Starving for something when opening up throttle

[Jb14]

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

 

[BRIANGEE]

It's only at WOT?

I would:

1-check for codes for direction.

2-Check your fuel pressure at a variety of rpms - especially a full throttle snap to see how far it dips.

3-Check your O2's at WOT. Your fuel trims are probably going to a full rich command and you want to see if your O2's are detecting the results of that.

4-Do you know if your year of expy has the fuel damper or a fuel pressure regulator on the rail? They look almost identical but if you have a fuel pressure regulator you could check that as well since it's pretty simple - but you'll need a fuel pressure test kit for this and #2.

 

[Jb14]

Thank you Braingee for the reply.

WOT: Mostly yes, but the odd part is that when going WOT say gradually it studders/chokes/starves then it get past certain points then it may stop those symptoms, but usually not at the same point, then other times when I have to put it to the floor it drops gear and takes off without issue (But that is rare). The truck is great but with this many miles, I try to drive appropriately so, unfortunately, I can't give exact RPM's and speeds as I try to keep from breaking something, though I am looking into eventually rebuilding or getting remanufacture engine.

I have had the truck in the shop just last week and no codes came up

I do not know if I have a fuel damper or pressure regulator I will research that and try the tests you recommend

 

[BRIANGEE]

I was asking if it was at WOT because if it was anywhere in between I would think the throttle position sensor could be suspect too. Especially if you notice it during a certain area of gas pedal position. If you have a scan tool that can graph (like an Actron CP9690) you can watch the TPS and look for any dropouts in the signal. You can do this even with the motor off but the key in the ON position. A voltmeter hooked up to the TPS may not be able to capture it if it's just a small glitch but if that's all you have you can try that. If it were me next time you drive it I would pay close attention to where it acts up in the gas pedal and if you can consistently get it to act up at the same location - I would also try to note the RPM's - just don't go off a cliff trying to figure it all out LOL.

 

[BRIANGEE]

Also, if you're not sure if you have a fuel damper or pressure regulator you can take a look at the fuel rail. If you have one fuel line going to the rail, and a crossover to the other rail and then it terminates at the second rail then you have a fuel damper because it's a returnless system and the regulator is part of the pump. But if you have a return line from the other rail then you have a fuel pressure regulator at the rail and you can do some tests on it.

I would rather turn on the truck's AC and sit in the captain's chair with a scan tool and see what I can see first by monitoring TPS, fuel trims, and O2's. ;-)

 

[Jb14]

Thanks again I did have the TPS checked last week and they stated it was fine, I have to invest into another scan tool as my other went the way of the divorce (such is life) I will do some driving test to check on a pattern.

 

[1955moose]

Be sure on the tps, sometimes they can test OK at 0 throttle and tip in but have a jumpy reading at or near wot. Like Brian stated fuel trim all the way up the band needs checking. Also I couldn't keep up but are their any lean conditions, or codes. Anything that leans mixture will affect acceleration all the way to wot. You might want to remove throttle body, and thoroughly clean it, and install new gaskets. The smallest thing can affect acceleration. Think of these as a sophisticated carburetor. It's got to be jetted right and all must be clean and clear.

Sent from my N9131 using Tapatalk

 

[KC1903]

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.

 

[1955moose]

Scoot, that's a serious looking woofer. Be sure you mount the sub amp in an area that well ventilated. Sub amps burn out easily. Ideally if your amp doesn't have a built in fan, installing one nearby, will greatly increase its life. Most people mount an amp under a seat, or in the hole of pinole, crank the hell out of it, especially in 90 degree plus weather, and wonder why it died in less than a year or so. All the top amp brands have fans, and type D circuitry to run a little cooler. Amps and speakers that last, run cooler. With speakers, its ferro fluid on tweeters, with mids, and big woofers, they use a venting system on the pole that the woofer slides on. Woofers push air, and with high amplifier power generate heat. Let us know how your combo works out, maybe another member is thinking the same setup.

Sent from my N9131 using Tapatalk

 

[Jb14]

Be sure on the tps, sometimes they can test OK at 0 throttle and tip in but have a jumpy reading at or near wot. Like Brian stated fuel trim all the way up the band needs checking. Also I couldn't keep up but are their any lean conditions, or codes. Anything that leans mixture will affect acceleration all the way to wot. You might want to remove throttle body, and thoroughly clean it, and install new gaskets. The smallest thing can affect acceleration. Think of these as a sophisticated carburetor. It's got to be jetted right and all must be clean and clear.

Sent from my N9131 using Tapatalk

Thank you that is great insight I dod not know exactly how they tested but I will ask also I clean the throttle body every few months so should be clean. I will have them test all the way through the system

 

[Jb14]

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.

 

[Jb14]

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

 

[KC1903]

I order this one based upon others having good access.

https://www.amazon.com/gp/product/B0053OBM1Y/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

 

[Password]

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.

 

[BlueStangGT]

Does your '05 still have the original fuel pump? If not, when was it replaced?

 

[Jb14]

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

 

[Jb14]

Does your '05 still have the original fuel pump? If not, when was it replaced?

Still the original and not sure if the mechanic checked last week will need to ask

 

[BlueStangGT]

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]

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]

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.