Cold Morning Lion roar to life nothing but a kitty (1 Viewer)

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My vehicle no longer has that cold morning roar to life with the gradual RPM reduction back to idle.
Startups are at just below idle with a gradual reduction to below idle.

I've changed out the throttle position sensor and adjusted it properly. It's not that. The old TPS was working perfectly fine too. Now I have two!

I'm moving down the line for possible causes.

1- What is this?
2- How does it work??
3- How do I easily check if it's working properly without tearing into anything???
4- How long would it take to replace myself (roughly) ????

PXL_20220917_172623443_2.jpg


Thanks....
 
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What does it do?
How does it operate?
 
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That's why
Look at the SFI section of the factory service manual.
Did you look at that section? I don't see it answering the last couple questions I posted.
Please offer more if you understand it differently than I do.

I've read that section many times before I posted up.

That section does not address basic questions about the dashpot:

What does it do?
How does it operate?
 

baldilocks

Battle Ground, WA
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The dash pot has nothing to do with your problem. It’s only there to keep the throttle valve from closing too rapidly when your foot is lifted quickly and completely from the accelerator pedal, and also keeps the throttle cracked open when the engine is shut down. This part has been discontinued by Toyota which means there are many vehicles out there operating just fine without it performing it’s intended function.

Pertinent info to provide here would be: year of vehicle, maintenance that may have been done just prior to the problem you are reporting. Did the engine compartment happen to become wet not long before this all began?
 
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Did you look at that section?

Yes.

I don't see it answering the last couple questions I posted.
Please offer more if you understand it differently than I do.

Did you look at the complex diagram showing the interaction of all the SFI components, with all the vacuum lines?



A dashpot, also known as a damper, is a mechanical device that resists motion via viscous friction.[1] The resulting force is proportional to the velocity, but acts in the opposite direction,[2] slowing the motion and absorbing energy. It is commonly used in conjunction with a spring.
 
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94 (also noted in my signature). Signature cannot be seen when viewing the thread from a phone.

Okay. Understood about the dashpot. Makes sense.

Nothing wet at all. It sat for a good long while in my garage. It sat for about 6 months in my garage (it was driven around the block once a week on average). Brought it out of hibernation 3 months ago and started driving it daily.
Prior to hibernation, the head gasket was replaced. Working fine before placing in hibernation.

Was running fine for two months after I took out of hibernation, but
it's been missing the cold morning roar for about 1 month now. Runs fine at freeway speed.
Acceleration from stop is slow and hesitant. Idle is the issue or part of the issue.
 

baldilocks

Battle Ground, WA
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Have you tested/inspected the idle air controller?
 
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Have you tested/inspected the idle air controller?
Thanks baldilocks!

I've not tested or inspected the idle air controller.' l'll have to dive in and research the idle air controller.

Separately, in general, which mechanisms allow for the high idle (fan roar) at cold startup? Subsequently what mechanisms allow for the idle to back down as the engine warms up.

I ask because I don't recall these details anymore, and trying not to chase down dead end paths as I've done with this vehicle so many times before. Trying to narrow down any possible deadends with more information to digest.

Thanks. I'll check out the idle air controller.
 

baldilocks

Battle Ground, WA
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Ultimately, the engine ecu controls the idle but since you report lack luster acceleration also, and the VAFM is a common culprit in these sort of issues, I’d look into that as well.
 
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What is the problem besides the loss of start up "roar" on a cold engine,
just slow acceleration??

Can you define the "slow acceleration" in more detail?

How does it run once you're up to 30, 50, 70 mph??

Does it accelerate better once the engine is warmed up??

The roar IME is from the fan clutch engaging then free-wheeling after a minute plus or minus, but that wouldn't affect acceleration.

As mentioned above check all the simple things first, especially if it ran normally before you stopped driving it six months ago.

Have you burned through the old gasoline yet?
Did you store the vehicle with any gas stabilizer in the tank?
Have you added new gasoline or a fuel injector cleaner/water absorber
into the tank yet?
Have you checked the PCV hose, breather hose, large air intake tube for leaks and tight connections??
Is the air filter new, OEM, or??

At any point during it's storage did you fiddle/touch/repair/service/clean anything under the hood?

WARNING: don't touch any screws on your VAFM unit, there is nothing inside that is servicable. Loosening the screws will damage the unit


VAF screws.JPG
 
Last edited:
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Ultimately, the engine ecu controls the idle but since you report lack luster acceleration also, and the VAFM is a common culprit in these sort of issues, I’d look into that as well.
I'll start with the low hanging fruit first I've not thought of. The Idle Air Controller is pretty low hanging.
Thanks again.

What is the problem besides the loss of start up "roar" on a cold engine,
just slow acceleration??

Can you define the "slow acceleration" in more detail?

How does it run once you're up to 30, 50, 70 mph??

Does it accelerate better once the engine is warmed up??

The roar IME is from the fan clutch engaging then free-wheeling after a minute plus or minus, but that wouldn't affect acceleration.

As mentioned above check all the simple things first, especially if it ran normally before you stopped driving it six months ago.

Have you burned through the old gasoline yet?
Did you store the vehicle with any gas stabilizer in the tank?
Have you added new gasoline or a fuel injector cleaner/water absorber
into the tank yet?
Have you checked the PCV hose, breather hose, large air intake tube for leaks and tight connections??
Is the air filter new, OEM, or??

At any point during it's storage did you fiddle/touch/repair/service/clean anything under the hood?

WARNING: don't touch any screws on your VAFM unit, there is nothing inside that is servicable. Loosening the screws will damage the unit


View attachment 3118268

Acceleration from a stop is hesitant but it will accelerate. I have to keep my foot on the gas at stops to keep the engine idling high enough to keep from stalling. I lift my foot off the pedal it may stall.

Highway speeds and accelerations on the highway are not problem. Once I get it up and going from a stop the vehicle functions normally.
Went through a few tanks of good gas. Maybe 4-5 full tanks before this weirdness started. Fuel filter replaced and fuel pump replaced after all this stuff happened.

"Yes" to all this low hanging fruit and more...:
"Have you checked the PCV hose, breather hose, large air intake tube for leaks and tight connections??
Is the air filter new, OEM, or??"

It won't hold idle properly. I have to keep my foot on the pedal to keep a normal idle at stops, else it quits.
I don't want to go the shotgun cash drain approach. I'll start with the IAC first.

Thanks.
 

ChaseTruck

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Maybe check this out:


That helped with our '93
 

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