High Idle
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Joined: Dec 2008
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High Idle It is stock 1999 LS1 Camaro with headers only.
It started after taking it radiator shop for cleaning the radiator. Rad was removed out of the car and put back after cleaning.
When started, it idles fine below 1000 rpm. Once I give it gas, it climbs to about 1800 rpm and stays there unitl I switch it off and restart it, then it goes again once I step on the gas.
When I unpluged the IAC, it goes down to 1000 rpm. When I plug it again, it goes back to high idle.
I tried and reset the TPS by unplugging the connector while key is off, switched key on for seconds then key off and plugged it again and started the car but it did not resolve it.
I removed the IAC, cleaned it and put it back. Nothing changed.
It was idling fine untill I took it radiator shop.
What could be the problem??? and how to resolve it?
I've done a scan using HP Tuners and found these codes: P0405, P0134, P0154, P1637. I reseted them but P0405, EGR, goes back right away.
Checked the target idle using HP Tuners editor and it is right at 500rpm when hot.
Tune file is attached.
It started after taking it radiator shop for cleaning the radiator. Rad was removed out of the car and put back after cleaning.
When started, it idles fine below 1000 rpm. Once I give it gas, it climbs to about 1800 rpm and stays there unitl I switch it off and restart it, then it goes again once I step on the gas.
When I unpluged the IAC, it goes down to 1000 rpm. When I plug it again, it goes back to high idle.
I tried and reset the TPS by unplugging the connector while key is off, switched key on for seconds then key off and plugged it again and started the car but it did not resolve it.
I removed the IAC, cleaned it and put it back. Nothing changed.
It was idling fine untill I took it radiator shop.
What could be the problem??? and how to resolve it?
I've done a scan using HP Tuners and found these codes: P0405, P0134, P0154, P1637. I reseted them but P0405, EGR, goes back right away.
Checked the target idle using HP Tuners editor and it is right at 500rpm when hot.
Tune file is attached.
Thread Starter
TECH Resident
Joined: Dec 2008
Posts: 995
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Ok. Here is what I found out. TB sticks at partially open. It does not close 100%.
I foreced it by hand and it would idle perfect. Done this several times and it idles perfect when I force TB by hand. However, it does not go back to close by itself.
I think it is the spring or the TB blade shaft.
So, I took out the TB, removed the TPS and cleaned TB with WD40 and sprayed the shaft from both sides. Sprayed the spring. Cycled TB from close to open by hand several times.
I adjusted the TB screw out to make the blade close more.
Put it back and it did the same. When I give it gas, it idles at 1800rpm. It does not idle down until I force the TB back.
Do I need to replace TB or it could be the throttle cable???
I foreced it by hand and it would idle perfect. Done this several times and it idles perfect when I force TB by hand. However, it does not go back to close by itself.
I think it is the spring or the TB blade shaft.
So, I took out the TB, removed the TPS and cleaned TB with WD40 and sprayed the shaft from both sides. Sprayed the spring. Cycled TB from close to open by hand several times.
I adjusted the TB screw out to make the blade close more.
Put it back and it did the same. When I give it gas, it idles at 1800rpm. It does not idle down until I force the TB back.
Do I need to replace TB or it could be the throttle cable???
Ok. Here is what I found out. TB sticks at partially open. It does not close 100%.
I foreced it by hand and it would idle perfect. Done this several times and it idles perfect when I force TB by hand. However, it does not go back to close by itself.
I think it is the spring or the TB blade shaft.
So, I took out the TB, removed the TPS and cleaned TB with WD40 and sprayed the shaft from both sides. Sprayed the spring. Cycled TB from close to open by hand several times.
I adjusted the TB screw out to make the blade close more.
Put it back and it did the same. When I give it gas, it idles at 1800rpm. It does not idle down until I force the TB back.
Do I need to replace TB or it could be the throttle cable???
I foreced it by hand and it would idle perfect. Done this several times and it idles perfect when I force TB by hand. However, it does not go back to close by itself.
I think it is the spring or the TB blade shaft.
So, I took out the TB, removed the TPS and cleaned TB with WD40 and sprayed the shaft from both sides. Sprayed the spring. Cycled TB from close to open by hand several times.
I adjusted the TB screw out to make the blade close more.
Put it back and it did the same. When I give it gas, it idles at 1800rpm. It does not idle down until I force the TB back.
Do I need to replace TB or it could be the throttle cable???
Thread Starter
TECH Resident
Joined: Dec 2008
Posts: 995
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Sounds like the cable may be out of adjustment. Follow the cable back away from the throttle body, and you should find a small square piece in the cable. That's an adjuster. You pop the plastic U shaped piece off it, and you can lengthen or shorten the cable some. Then snap the piece back on it and you're done. 2 minute job.
I sprayed it with WD40 and flipped the throttle several times by the gas pedal and I could hear the TB close 100%.
Put back the cover and started the car. Now it idles perfect even after pressing the gas and letting it idle. It's back to normal.
I did not adjust the cable at all.
It turned out there was dust under the gear prevent it to go back fully after depressing the gas pedal.
Thanks again edcmat-l1, you saved my day.
Some little thinking could help.
Last edited by Denali08; Aug 13, 2011 at 11:54 AM.
