shaking when holding speed

:redface: my 92 s10 shakes or jerks when i try to hold a constant speed .when i accelerate it doesnt do it and at abou 50mph i cant realy notice it. i tried to change plugs and wires,it dident help. 2.8 LTR moter 2wheel dr. 150,000 miles. ps. not trans problem.........................any 1 help please

If the vibration is speed related and not RPM related, you will not fix it by working on the engine.
Check tires, front-end alignment and driveshaft U-joints. A bad u-joint will sometimes only shake at certain speeds and be smooth above and below that speed.

sorry thanks for response but the motor is dieing out on me and its running very rough.not u joints or drive train. i should of put that before.sorry was very sleepy.anyway not sure if egr or something electronic. i also put new fuel filter cap roter it was backfireing out carb but with prem. octane it does not do all this if i the check engine light comes on after i drive for 1 or 2 hrs.
please help ................thanks rob

My 1996 S-10 is doing the same thing.

A friend of mine said that it could possibly be the coil, you may want to check into that.

hey thanks i will try that. could be that i guess not getting hot spark.

I worked on my son's 92 chev.pickup which had a 6cyl I went through the electrical system and got most of the shaking out but going up hill it would just start shaking. Somebody had installed an aftermarket egr valve. It had a slot for a washer with a certain size hole. I talked to the previous owner who used to work for me but was a junkyard mechanic at this time. He didn't have any spacer I looked for some I had saved but they wouldn't fit. I found a washer the right size and thickness and tried about 3 or 4 hole sizes until it ran correctly.

it was the EGR solenoid thanks lot 4 the help[:licka: