I'm new to the forum so please excuse me if this has been posted already.

I have a 2007 ford f150 5.4l crew cab 3.55 rear axle 85,000 miles 4x4.

I just bought this truck new from a car lot with a 36m/38,500 mile warranty. The dealership cant seem to find the problem as the truck hasn't thrown a CEL. I tow a 1200lb UTV on a 900lb trailer so I'm now where near putting this truck to the extreme. It doesn't happen at every light it normally only happens once or twice when towing my toy but when I pull up to a stop light the truck will idle down around 300rpms and the engine and truck will start to shake like its going to stall. I have to hold the brake and give it gas until the light changes. I can go down to the next light and it wont give me any troubles. This a random rough idle. over a 100 mile trip it might do it 3 times.

Look for some kind of direction to point the mechanic in or maybe something simple I can do my self.

thanks,

 

Having 85k miles, there is a good chance it may still have original plugs and coils in it. When it comes to rough idling or misfiring, I think most people on this site will say to change your plugs and boots at least. Unless you know for sure they have been changed recently.
Good luck!

 

I know for sure the COP, Plugs, & wires are all new. I no its also got a new air filter in it as well. I haven't pulled the air box off to get to the throttle body to see if it needs cleaning. I feel like if the throttle body needed cleaning then it would act up a lot more then it does...
Like I said it doesn't do it all the time just every once in a while and I have narrowed it down to happening only when towing, but even at that its not every light it does it at.

 

TB needs to be clean and check the "Fuel Pump Driver Module" under the spare tire. If it doesn't have spacers(air gap between it and the frame) replace it!
1. 2.

 

Great videos. I will defiantly take a look at both...

 

While doing both of those that were recommended, also clean the maf (use only mass air flow sensor cleaner) and replace the fuel filter as well if that hasn't been changed within the last 15k.

When cleaning the TB, be carful and don't force it open and closed. Don't be scared though, I clean my TB every year and haven't had a problem.

Even though there is no CEL, are there any pending codes? If you have a scan tool, it'll show you pending codes that have not yet produced a CEL.

 

Yes, clean the MAF

 

Try a 5w30 oil.

I bet your chain tensioners have a bit of a leak. When you're towing your oil temperatures are higher than normal and the oil is thinner...making your cam phasers throw your valve timing off and make it shake. I had the same shake/low idle after putting in a very light 0w20 oil (TGMO). Happened after a highway run while trying to back up. I drained the oil right after and installed castrol 5w30. Never happened again. I run castrol 0w40 right now and the engine runs super smooth in all conditions.