Truck is chu-a-luggin

[frank_m64]

So I have an 84 pickup, i switched out the motor and tranny a few months back and everything was good up until this last weekend.
I drove it down to Baja and back, it made the trip fine. until I had to wait in line at the border. The idle became a little "weak" I guess, i never died or stalled out on me but i could feel the difference.

Since then it idle has been really rough, the best that I can describe it is it chugs like a train, or thats what it sounds/feels like. I checked the spark plugs, the rear two were slightly soiled but dry.

Seeing as I had changed them when I swapped the motor I figured maybe they "went bad" I bought two new ones, changed the cables and for good measure bought a new rotor and distributor cap. no change.
I can loosen the cables and i see the spark from the cap to the cable.
Also the exhaust smells of unburned gas.
So im at a loss as to what is happening.

any help would be great

thanks

[Jayota]

have you checked your timing?
any intake leaks you are aware of??

[Tech1984]

Sure sounds like a valve problem. Do a compression check.