Vibraton
 

I've got a 87 Sierra Classic and i have a huge vibration in the motor. It is a 350 fuel enject. It has the vibration when it is about 2-3 thousand rpms and when i accelerate. Not sure what the problem could be. If you have any info on what it would be can really help me out.

Thanks

Re: Vibraton
 

Boy: youve opened a real hornets nest here. 1. it could be anything from a fuel injecter thats dirty to a mismatched piston, also valve train problems, bad plug or wire, you have to check each out, one at a time.

Re: Vibraton
 

The engine runs fine and I just did a whole tune up on the truck and i cleaned out the throttle body. I thought the vibration was the trans mount because the rubber was totally gone on that mount.

Re: Vibraton
 

Maybe a harmonic balancer

Re: Vibraton
 

I was thinking of that or the motor mounts

Re: Vibraton
 

How long ago? When I had my S-10 I changed the plugs & wires but didn't realize till later that one plug wire didn't snap onto the plug the boot just held it in place...sometimes the simplest things are the biggest problems, plus it's a free and quick check. YMMV

Re: Vibraton
 

Has anybody had the flywheel off lately? I believe 350's and 4.3's require an internally balanced (engine) flexplate, and other blocks use an externally balanced flexplate/flywheel. However, the wrong flywheels will bolt up.

Re: Vibraton
 

I did it last year in the middle of the summer.Then this year i went and checked it all.

Re: Vibraton
 

Does it do it while your driving or while it's in park and you rev it up?

Re: Vibraton
 

yes, when i rev it up it still vibrates.

Re: Vibraton
 

since you've already done a full tune up, i'd def check the motor mounts bud

Re: Vibraton
 

Remove all of the drive belts from the engine and crank it . See if it still does it . If not , it iis in the accessories on the front of the engine . I have seen a bent fan blade cause this and this is how I found it .
Frank

Re: Vibraton
 

Thanks Frank i will check that on my next free day.

Re: Vibraton
 

Thanks for all of the input guys. I figure out is something electrical or something not going right in side the motor but prolly something elctrical. It gets better every time i replace or fix something. Thanks again.