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Discussion Starter · #1 · (Edited)
This morning I started my truck, truck shook more than usual. I have a built motor and it normally shakes a bit upon startup, but this time it shook bad. Rpms fluctuating up and down.

Also showing no Boost on our factory boost gauge or on my aftermarket digital gauge.

Also noticed a loud humming yesterday driving home, and when I started it this morning, there was still a loud humming sound which sounds like the SC being under a constant low load.

I went to drive it think morning, loud humming at start & at red lights. Above 30/40 mph I let off the gas and it feels like it’s in cruise control when it’s not, it doesn’t lose speed a lot once I take my foot off the pedal and it coasts around said mph when I take my foot off the pedal.

it still has its power and I can still hear the whine of the SC on WOT. What could it be? Bad IAC? Boost actuator?
 

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Wile E. Coyote, Super Genius!
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The IAC on Lightning's unlike other vehicles, when it's bad, it makes a sound more akin to a cow mooing. Easiest way to tell if it's good or bad, is simply disconnect the plug while the truck is idling. Idle should get real low, or the truck should stall. Either is indicative that it's still working. I've had to replace mine twice since I bought it in late 2009. First time was in 2013. I used an El Cheapo Auto Zone part, lasted about a month. Replaced it with same and t lasted until 2019. At that time, I saw on Auto Zones computer they have a "Premium" part. I inquired about it, and was told it's a Hitachi from Japan. Went with that, good so far.

The IAS isn't going to affect boost, far as I know.

Boost Bypass valve should be down, resting on the lower flange of the blower. When you start the truck, it should pull to the up position. A spring holds it down, vacuum pulls it up. On mine, if I give the throttle a good twist while idling, I can watch it drop down very briefly before going back up again.

My Mustang just had the problem with the feeling like it was on cruise when I lifted my foot. No engine braking at all. Transmission went out, OD OFF light blinking. Second time, it was rebuilt in April. It's a known POS. We are going to yank the auto and replace it with a stick.
 
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Discussion Starter · #3 ·
The IAC on Lightning's unlike other vehicles, when it's bad, it makes a sound more akin to a cow mooing. Easiest way to tell if it's good or bad, is simply disconnect the plug while the truck is idling. Idle should get real low, or the truck should stall. Either is indicative that it's still working. I've had to replace mine twice since I bought it in late 2009. First time was in 2013. I used an El Cheapo Auto Zone part, lasted about a month. Replaced it with same and t lasted until 2019. At that time, I saw on Auto Zones computer they have a "Premium" part. I inquired about it, and was told it's a Hitachi from Japan. Went with that, good so far.

The IAS isn't going to affect boost, far as I know.

Boost Bypass valve should be down, resting on the lower flange of the blower. When you start the truck, it should pull to the up position. A spring holds it down, vacuum pulls it up. On mine, if I give the throttle a good twist while idling, I can watch it drop down very briefly before going back up again.

My Mustang just had the problem with the feeling like it was on cruise when I lifted my foot. No engine braking at all. Transmission went out, OD OFF light blinking. Second time, it was rebuilt in April. It's a known POS. We are going to yank the auto and replace it with a stick.
Hopefully it’s the boost bypass then! I’m hoping lol.. sometimes those premium Japanese parts work great! The truck feels like it’s on cruise when I lift my foot as well. Also, the od light would Flash on and off a while back, hasn’t done that flashing for a while lately Though. Would that be related to the boost bypass or iac? I need to check out the boost bypass once I get home.
 

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Wile E. Coyote, Super Genius!
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The OD OFF blinking is not a good thing. Unfortunately it's hard to diagnose. When it blinks, you need to pull into a transmission shop or maybe Auto Zone, and have them scan it and find out the codes. Once you turn it off, trans codes go away until it blinks again. I'm fortunate in that I have a friend with a trans shop one mile away from where I live. My OD OFF light blinked intermittently for a few months last year, didn't happen every time I drove it. Code was P0741, Torque Converter Clutch Locked Off. Then WHAM, it failed in March. Got it rebuilt by said friend, and it failed again Memorial Day weekend. It's a 5R55, what Rick says is one of Ford's worst ever transmissions. We are just going to yank out the POS auto and replace it with a five speed manual, and put 4.1 gears n the axle while he has it.
 

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Discussion Starter · #5 ·
The OD OFF blinking is not a good thing. Unfortunately it's hard to diagnose. When it blinks, you need to pull into a transmission shop or maybe Auto Zone, and have them scan it and find out the codes. Once you turn it off, trans codes go away until it blinks again. I'm fortunate in that I have a friend with a trans shop one mile away from where I live. My OD OFF light blinked intermittently for a few months last year, didn't happen every time I drove it. Code was P0741, Torque Converter Clutch Locked Off. Then WHAM, it failed in March. Got it rebuilt by said friend, and it failed again Memorial Day weekend. It's a 5R55, what Rick says is one of Ford's worst ever transmissions. We are just going to yank out the POS auto and replace it with a five speed manual, and put 4.1 gears n the axle while he has it.
Well Atleast you know it’s getting done right this time!!! 😎

& as for the loud sc whistle at start and at red lights, think it’ll be the boost actuator? Gauge reads 0 boost, but it feels like I’m in cruise control at certain speeds. Should I start with the boost actuator or the IAC? I dk where to start.
 

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Wile E. Coyote, Super Genius!
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Like I said, look at the boost bypass valve running and off. If off, it's resting on the blower flange, and running, it's pulled up to the OPEN position, it's good. The Boost Bypass valve is a spring loaded vacuum diaphragm. It's spring loaded to be down, in the CLOSED position. If it's bad, it'll be CLOSED all the time, meaning the bypass port is out of use all the time. The only way I could see it being stuck in the OPEN position, UP, is if the spring in the diaphragm breaks. EGR valve is the same way, and I just removed one off my 98 Ranger that was stuck open. It's rare, but it happens. Deleting the EGR, just like I did on my Lightning.

Loud supercharger whistle, for me thus far, every time it's happened, it's been a leaking gasket between the plenum and blower. And yes, it makes starting and driving difficult. And it idles terribly. And it's LOUD!! I finally gave up on using gaskets there, because the JLP plenum doesn't like gaskets. I use black RTV on it now, and haven't had another issue since.

Same thing happens if I drain the oil out of the separator, and forget to close the petcock on the bottom. Really horrible idle, impossible to even drive it out of the garage it's so bad.
 
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Discussion Starter · #7 · (Edited)
Like I said, look at the boost bypass valve running and off. If off, it's resting on the blower flange, and running, it's pulled up to the OPEN position, it's good. The Boost Bypass valve is a spring loaded vacuum diaphragm. It's spring loaded to be down, in the CLOSED position. If it's bad, it'll be CLOSED all the time, meaning the bypass port is out of use all the time. The only way I could see it being stuck in the OPEN position, UP, is if the spring in the diaphragm breaks. EGR valve is the same way, and I just removed one off my 98 Ranger that was stuck open. It's rare, but it happens. Deleting the EGR, just like I did on my Lightning.

Loud supercharger whistle, for me thus far, every time it's happened, it's been a leaking gasket between the plenum and blower. And yes, it makes starting and driving difficult. And it idles terribly. And it's LOUD!! I finally gave up on using gaskets there, because the JLP plenum doesn't like gaskets. I use black RTV on it now, and haven't had another issue since.

Same thing happens if I drain the oil out of the separator, and forget to close the petcock on the bottom. Really horrible idle, impossible to even drive it out of the garage it's so bad.
Fixed it! I got home as a nervous wreck hoping it was something small. I traced lines and found a hose that was off! Must’ve came off yesterday! Great start up and idle now! It was this hose that was off. (The red one was off of the nipple) plugged it back in and works like a charm. Showing boost and clean idle. Going to drive around now.

* just drove around, drove awesome!!!!!
544771
544772
 

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Wile E. Coyote, Super Genius!
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Yeah, that's the one that powers the boost gauge. Vacuum leak there and it'll be real farked up. Good find.
 
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Wile E. Coyote, Super Genius!
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There is also the reason for the whistle and the no boost readings. It's a vacuum fitting, shouldn't just all off since vacuum is always pulling on it when you're off boost. I suppose that boost could blow it off. Mine's never come off. It's 17 years old.
 

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Discussion Starter · #12 ·
There is also the reason for the whistle and the no boost readings. It's a vacuum fitting, shouldn't just all off since vacuum is always pulling on it when you're off boost. I suppose that boost could blow it off. Mine's never come off. It's 17 years old.
I was punching it hard on the freeway yesterday (I don’t always do that lol), so I’m sure that’s prob why it popped off also. Thank you SO MUCH for your help! 🙌
 

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Wile E. Coyote, Super Genius!
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I was punching it hard on the freeway yesterday (I don’t always do that lol), so I’m sure that’s prob why it popped off also. Thank you SO MUCH for your help! 🙌
Never a problem. Glad you got it worked out.
 
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