Q888,

I had a slight (felt like misfire) shuddering, shaking at around 1500 rpm ('95 with 5.2 and no cat) just like you are describing. This is after I changed a non-working injector. I put a can of seafoam in my FULL tank of gas and now I am just below 1/2 tank and the truck runs GREAT. Have you tried this?

Laters
Joe

 

Did you figure out your problem?,,,My 98 1500 is doing same thing,

 

Fixed the shutter (read: vibration shaking).

Harmonic Balancer (vibration dampener) $89.95 OEM Part
Front Crankshaft Seal (while I was there) $12.89 OEM Part

Took me about 2 hours and less than a six pack.

No more shutter, shake, vibration, or misfire feeling.

What a great feeling. I was really starting to get annoyed with this and imagining the worst. Trans going out, torque converter problems, cracked head, and you name it. Glad it was something simple.

I diagnosed this by removing the serp belt which disabled the accessories then started the engine for a minute. Engine still exhibited shutter so I shut it off and got under the front end to inspect the main drive pully assembly and harmonic balancer. I found with a strong enough grip on the drive pully I could get the balancer to spin without turning the engine.

 

Sorry to revive an old thread but to be clear...when you changed your harmonic balancer it cured the rough idle?!