1988 F250 302 4x4 5 speed

Here are my issues:

The truck engine would vibrate/flutter when driving and I thought it was the injectors and the truck needed a tune up. So I replaced all the plugs, wires, cap and rotor and timed to specs.

The engine idles perfect and smooth when I accelerate. Also I just replaced the Air Pump Check Valve that popped off the line making lots of noise thinking that might be one of the issues.

Took it for a spin and still did the same thing no matter if it’s in 4x4 High, low or 2 wheel drive.

I found out if I put the gears in neutral while driving and rev the engine it does NOT vibrate and it’s smooth.

It’s when I’m in gear while driving when the engine vibrates.

I’m thinking it might be a motor mount. IF so, How can I tell if one of the mounts are broken.


Does anyone have any ideas what is causing the vibration /flutter while in gear?

Thank you,
Runner

 

I check the motor mounts and they are intact and good.

Another thing to mention. Would anyone know what this wire plug is for where it plugs into?

From what I can remember, this was always unplugged. Maybe I"m missing something here.

Plug 1_zps7kmvidql.jpg Photo by jagrunner2602 | Photobucket

Plug 2_zpskadwg0on.jpg Photo by jagrunner2602 | Photobucket

Also still need some help with the vibrations.

 

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