on L98 TPI (KYVette90)
Unplug timing connector under hood by the ecm.
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Burning Brakes
Joined: Jan 2000
Posts: 1,015
Likes: 3
From: Esko MN
Re: idle setting procedure on L98 TPI (corvette90)
90,
Take the air duct off the TB and start the engine. Check the air flow into the TB. If it seems to be sucking only through the little hole at the base of the airfoil, THEN you adjust the set screw on the TB so the butterflies open slightly. Sorry I didn't clarify! It's got nothing to do with the rest of the idle adjustment as far as I know.
Greg
Take the air duct off the TB and start the engine. Check the air flow into the TB. If it seems to be sucking only through the little hole at the base of the airfoil, THEN you adjust the set screw on the TB so the butterflies open slightly. Sorry I didn't clarify! It's got nothing to do with the rest of the idle adjustment as far as I know.
Greg
Le Mans Master
Joined: Dec 1999
Posts: 8,540
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From: And on the fifth day, subpoenas were served to Obama senior staff
Re: idle setting procedure on L98 TPI (Greg Johnson)
You set the minimum air adjustment using the little set screw on the TB, this is how you set to say 500-550 RPM. Once set using the proceedure in the tech tips, do not touch the screw again (unless you go through the whole proceedure). I was able to set mine with the timing wire connected, if you have a hard time getting it to idle you can disconnect the wire.
Pete
Pete
Race Director
Joined: Aug 2000
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Cruise-In II Veteran
Re: idle setting procedure on L98 TPI (PeteL)
Pete's right and BTW you should never touch the TB screw unless you were going to readjust the minimum air speed.
I find it interesting you installed the air foil and now it wont idle right at times.I think you may have reused the gasket for the TB cover and if so replace it with a new one.
While a vacuum leak can sometimes cause a higher idle,it wont suprise me if thats causing the idle speed to drop out.
The TPS on certain years isnt adjustable either.
In other words,remove the air foil and see if the problem goes away.Do not reuse the old TB cover gasket either.
:)
I find it interesting you installed the air foil and now it wont idle right at times.I think you may have reused the gasket for the TB cover and if so replace it with a new one.
While a vacuum leak can sometimes cause a higher idle,it wont suprise me if thats causing the idle speed to drop out.
The TPS on certain years isnt adjustable either.
In other words,remove the air foil and see if the problem goes away.Do not reuse the old TB cover gasket either.
:)
Burning Brakes
Joined: Nov 2000
Posts: 1,040
Likes: 2
From: BowlingGreen KY
Re: idle setting procedure on L98 TPI (Bill's86Coupe)
I think sometimes, the problem with the airfoil affecting the idle is caused by the airfoil restricting air flow through the IAC air passage. The airfoils bolt right over the hole where the IAC air flows through. If it is really messing with your idle you might want to just remove it completely.
