This look right?? Throttle Blade Position
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Race Director
Joined: Mar 2004
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From: Fort Wayne IN
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This look right?? Throttle Blade Position
Pics first:
Symptoms are an uncommanded startup flare to 2000-2400 RPM, and a mildly unstable idle. Tuner wanted me to pull TB and have a look, and here I am. The throttle blade is actually open and angled (hard to show with pictures). I can push it shut but it springs back to this preset position. Fully shut there's a nice seal around the blade, but sitting open like this is allowing a LOT of bypass air into the motor. Is there anything that can be done about this, is it even normal, or is it as simple as me pulling the motor and moving the gears to where it's shut and reassembling??
Symptoms are an uncommanded startup flare to 2000-2400 RPM, and a mildly unstable idle. Tuner wanted me to pull TB and have a look, and here I am. The throttle blade is actually open and angled (hard to show with pictures). I can push it shut but it springs back to this preset position. Fully shut there's a nice seal around the blade, but sitting open like this is allowing a LOT of bypass air into the motor. Is there anything that can be done about this, is it even normal, or is it as simple as me pulling the motor and moving the gears to where it's shut and reassembling??
Drifting
Joined: Dec 2006
Posts: 1,523
Likes: 5
From: Holly, Michigan
Not what I was looking for, but if you clink on the link, it appears in the various pics that the LSX TB's are canted slightly open in the relaxed state...
http://www.s2performance.net/vettepage.html
http://www.s2performance.net/vettepage.html
Tech Contributor
Joined: Dec 1999
Posts: 32,910
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
The LS engine TB does NOT have a blade stop and when the engine is OFF and the key is off,,the Throttle Blade does NOT seat and can be moved easilt against the spring.
When you turn the KEY to ON,,the Throttle blade should errect to the last known or commanded idle position. When its powered up, you will see that it will have a slight opening to allow in the correct idle air.
Examine it with the key on. If you have some one press the accelerator you can watch the blade respond. Make sure tht it goes wide open.
When you turn the KEY to ON,,the Throttle blade should errect to the last known or commanded idle position. When its powered up, you will see that it will have a slight opening to allow in the correct idle air.
Examine it with the key on. If you have some one press the accelerator you can watch the blade respond. Make sure tht it goes wide open.
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Race Director
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From: Fort Wayne IN
2025 C5 of the Year Finalist - Modified
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I know it's got to be closing down because we're getting the 850 RPM commanded idle (albeit a little unstable, searching +-50ish RPM), but the uncommanded flare to 2000 RPM is what's concerning us. The tuner had to do a TON of work to get 500 RPM knocked off of the flare and wasn't able to get it down any further. I'm going to go plug it in and flip the key on to see what it does.
Thread Starter
Race Director
Joined: Mar 2004
Posts: 12,466
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From: Fort Wayne IN
2025 C5 of the Year Finalist - Modified
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NOT commanding shut. Apparently it's where the computer thinks it should be.
What else would cause a uncommanded start up flare like I'm getting?
What else would cause a uncommanded start up flare like I'm getting?
Racer
Joined: May 2009
Posts: 263
Likes: 1
From: Andover KS
I replaced my throttle body that was normally shut all the way with power off on a 2000 with one from a 2003 and it looks exactly like yours does. I could push it closed but its "relaxed" position is slightly open and it would idle high with a slight roughness. I did the idle re-learn and it fixed it mostly. It idles smooth around 750-800 RPM but I think the old one would idle lower than that. Runs well though so I just live with it. (6spd)
Safety Car
Joined: Sep 2003
Posts: 3,558
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From: Cape Coral FL
Not knowing what your tuner did to get it calm the flare down a little at start I can offer you this info.
I use EFILive but I believe there are similar tables used in HPTuners.
In the idle section there are several tables used regarding startup params. The one I found to be most useful in helping with startup flare was 'Startup Friction Airflow'. It is a temperature weighted curve that is supposed to add air to compensate for 'cold stiff' engine components at startup. I pulled the curve down and it did a good job compensating for the flare.
Your resting blade angle is normal. However the body has been extensively flared and ported causing the airflow to change. You wil have to program the pcm to compensate for that.
Take heart. I did it to mine and now it is nice and tame at startup.
I use EFILive but I believe there are similar tables used in HPTuners.
In the idle section there are several tables used regarding startup params. The one I found to be most useful in helping with startup flare was 'Startup Friction Airflow'. It is a temperature weighted curve that is supposed to add air to compensate for 'cold stiff' engine components at startup. I pulled the curve down and it did a good job compensating for the flare.
Your resting blade angle is normal. However the body has been extensively flared and ported causing the airflow to change. You wil have to program the pcm to compensate for that.
Take heart. I did it to mine and now it is nice and tame at startup.
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Thread Starter
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Joined: Mar 2004
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From: Fort Wayne IN
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I'm going to do an idle relearn because I don't think it was ever done. Have to get the fuel pumps back int he car first and then we'll see what happens.
Melting Slicks
Joined: Jul 2007
Posts: 2,939
Likes: 7
From: Simpsonville SC
St. Jude Donor '09-'10
YES! It is normal for the throttle blade to be partially open under power. I went through a similar issue when I installed a Lingenfelter 90MM TB. I learned that the throttle position needs to be arount 6-7% open at idle. I had to adjust an intial idle air parameter to get my car to keep from running up to 3500 RPM on a cold start. I still need to tweak mine as it still runs up to maybe 2000 RPM for a few seconds on a COLD start.
Thread Starter
Race Director
Joined: Mar 2004
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From: Fort Wayne IN
2025 C5 of the Year Finalist - Modified
C5 of Year Finalist (performance mods) 2019
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Thanks guys. Hopefully my tank to pump seal comes in today (It better, I paid $30 for overnight shipping) and I can get it back together and an idle relearn done/some miles put on.
Burning Brakes
Joined: Mar 2003
Posts: 1,156
Likes: 2
From: Arlington VA
Not knowing what your tuner did to get it calm the flare down a little at start I can offer you this info.
I use EFILive but I believe there are similar tables used in HPTuners.
In the idle section there are several tables used regarding startup params. The one I found to be most useful in helping with startup flare was 'Startup Friction Airflow'. It is a temperature weighted curve that is supposed to add air to compensate for 'cold stiff' engine components at startup. I pulled the curve down and it did a good job compensating for the flare.
Your resting blade angle is normal. However the body has been extensively flared and ported causing the airflow to change. You wil have to program the pcm to compensate for that.
Take heart. I did it to mine and now it is nice and tame at startup.
I use EFILive but I believe there are similar tables used in HPTuners.
In the idle section there are several tables used regarding startup params. The one I found to be most useful in helping with startup flare was 'Startup Friction Airflow'. It is a temperature weighted curve that is supposed to add air to compensate for 'cold stiff' engine components at startup. I pulled the curve down and it did a good job compensating for the flare.
Your resting blade angle is normal. However the body has been extensively flared and ported causing the airflow to change. You wil have to program the pcm to compensate for that.
Take heart. I did it to mine and now it is nice and tame at startup.
Thread Starter
Race Director
Joined: Mar 2004
Posts: 12,466
Likes: 886
From: Fort Wayne IN
2025 C5 of the Year Finalist - Modified
C5 of Year Finalist (performance mods) 2019
2017 C5 of the Year Finalist
2016 C5 of the Year Finalist
2015 C5 of the Year Finalist
Idle relearn did jack. Still flaring to 1900-2100 RPM. Everything is functioning because the tuner had at least cut the flare time from 5 to 3 seconds. Hopefully some more tuning will clear it up.
Thread Starter
Race Director
Joined: Mar 2004
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From: Fort Wayne IN
2025 C5 of the Year Finalist - Modified
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Swapped on a stock TB, startup flare goes to about 1300-1500 RPM MAX and settles right down. I compared the two and on the ported one there was just a TON of material taken off of the floor and roof and you could obviously see how much air could get past there. Bummer.....
Burning Brakes
Joined: Apr 2008
Posts: 877
Likes: 4
From: Nouvelle Ecosse
I think that it's common for ported TB's to have a slight flare...on bone cold startup mine will flare to 2000 rpms for maybe 2 seconds, then down to 1200 then down to ~750. Hot start it just fires up...no flare... and idles really well.
It seemed to respond better after the idle relearn. With a ported TB this really needs to be done.
It seemed to respond better after the idle relearn. With a ported TB this really needs to be done.
