Rattle sound from under carriage
 

I am sure there is a couple of threads on this already, but have had a hard time finding my exact issue.

Just to give a history. I added a cold air intake and an Edge Evo programmer to my 2004 F150 Supercrew 5.4L 2wd truck and it did nothing but bad to my truck. Once I installed intake, my throttle response was horrible, so I removed it and went back to factory intake. The EVO burned out my VST Solenoid, so I had to get a new one and replace it. Truck was shuddering on stress and $600 tune up fixed that. I have removed everything except a flowmaster exhaust. All seems good now, but I am getting rattle from under the truck now when I am stopped at a stop light. If I put the truck in neutral, the rattle goes away. Also, when I am stopped and turning my steering wheel while in drive, the truck sometimes acts like it is about to turn off. The rattle is annoying and hope it is not going to cause more damage.

Any thoughts of what it can be? I have read the usual, heat shield or cat possibilities, but doesn't seem to be anything loose underneath. When the truck rattles, if I rest my foot on the gas and increase the idle a little the rattle goes away and sounds smooth as butter. Is my idle running to low and need it reset? If so, does that have to be done at the factory? I have seen some videos and threads on instructions on how to reset my PCM settings. Will that reset my idle?

Any help would be greatly appreciated?

I am about to add another flowmaster to have true dual, but want to fix this rattle first.

I had the same issue on my 01 and it was exhaust issue wise cant remember if it was heat shield or the cat. Good luck

Thanks

This, check the heat shield it may be loose, if you have an aftermarket muffler still the heat shield may be rattling around I had a similar problem with my factory exhaust on my old 02 explorer with the 4.6 the heat shield bolts wee all rotted.

I checked the shield, but I will check it again.

Has anyone tried resetting their PCM? Is resetting your PCM the same as resetting your idle?

Like stated above sounds like heat shield. I had the exact same issue on my last truck, my heat shield over my cat was loose and somehow a rock got thrown in between the cat and the heat shield, and the rattle drove me nuts.

If it is a heat shield take one of those metal pipe clamps with the hex head screws and tighten the heatshield up around the pipe The same thing happened to me

I will try that

I finally got it to make the sound while I could be under it and the vibration sound is coming from the flowmaster I have on it. When I press something up against it, it stops rattling. Seems like either the idle is so rough it is causing the muffler to rattle or there is something lose inside the muffler. Doesn't sound like there is something loose inside the muffler. I think my idle is too rough.

I just unplugged my battery and am going to go through the relearning process to see if it helps to smooth out my idling and/or fix anything else that could be causing the vibration. Hope this works.

Can you pop you muffler off and give it a shake? Or is it welded?