Idling too high
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Junior User
Joined: Jul 2017
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Idling too high
hi guys. I’m hoping for some advice here. I recently rebuilt a 460 and I’ve worked out most of the bugs but I’ve got one left. It seems to be idling really high. I took apart everything and cleaned and reused a lot of the old parts. I’m thinking that I need to recalibrate the tps but I’m not sure how about doing that. Or if that’s possible for my engine. I completely cleaned out the throttle body and it isn’t catching or anything. Tranny was rebuilt by a reputable shop. All new vacuum lines. I went through them and I don’t have any leaks. Thoughts?.. thanks
1990 460 bored 30 over efi e4od
1990 460 bored 30 over efi e4od
First rebuild ever
Cargo Master
Joined: Jun 2013
Posts: 3,182
Likes: 15
From: Somewhere n North America
Even though you have replaced all the Vacuum Lines does not prove no vacuum leak, the Devices the lines connect to can be suspect for leaks.
To prove this, you can cap/plug all vacuum lines except for the MAP & Fuel Pressure Regulator (FPR).
Many times, newly rebuilt engines have shifted intake gaskets during install.
Injectors can be a source of vacuum leaks as well if not seated properly or if the Injector Seals are not tight.
Throttle body valve Plate and Shaft wear/deformity can cause additional unmetered air flow, as well as a misadjusted Throttle Plate Stop Screw.
You can measure the voltage output from your TPS on the Dark Green/Light Green striped wire, this voltage should be less than 1 vdc at Closed Throttle.
Did you replace your EGR-Valve?
What happens when you disconnect the connector to your Air Bypass Valve?
To prove this, you can cap/plug all vacuum lines except for the MAP & Fuel Pressure Regulator (FPR).
Many times, newly rebuilt engines have shifted intake gaskets during install.
Injectors can be a source of vacuum leaks as well if not seated properly or if the Injector Seals are not tight.
Throttle body valve Plate and Shaft wear/deformity can cause additional unmetered air flow, as well as a misadjusted Throttle Plate Stop Screw.
You can measure the voltage output from your TPS on the Dark Green/Light Green striped wire, this voltage should be less than 1 vdc at Closed Throttle.
Did you replace your EGR-Valve?
What happens when you disconnect the connector to your Air Bypass Valve?
Mountain Pass
Joined: Jun 2013
Posts: 113
Likes: 0
Even though you have replaced all the Vacuum Lines does not prove no vacuum leak, the Devices the lines connect to can be suspect for leaks.
To prove this, you can cap/plug all vacuum lines except for the MAP & Fuel Pressure Regulator (FPR).
Many times, newly rebuilt engines have shifted intake gaskets during install.
Injectors can be a source of vacuum leaks as well if not seated properly or if the Injector Seals are not tight.
Throttle body valve Plate and Shaft wear/deformity can cause additional unmetered air flow, as well as a misadjusted Throttle Plate Stop Screw.
You can measure the voltage output from your TPS on the Dark Green/Light Green striped wire, this voltage should be less than 1 vdc at Closed Throttle.
Did you replace your EGR-Valve?
What happens when you disconnect the connector to your Air Bypass Valve?
To prove this, you can cap/plug all vacuum lines except for the MAP & Fuel Pressure Regulator (FPR).
Many times, newly rebuilt engines have shifted intake gaskets during install.
Injectors can be a source of vacuum leaks as well if not seated properly or if the Injector Seals are not tight.
Throttle body valve Plate and Shaft wear/deformity can cause additional unmetered air flow, as well as a misadjusted Throttle Plate Stop Screw.
You can measure the voltage output from your TPS on the Dark Green/Light Green striped wire, this voltage should be less than 1 vdc at Closed Throttle.
Did you replace your EGR-Valve?
What happens when you disconnect the connector to your Air Bypass Valve?
Cargo Master
Joined: Jun 2013
Posts: 3,182
Likes: 15
From: Somewhere n North America
Funny you mention this. I posted something similar a few months back, but the guy didn't initially include the Speed Control, PCV- Valve, HVAC & the Brake Booster vacuum lines in his Cap-off/Plug vacuum test.
So, 2 months later, he determines he has a vacuum leak in his Speed Control Diaphragm, because he never capped it off.
Now, in his defence, he acknowledged that he is not a seasoned shade tree mechanic.....
So, I think I will make an itemized list in the future of what I would recommend be capped or plugged for a test.....
So, 2 months later, he determines he has a vacuum leak in his Speed Control Diaphragm, because he never capped it off.
Now, in his defence, he acknowledged that he is not a seasoned shade tree mechanic.....
So, I think I will make an itemized list in the future of what I would recommend be capped or plugged for a test.....
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