Starving for something when opening up throttle

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Jb14

Jb14

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I have this same symptoms on my truck with 230k and i’ll Know for certain if my own diagnosis is correct.

The throttle body is electronically controlled with a motor gear to a gear on the throttle body butterfly, non-serviceable so you have to replace the entire throttle body. As the truck has been driven since day 1, that initial tip of the throttle is used the most frequently and is the hardest on the gearing - in that the the motor is closed off by the throttle body and starved for air. The motor is a huge air pump and it wants to draw in air, throttle body being closed prevents that draw. I suspect that over time the gears are worn to the point that there is too much play in the gearing and the butterfly can actually chatter in place when near closed. The stumble we experience is a delay in opening followed by immediate chatter caused by open/close due to loose tolerances in the gearing, now air to fuel ratio is off at a critical moment which is a moment of “accelerate” not a moment of “maintain” rpm. The loose gearing leaves us at a point where TPS and Air/Fuel ratios go psychotic until the butterfly opens enough and the gear tolerances become solid again that the ECm can actually use the sensors to manage the air/fuel ratio.

Downshifting the O/D nets a similar situation by resulting in a more open butterfly and the motor smooths out instantly.

My new throttle body gets installed next weekend.
As you described make sense and from your description is exactly how it feels like it is behaving really appreciate you responding.
 
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Jb14

Jb14

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I have this same symptoms on my truck with 230k and i’ll Know for certain if my own diagnosis is correct.

The throttle body is electronically controlled with a motor gear to a gear on the throttle body butterfly, non-serviceable so you have to replace the entire throttle body. As the truck has been driven since day 1, that initial tip of the throttle is used the most frequently and is the hardest on the gearing - in that the the motor is closed off by the throttle body and starved for air. The motor is a huge air pump and it wants to draw in air, throttle body being closed prevents that draw. I suspect that over time the gears are worn to the point that there is too much play in the gearing and the butterfly can actually chatter in place when near closed. The stumble we experience is a delay in opening followed by immediate chatter caused by open/close due to loose tolerances in the gearing, now air to fuel ratio is off at a critical moment which is a moment of “accelerate” not a moment of “maintain” rpm. The loose gearing leaves us at a point where TPS and Air/Fuel ratios go psychotic until the butterfly opens enough and the gear tolerances become solid again that the ECm can actually use the sensors to manage the air/fuel ratio.

Downshifting the O/D nets a similar situation by resulting in a more open butterfly and the motor smooths out instantly.

My new throttle body gets installed next weekend.
I should have asked in the previous response our trucks can be picky when it comes to parts and in a lot of cases OEM is the only thing that works. You stated that you're waiting on your throttle body to come in did you go OEM or aftermarket? If aftermarket how did you get to that choice?

Also welcome to the forum and thank you for your contribution
 

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I am needing guidance if possible before I take my truck to a mechanic. I have a 2005 5.4 3V with 276K (great truck) I have had an issue for a while that when I get into the gas as in needing full throttle the engine feels like its starving for gas, air, spark not exactly sure what. It is not fully cutting out just stumbles in and out of power so hard to define. All the maintenance is up to date, COPs, Plugs, gas & air filter, MASS clean and so on.

I stated that the symptom has been going on for a while as I drive fairly easily and at regular spirited driving I have no issue and runs great. The truck is still running with the equipment it was manufactured with minus a couple batteries and trans works, and I did replace the VVT solenoids. I do have the ticking a bit but idles smooth and runs smoothly unless getting into gas at top end as described.

Thanks in advance
I know you say the COP's are up to date, but it might not hurt to make sure one is not faulty. The only time I have experienced your symptoms was from bad COP's.
 
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Jb14

Jb14

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I know you say the COP's are up to date, but it might not hurt to make sure one is not faulty. The only time I have experienced your symptoms was from bad COP's.
Thanks I had them checked when truck was in the shop last week and all good
 

BlueStangGT

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Still the original and not sure if the mechanic checked last week will need to ask
I had to have mine replaced on my 05 2WD at about 60k and on my 07 4WD around 110k. My 05 started exhibiting symptoms similar to those you describe, it took awhile to track down the culprit. My '07 was just dead one morning... it would spin but no fire.
 

1955moose

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Sadly like our hearts, fuel pressure readings like blood pressure is one of the few tests. Even though they have a protective screen, debris gets through. Along with that wires are submerged in fuel, and break down in time. Have your shop check fuel pump readings like Brian stated, not just at idle but all the way up to wot. If it drops below 33 at any point, the pump may be your problem. Also have them check or better still replace fuel pump driver module, mounted near your spare tire. They corrode and cause various driveability problems. Let us know what they find.

Sent from my N9131 using Tapatalk
 

KC1903

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As you described make sense and from your description is exactly how it feels like it is behaving really appreciate you responding.
It worked.

- no more stumble at throttle tip in
- motor is far more response with freeway on ramps, as in more power to get the job done

Make certain that you disconnect the battery, reconnect, turn key on and watch dash light calm themselves, then start and let it idle for 15 to 20 minutes as the computer relearns

It will be interesting to see if fuel mileage improves.

Spirited driving is much more enjoyable.

The kit I referenced early included the gasket for between the TB and the manifold, 20 ~ 30 minute job to install 10mm deep socket for the eight bolts and 8mm for the battery terminal.
 

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