Need some help diagnosing an issue -

I have a '03 F150 4.2 v6 that has all of the sudden developed a nasty vibration in the accelerator and a dash rattling noise when accelerating. At first I figured it might be broken a motor mount(s) but I don't see the typical engine twist / lifting usually associated with broken mounts. Basically the truck was fine one moment and then after starting the vehicle and leaving a restaurant it started the vibration and noise. Which again kind of leads to my thoughts about a mount being broken.

I know the mounts have a U like setup which would minimize any movement but just didn't see any at idle and shifting into drive/reverse.

Unfortunately wife was driving it at the time so I have no real insight as to what occurred before or after this started to happening.

Thanks folks

 

With the hood open and motor running, stand at the side of the truck and have someone put it in gear. with the brakes applied give it just a little bit of gas and see if you have any excessive engine "lift", repeat process in reverse. That should tell you if the mounts are good.

Also take a good look at the fan and water pump for wobble. Then check the drive shaft at the U-joints and where the slip yoke goes into the back of the transmission.

From what you described, that is where I would start looking.

Good luck and post back what you find.

 

You sure it's not just misfiring?

 

^^^That is more likely. If it is there should be a CEL flashing when it's "vibrating".

 

Ok.. well figured out the issue after doing some more digging around, and feel kind of stupid for not seeing the tree in the forest earlier

Found that a factory lift point that I believe was originally attached to the drivers side manifold had worked its self loose over the years and managed wedge its self between the engine and firewall. Not quite sure how or why it just plain didn't fall out but never the less I removed it and appears all good now.

If I remember correctly these mounts were just attached to the studs on the exhaust manifolds and I don't believe that there were actually used to hold anything "together". Just curious if should go back and look for anything else that might be loose.

 

There should have been 2 lifts, front on one side and rear on the other. What happens is the double end stus breaks odd at the hex part. You should be good to go!

Take a look and get the other one out of there also. Mine came off on the freeway and bounced out and hit the side of my truck, nice scratch/dent. I get PO'd every tine I look at it!

Thanks for posting your "fix".