07 Expy low torque/acceleration (no other symptoms)

[Zigwaldo]

Hi All,

I’ve been fighting with this on and off (not my daily so doesn’t get my constant attention) since I got this rig a couple years ago. I’ve scoured the interwebs (including this forum) and haven’t seen anything that directly aligns with what I’m experiencing.

No CEL, and no supporting symptoms (noises, stuttering or sputtering, vibrations, difference in cold start vs operating temp, smells like bad cats or running rich). I know these aren’t going to run 10’s in the 1/4, but this is exceptionally piggish. Best way I can describe it is it’s almost like there’s an air or fuel restriction, but I can’t track down any evidence of either…

It’s got 165k miles and I don’t know how it was maintained previously, so I’ve replaced a couple things chasing this down just for good measure (TL;DR it was free.99, so wasn’t exactly picky). Mostly got it to have a 4x4 to take camping, fishing, find some snow. But it can’t make it up the 6-12% grades to get to the good spots…

- spark plugs (had autolite, didn’t look fouled or saturated. Replaced with the updated motorcraft)
- coils (MSD Blasters)
- upstream 02 sensors (since they can be out of range without a code)
- fuel filter
- air filter

I’ve also attempted some “free” fixes
- cleaned MAF
- cleaned TB
- couple rounds of Lucas fuel injector cleaner
- marvel in the gas tank
- PCM reset w/ full drive cycle

I have the ability to view some live data, but not sure what normal values should be so if anyone has any baselines that would be very helpful. It’s my first 5.4 3v so if anyone has any other ideas on what to look at, that’s what I’m really after. Don’t have a shop I trust so really don’t feel like doing that dance to have someone else diagnose, but that’s about where I’m at unfortunately.

 

[GlennSullivan]

Have you considered plugged Cats?

 

[Zigwaldo]

Is there a good way to test that? There’s no egg or sulfur smells, and temps look to be within range.

 

[GlennSullivan]

Is there a good way to test that? There’s no egg or sulfur smells, and temps look to be within range.

If you can put your hands on a digital infrared thermometer, take a 10 minute ride in the vehicle, then check the exhaust pipe temps before and after the cats, they should be close before and after and left to right. If one side is much hotter before than after, that would indicate that cat is not flowing correctly.

 

[Zigwaldo]

Thanks! I will give that a try and report back.

 

[GlennSullivan]

Considering all the things you have already preemptively addressed, the only other things that come to mind are throttle body and fuel pump / pickup, both of which should throw codes, but Ive seen each not perform as expected and not throw codes - fuel pump in Mustang and TB in Expedition.

 

[Zigwaldo]

If you can put your hands on a digital infrared thermometer, take a 10 minute ride in the vehicle, then check the exhaust pipe temps before and after the cats, they should be close before and after and left to right. If one side is much hotter before than after, that would indicate that cat is not flowing correctly.

Got to this yesterday, temps were +\- 20 degrees before and after on either side.

 

[Zigwaldo]

Considering all the things you have already preemptively addressed, the only other things that come to mind are throttle body and fuel pump / pickup, both of which should throw codes, but Ive seen each not perform as expected and not throw codes - fuel pump in Mustang and TB in Expedition.

Thanks, I’ve found the pinouts and will check voltage and resistance on the TPS and motor. For the fuel pump, that seems like a PITA to test the pressure w/o a schrader valve, or to get to the fuel pump itself to test it. Probably hold off on that for now unless it develops a behavior that makes it more likely.

I appreciate the suggestions and insight. With the exception of electrical, this is definitely one of the weirder issues I’ve had to try and track down.

 

[biscayne]

My 09 acted like this and I was told the timing wasn't advancing properly due to oil pressure insufficient at the phasers.

 

[BOB4254]

My 1998 Exp 5.4L, will accelerate to 2000 RPM. Then when I floor it engine bog's down. When I let up on the gas pedal half way, engine accelerates and takes off as long as I keep her around 2000 RPM. No miss firers. New plugs, coils and wires. Cleaned and checked fuel injectors for proper operation. Cleaned MAF. Getting Codes P0171 & P0174. 1998 Ford Expedition 5.4L, 130k miles.

I installed a new Bosch fuel pump in the original fuel pump assembly which solved the no acceleration issue.

She runs like the day I bought her brand new in 1998.

I did not install a new fuel filter as I installed a new fuel filter four weeks ago.

When Mechanical fuel pumps fail, they only fail, car will not start.

Electric fuel pumps can become weak before they fail not supplying the fuel your 5.4L needs to accelerate.

Weak = not able to supply the fuel required for acceleration.

Amazon.com

 

[GlennSullivan]

Thanks, I’ve found the pinouts and will check voltage and resistance on the TPS and motor. For the fuel pump, that seems like a PITA to test the pressure w/o a schrader valve, or to get to the fuel pump itself to test it. Probably hold off on that for now unless it develops a behavior that makes it more likely.

I appreciate the suggestions and insight. With the exception of electrical, this is definitely one of the weirder issues I’ve had to try and track down.

Are you sure there is no Schrader Valve on either fuel rail? Have you connected an ODBII reader yet to see if any codes?

 

[Zigwaldo]

I was wrong on the valve, and no codes (kinda wish there was…). I was also able to get some more info from the previous owner and purportedly the fuel pump was replaced around 20k miles ago.

Looking to see if there’s a way to read pressure through OBD at speed, I did stumble across this. Mine’s not subject to the recall mentioned, but, that would make a hell of a lot sense given everything else that’s been eliminated.

Help finding fuel pressure sensor

I'm trying to locate the fuel injection pressure sensor on my 08 Expedition. I bought the sensor, but can't find where it's mounted. Normally they would be mounted on the injection rail. Mine however just looks like the injectors are the only thing on the rail. This sensor probably wont fix my...

www.expeditionforum.com

Has anyone else had similar results after flashing a tune? Factory or otherwise.

 

[Zigwaldo]

I was also able to grab a quick crappy video. This is rolling at 30mph then flooring it.

November 14, 2024

youtube.com

 

[GlennSullivan]

From I understand, you should be able to live monitor fuel pressure with the ForScan App by setting the correct PID and although I own ForScan I have not used it for this purpose. You can ask that question in the dedicated ForScan section of this site or perhaps someone more knowledgeable with the app can post it here.

 

[max78]

Some of these trucks have foam in the fender that get sucked onto the snorkel of the airbox while running, My truck had the foam, but it was still in place but I removed it anyways.

Here is a video about it.
https://www.youtube.com/watch?v=0NOI6JBByhs

I had some very similar issues. No power, felt like it was pulling a heavy trailer all the time, no codes. New fuel pump, filter, plugs, and a ton of engine related stuff that was due for replacement for other reasons. None of it really made a huge difference and it was still sluggish.

What I found in my case was my brake booster was bad. . . . Here is my thread if you want to check it out. https://www.expeditionforum.com/threads/09-3v-power-loss-cured-with-5w40.54650/

In short I found my brake booster had failed and the brakes were dragging, but not enough to be obvious. An easy test is to see if you vehicle coasts on flat or even downhill, my truck would slow down even when going down a slight grade.

To further test this you can jack up the front and spin the tires by hand, if its 4x4 you can start the car so the hubs disengage because they automatically engage when vacuum is lost.

Other things to consider, from the factory these have torque control. If the transmission seems to be unhappy because some "parameters" are not quite right it will kill torque and acceleration so the transmission doesn't die, this does not always cause a code. There were a few threads I read where a trans rebuild solved a lack of acceleration.

 

[Zigwaldo]

Wanted to provide a (final!) update.

I used a more advanced scan tool to view the live data, and noticed the throttle position values were out of spec (68% on WOT). Swapped the TPS, had a crank no start… With the high miles, just decided to pick up a motocraft TB assembly that came with the TPS and actuator, drained the capacitors in the ECM and did a re-learn. Runs like a whole new truck.

December 5, 2024

youtube.com

Thank you to everyone for all the replies and suggestions!

 

[GlennSullivan]

And thank you for following up with the solution.
Interesting, I thought 15-17 were the only ones with bad throttle body issues.