I have a 2004 F-150 with about 98xxx on it. The problem I will be describing has been going on for about 2 years now, but is becoming much more constant.

My truck has no modifications to it. At about 75xxx I had the Cam Phasers replaced, timing chaing tensioners, etc. I also had the spark plugs replaced at the same time. Also have regular maintenance done.

When at a stop sign and slowly accelerating from it, I will get a loud moan/bogging sound. Usually only going about 5-10 miles per hour at this time (1500-2000 rpm). If I let off the accelerator and press it again it usually goes away or if I just press on it harder, it will sometimes fight through it and then just take off quickly.

This problem can also happen at highway speeds. When holding steady pressure on the accelerator, this sound will also happen when I reach the bottom of the hill.

These problems don't happen all the time. But they are becoming more frequent. Shops cannot figure it out or can't replicate the problem when they have it. It also seems to get much worse during warmer temperatures.

Please help!!!

 

I'm assuming the fuel filter has been changed?

 

Yes, fuel filter has been replaced.

I also have never had a code thrown for this truck. No CEL.

Also, if I pound the accelerator and drive aggressive, the problem rarely happens.

 

I'm wondering if it may have something to do with the torque converter.

 

Sorry, forgot to mention the torque converter was replaced too. A family friend is the service manager at a local dealership and replaced a bunch of stuff for me before my warranty was up. They couldn't figure out this problem so they just started throwing new parts into the truck to see if it was the problem. New torque converter and new gear pack in the rear end were installed.

 

It almost seems like the transmission isn't shifting correctly when this problem occurs. But it seems to happen at different gears. And two different shops last summer said my transmission seems fine when the drive it. So I'm still torn, transmission issue or something else engine related.

 

See if anything might be loose and blocking the air intake.

 

... I am still trying to understand... what is the problem again?

 

When accelerating from a stop sign, I will get a loud groan/moaning sound, as if the engine were bogging. It doesn't happen all the time. It is more frequent in the warmer months and after the truck has warmed up.

While this loud bogging sound happens, the truck fights to get moving.

This same sound will also occur when traveling at highway speeds and hitting the bottom of an incline.

In both instances, if I punch the accelerator instead of slightly increasing the pressure, it doesn't happen as frequently.

 

Has the throttle body and MAF sensor been cleaned/checked?

 

Have it schedule to get that done tomorrow. Along with a reflash of the PCM.

 

TruffleShuffle: My 04 followed the same patterns you described for almost 2 years/20,000 miles. One morning as I passed a semi on the highway using gradual acceleration and it did it for the last time. I had had enough. I hammered the accelerator pedal through the floor, and miraculously the dash lights up like a Christmas Tree; throwing warnings, wrenches, codes etc. It went into limp mode for a quarter of a mile, and then settled back to normal. Pulled the codes when I got home and they indicated misfire on cylinder 8. Replaced that COP (coil) alone and never had an issue again (1 year, 15K later).

Hope this helps!

 

I to have this exact problem. I have done all the maintence as well. My question is if I dont throw a code is there any way to know which COP or if it is truly the cause of my bogging issues? Any testing? etc.

 

I just fixed this same problem on my 2004 FX4 on Labor day. What is probably happening is the air-filter tray is not sealing to the throttle body right and the engine is sucking hot air off the top of the engine and messing with its performance. This is why this happens when the engine is hot and it gets even worse with summer temps. All I had to do was strip the foam seal off of the air-filter tray and put something like weather stripping or two-sided foam tape back on. In my case, the tray was bulging out at the bottom and I couldn't get it to stick to the TB so I finally had to drill holes into the tray and into the TB on the bottom side of the filter, and stick some screws through the holes to make the tray flush with the TB. Now my truck hasn't groaned one time in over a week. I did however have to reset the fuel trim by removing the neg battery cable and turning the lights on. If you've driven the truck like this a while, the trim numbers may be all jacked up from hot air hitting the MAF.