Please help! Low idle!
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7th Gear
Joined: Feb 2025
Posts: 7
Likes: 1
Please help! Low idle!
I have an 08 King Ranch, I've been having trouble with low idle speeds to a point where it almost seems like it wants to stall out when I'm at a red light. When it's in park/neutral it idles just fine, but when it's in drive or reverse it idles abnormally low to where it wants to stall but it doesn't stall out, it idles around 450-500 and vibrates the whole cab. I have done a relearn on a throttle body and it fixed it for about 10 minutes but now it's doing the same thing. Does anyone have any ideas that could help me track down the problem? I'm debating on buying an Edge Evolution so I can adjust the idle RPMs but I do not want to pay the 400 dollars for that, but if it comes to it I will.
More Turbo
Joined: Oct 2023
Posts: 607
Likes: 153
From: Canada
Can you access and test the manifold actuator and did you also replace the lower intake manifold Gaskets? I would rediagnose the manifold for leaks. Check the air arm for cracks. And maybe order a smoke machine for like 75 bucks and get a bottle of mineral oil. There is also an idle air control valve in there I believe.
also as far as the job its for experienced techs. And mistakes can be made. Simply upping the idle won't solve the issue. Just mask it. Those lower intakes warp. And if you torque it wrong it warps.
also as far as the job its for experienced techs. And mistakes can be made. Simply upping the idle won't solve the issue. Just mask it. Those lower intakes warp. And if you torque it wrong it warps.
Fleet Mechanic
Joined: Jul 2019
Posts: 1,307
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Sounds like you did a timing job to some extent, but still have low oil pressure. That would not be good.
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7th Gear
Joined: Feb 2025
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Yes I had the motor sent off to do the timing and I had them put in the millings high preassure oil pump. I ended up replacing all the gaskets and seals got a new intake and exhaust manifolds. Basically replaced everything to ensure that I wouldn’t have problems. The truck is pushing 300k miles so Ive been thinking it could be something in the computer
Fleet Mechanic
Joined: Apr 2016
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Making a diy smoke machine off you tube solved my problem . Far better way to look for leaks . I would assume its a 5.4l which does not have an idle air control . The pcm just opens the butterfly in throttle body a small amount to provide idle air so clean that throttle body real good with the special cleaner and a tooth brush . . You can put a rubber glove on throttle body mouth to stop smoke from escaping , look at your gaskets around air filter . check for nests in air supply .
Also do a mode six test for misfires by cly ,it will tell you raw computer counts towards setting a code . The theshold is quite high , you want zero counts .
Also do a mode six test for misfires by cly ,it will tell you raw computer counts towards setting a code . The theshold is quite high , you want zero counts .
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7th Gear
Joined: Feb 2025
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Making a diy smoke machine off you tube solved my problem . Far better way to look for leaks . I would assume its a 5.4l which does not have an idle air control . The pcm just opens the butterfly in throttle body a small amount to provide idle air so clean that throttle body real good with the special cleaner and a tooth brush . . You can put a rubber glove on throttle body mouth to stop smoke from escaping , look at your gaskets around air filter . check for nests in air supply .
Also do a mode six test for misfires by cly ,it will tell you raw computer counts towards setting a code . The theshold is quite high , you want zero counts .
Also do a mode six test for misfires by cly ,it will tell you raw computer counts towards setting a code . The theshold is quite high , you want zero counts .
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7th Gear
Joined: Feb 2025
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yes same throttle body
Fleet Mechanic
Joined: Dec 2003
Posts: 1,436
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From: Virginia
Hmmm... I've been known to bark up the wrong tree before, but you need to narrow down what is "common" between the old & new motors.
IE - if items were reused like VCT, PCM, TB, etc...
The TB is completely electronically controlled, the little motor that takes signals from the computer & adjusts based on conditions may have seen better days.
Cleaning the TB like you did may only smooth things out a little but won't correct faulty positioning.
If it isn't the TB then I am back to "what other items were on the old motor?"
IE - if items were reused like VCT, PCM, TB, etc...
The TB is completely electronically controlled, the little motor that takes signals from the computer & adjusts based on conditions may have seen better days.
Cleaning the TB like you did may only smooth things out a little but won't correct faulty positioning.
If it isn't the TB then I am back to "what other items were on the old motor?"
Thread Starter
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7th Gear
Joined: Feb 2025
Posts: 7
Likes: 1
Hmmm... I've been known to bark up the wrong tree before, but you need to narrow down what is "common" between the old & new motors.
IE - if items were reused like VCT, PCM, TB, etc...
The TB is completely electronically controlled, the little motor that takes signals from the computer & adjusts based on conditions may have seen better days.
Cleaning the TB like you did may only smooth things out a little but won't correct faulty positioning.
If it isn't the TB then I am back to "what other items were on the old motor?"
IE - if items were reused like VCT, PCM, TB, etc...
The TB is completely electronically controlled, the little motor that takes signals from the computer & adjusts based on conditions may have seen better days.
Cleaning the TB like you did may only smooth things out a little but won't correct faulty positioning.
If it isn't the TB then I am back to "what other items were on the old motor?"
also ask any questions needed I’m just trying to fix this problem.
I did do a throttle relearn and it seems to be a little better but still low idle
Last edited by ghuffman; Feb 27, 2025 at 01:54 PM.
More Turbo
Joined: Oct 2023
Posts: 607
Likes: 153
From: Canada
If it's not an air leak. And the sensors are good. It good be related to the timing assembly. But if you replaced all that stuff too in out of ideas. But you are right that the ECU is old enough to have failing capacitors. And a blown capacitor on the board could in fact screw up idle and things like warm up idle and fuel pump priming and stuff. I'm not overly familiar with 5.4 But the other issue I've had on vehicles with odd idle issues were cured by replacing the braided ground strap and battery cables and cleaning the grounds. This was on the digifant used in the 80 and 90s by VW.
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7th Gear
Joined: Feb 2025
Posts: 7
Likes: 1
If it's not an air leak. And the sensors are good. It good be related to the timing assembly. But if you replaced all that stuff too in out of ideas. But you are right that the ECU is old enough to have failing capacitors. And a blown capacitor on the board could in fact screw up idle and things like warm up idle and fuel pump priming and stuff. I'm not overly familiar with 5.4 But the other issue I've had on vehicles with odd idle issues were cured by replacing the braided ground strap and battery cables and cleaning the grounds. This was on the digifant used in the 80 and 90s by VW.
More Turbo
Joined: Oct 2023
Posts: 607
Likes: 153
From: Canada
The only other time I've had strange low idle was a custom install of an ECU into a different car. The manifold was using spacers and stuff. I had to add a ground strap right to the manifold itself to get the computer to work properly. And I have been shown in class once a braided strap that looks fine but was full of internal resistance. Aside from that. I'm basically out of ideas. Other than find the book with the values for all the sensors and actuators. And see if they're in ideal range. But that's last ditch stuff. Testing resistances and doing sweep tests. If you see me doing a wiggle test. I'm out of ideas.