capncaveman20

I know this subject has been discussed numerous times. The issue in my 3 day search is that no thread follows up with a fix to the issue.

I have a 2006 5.4 3v with 149k. When the truck is in overdrive, i coast downhill into the next incline and when i slowly press the accelerator i feel and hear a pretty distinct thud. This only happens with slight accelaration and in over drive, it may occur 1, 2 or 3 times consecutively but once the truck shifts to a lower gear it isn't present. I have never experience this with overdrive turned off. Has anyone experience this issue and have a solution to the problem? Any and all suggestions on where to start would help me out!

I think I will start with greasing the slip yoke. What else should I be aware of?

Aeromech

I have your answer but you aren't going to want to hear it. Why, because it's just too easy to fix and you think that whatever it is... it must be hard or expensive.


Preface: I own a 2006 Lariat 5.4 3V with 170K miles and I HAD the same problem and was also convinced I had a much more difficult problem. Then I read this thread: https://www.f150forum.com/f4/bog-dow...solved-166431/


Now that I've replaced my bad air filter seal my stutter (bog down) and moan is gone. Take a look at your seal. I'll bet it's bad. Humor me.


EDIT: Skip to the last couple pages of that thread for pics I posted

capncaveman20

Thanks! I will give this a look tomorrow and will humor you. I really hope it is that simple, i was expecting the worst.

powerranger262

Something else simple to do, and should be part of basic maintenance, is cleaning your MAF, throttle body, and replacing the fuel filter.
What is your mileage, and were the plugs or COPs ever done?

tareed94

Lemme guess, you're between 40 and 45 mph when it does it huh? This is a common symptom when the plugs get old. You can develop an intermittent misfire that will thud like that under light load when OD is on. If you turn off OD it will stop if this is the problem I think it is.

My information comes from personal experience with my plugs doing this, what I found when I thought it was the transmission, and what the transmission shop told me when I took it in for a transmission rebuild quote.

capncaveman20

That is exactly what I am experiencing. I am a relatively new owner of this truck, have had it for about 8k at this point. So I am unsure of the maintenance history. My plan is to take care of all known issues with this truck before the become present. I have already gotten plugs for the truck and plan to dive into that soon as well. I did check Aero's suggestion and the foam sealer on the air filter is none existent, so why not start with that! I appreciate all of the responses, this place is awesome!

tareed94

If/when you do decide to tackle the plugs, save yourself some headache and get the Lisle spark plug removal tool on standby. I'm sure you've seen some of the nightmare stories that others have posted. It's not horrible to do yourself if you have the tool. I actually used an impact on mine the first time I replaced them (they had roughly 130K on them because the previous owner didn't replace all 8, they did 7/8...). My procedure was loosen 1/4 turn, spray down with liquid wrench, tighten back, loosen off 1/4 turn again, spray and let soak overnight. The next day we put an air impact on them and hammered down until they came out. If you do this approach beware, when the plug starts spinning don't stop. If you stop and start again the plug will break. Oh and regardless of your procedure, run fuel system cleaner before removing them. It'll help break the carbon off of them.

Aeromech

I did check Aero's suggestion and the foam sealer on the air filter is none existent

The thud does feel very much like a misfire. My plugs have only 30K miles on them and I wasn't getting a misfire code to latch. Then I read about the air filter seal. The first repair I did, I used a thin soft foam with an adhesive backing. This helped but I still had somewhat of the same problem. Then I replaced that foam with a rubber bead seal that also has an adhesive backing. So far so good. I haven't had a cough since.


The cough makes you think it's an overdrive problem because when you click out of OD it stops. I think it's because the RPM's increase. For me, the cough would seem to happen more when it's hot out. Hot equals thinner air your engine is breathing. The leak in the air filter cover I think causes the fuel injection to run too lean because air is bypassing the air flow meter. I would also get a moaning sound during this low rpm (1300-1400) acceleration and now that's gone too.

capncaveman20

I plan to add new air filter seal this week. It is my first plan of action because it is so simple and do nothing but improve the performance of the truck. I hope this is it and fixes the problem but I am skeptical that this is it (I think we all expect the worst when you feel that "slip"). I do not know the history of maintenance on this vehicle at this time but plan to ask the dealership if they have record of the trucks past, when I take it in for maintenance next week. Hopefully they can let me know when and if the plugs have been replaced, if not I am going to go ahead and take that task on too. Again, it can't hurt to have new plugs either. Again, thank you Tareed94 for the info about replacement. I have been reading until my eyes bleed about replacing the plugs and feel pretty comfortable. KEY: DON'T RUSH THE PROCESS!

tareed94

Glad I could help! If you don't let the plugs go way past when they're supposed to be replaced it's simple to get them out, and less likely to break off.