Big Block shimmy's
 

To start I would rather read on here about others problems and the solutions, but now I have a problem. So I am asking for help....
I have a 90 1 ton 4x4, auto, ac, xcab, 454. I have owned this truck for 12 years and it ran great up to this point. It has 130K plus miles. Never been torn down. Engine started shimmying is my best description I can give. It seems as if it is not running on all cylinders??
I replaced plugs, wires, rotary button, distributor cap.( It needed it bad. ) All these changes did not change anything. It still runs the same. I can feel this while driving. I tried to gradually accelerate very slowly and it acts like it is flooding and is going to die. Push accelerator a little farther and it will continue to run, but shimmy's bad. I've sprayed around the intake and TBI and cannot find any leaks. Note: There is a constant whistling coming from the TBI unit when breather is off and truck is idling. Truck is all original and has not been altered in any way. Any help would greatly be accepted. Thanks

I wonder if an injector is stuck open, or you have a vacuum leak somewhere. Just key on with the truck running and see if an injector starts spraying. Does the exhaust show any kinds of smoke when this happens?

Is the whistle noise new, or has it always made a similar sound? My old '89 had a TBI and it always had some noise from the injectors that was louder than other cars. Maybe does it feel like a dead spot in the throttle?

Longdistance,
Look into the possibility of needing to replace the whole distributor shaft with new bearings. The bearings are just little bronze bushings. I was having serious problems with my '90 454, and even the dealers couldn't diagnose the problem. Went to a private mechanic who told me that the cylinders were firing as much as 10 degrees off! Even showed me the bad parts, and the bearings were really worn-out, so thin that they broke into pieces in my hand!
Good Luck. Steve

NullHead I will chk injectors. It is not missing it is just like it is not running on all of the cylinders.
SuburbanStevie, I will chk the distributor shaft.
Engine idles very rough, just as if all cylinders are not hitting. I am going to do a compression chk next and then chk both of your ideas.
Note: The distributor cap looked very corroded inside, so I was really hoping the new cap would fix the problem.
The rough idle is still there and when I accelerate I can still feel the roughness in the engine through the entire acceleration.
I will let you all know if I find anything.
Thanks for your input.

454 update
 

I did the compression chk today. I only did the 2 front cylinders and didn't like the results.
Left front only had 115 psi
Right side only had 100 psi
Didn't get the same results each time. Sometimes it would be even lower (80 Psi)

Put some oil in the cylinder and do it again. If your compression goes up, sorry man, but your rings are bad. Additionally, they taught me at school to remove all the spark plugs to get an even quick rotation of the crankshaft without some cylinders having compression and some not. Turn off fuel and spark, remove all spark plugs, and add some oil to the cylinder. If the compression goes up with you add oil, you've got a problem with rings on that cylinder. If it stays the same, then then rings are most likely not the problem.

They also said to only take the reading after the gauge "bumps" up three times. Take the third bump's reading as the actual one.

You will like this Nullhead. I noticed yesterday that I could hear a clicking sound while engine was running and it sounded like a spark jumping. I'm old school and resorted back to old school. So today, I got me a long piece of hose and put one end to my ear and the other I went over the engine till I found the clicking sound it was a rear plug wire that I must have not gotten on completely. Anyway you know the rest. Engine smoothed out dramatically. Engine still is not as smooth as the 5.7 in my old 93 Z71. But I've been reading a lot and other owners of the 454 say that the BB doesn't idle as smooth. I want to thank you for all your help. And I may chk the compression psi on all cylinders later as you suggested.
I also poured to containers of Lucas injector cleaner in it today. This seems to always help the TBI unit. Again thanks.