Power issue 03 5.4

[Fanatic1074]

The accel cops enjoy a *very* less than stellar reputation on other forums. Might wanna try some ford ones. ($$). I remember one guy saying he ripped out the accels after stupid low miles with them. The fact that you are recording some misfires supports that also.

My only issue with that is that I had the issue before changing all of the coils and seems like everyone says something bad about each brand. Even the ford ones the dealer says they are hit and miss. I'm so close to just saying **** it and buying an armada. Why can we Americans build anything worth a crap anymore? Grrrrrr!!!

 

[Fanatic1074]

I have and 05 expy 5.4 I've was having power issues as well plus terrible gas mileage. Im not sure if this will help but I did get my issue resolved. Your symptoms sound pretty close to mine.

I had two issue one was with the MAF wiring and throttle body.

First the MAF. There was a wire that split and was touching but not completely, when I cleaned my throttle body it completely separated the wire. So in the wiring leading to the MAF the broken section got fixed and now is working perfect. But after it was fixed the truck ran worse because the throttle body was bad as well. I replaced the throttle body and now with both fixes it literally runs better that new (124K mile) my gas mileage is also great now.

One other note I had a great mechanic that was with ford for 18 years and has owned his own shop for 7 specializing in fords what thing he mentioned was with replacing the stock airbox with an after market intake. He stated that the box is designed to have the air pass the MAF in a certain way and that if its not it can send mixed signals. Not sure if true but thought Id mention it..

Good Luck

Been thinking about what you have said and i was thinking about replacing the throttle body. Can i ask what TB you replaced it with?

Also anyone know of a good after market TB, maybe that will add more HP/MPG?

 

[rockyw123]

Cats?

 

[Fanatic1074]

I have to check the back pressure in there is absolutely no pressure until I plug the exhaust hole.

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[Jb14]

The machanic replaced it with a stock throttle body. I wanted to use a higher performance brand but due to the fact that after he fixed the MAF wire it ran so bad and I lived very far from him I had not choice but stock. One thing I do notice with the new throttle body is that my RPM idle is 1500 where as before it was 1000 to 1200. With stock tires on fwy at 70 I get between 24.6 and have seen 27.6 MPG now. I have put bigger off road tirres on but still see 22 to 24 MPG.

But no lack of power it runs fast now

One more thing copy link (TSB) http://www.justanswer.com/ford/17a7n-2005-ford-expedition-idles-real-high.html

 

[Fanatic1074]

Well I guess I'm buying a throttle body. I have already had all the modules update to latest software.

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[Big White]

The machanic replaced it with a stock throttle body. I wanted to use a higher performance brand but due to the fact that after he fixed the MAF wire it ran so bad and I lived very far from him I had not choice but stock. One thing I do notice with the new throttle body is that my RPM idle is 1500 where as before it was 1000 to 1200. With stock tires on fwy at 70 I get between 24.6 and have seen 27.6 MPG now. I have put bigger off road tirres on but still see 22 to 24 MPG.

But no lack of power it runs fast now

One more thing copy link (TSB) 2005 ford expedition: that idles real high when sitting..hot day - JustAnswer

If you are getting 24 mpg in an XP, I want to see a pic of the nuclear power plant you got in that thing!

 

[Fanatic1074]

Hey jb14 were u seeing ant difference in power/MPG before u fixed it when it was Cooler outside?

Mine runs pretty good when the weather is cooler.

Also I was actually seeing about 21 MPG or so on mine before my power issue with the mods I have done.

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[Fanatic1074]

Okay replace the throttle body and went ahead and added a little body spacer. Still having the same issues. However now I'm getting a check engine light. Gross emissions leak. I was curious if anyone know if this would cause the power issues or is it just another problem I have to deal with. I know what grocery missions leaks means but I can't see it creating this big of a problem on the power side. Thank you in advance!

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[joezek]

The sudden emission leak after the throttle body was replaced would lead me to think the gasket isn't sealing, or not seated properly.

I had a problem just like your describing but only it was in my Explorer. It would just die when I needed it to go- at the worst times possible. It almost caused me to be in 3 seperate head on collisions because I was caught crossing a major intersection each time with on coming traffic/tractor trailers. -every time it was the same exact scenario. It would always be after driving one continous 40 mph speed for more than 4-5 min, followed by a stop for about 20-30 seconds. Then what would happen is I would step on the gas, it would start to go normal, then after about 1 second it completely died, and as soon as I let off the gas it stumbles back to life but barely any power for a few seconds. Also, it was always while making a left turn FWIW. ---So I came to the conclusion that while cruising at low speed the fuel was vapor locking ( or close to that point of boiling) somewhere in the fuel line under the hood. I looked over the fuel lines closely, and realized that the two braided fuel supply/return lines were just about touching the exhaust manifold on the driver's side. I repositioned them, and suddenly this 1 1/2 year old problem disapeared.

Maybe you have a similar problem, fuel related. What is it doing exactly? Does it stall, or just get a little weaker, or drop to idle power only, or sound like it's just dropping one cylinder?