[peegh]

Hey i was just wanting to get some idea's where to look. I have a 82 gmc sierra 2wd with 6.2. The motor runs good but has a shake when idling that my brothers 86 and my fathers 83 doesn't have. I have no power issues, no missing, no stumbling, the injection pump is right on the mark with the timing cover. The motor is not losing coolant and uses very little oil (mostly leaks at the fill tube seal). what should I be looking at? Thanks in advance for any assistance. Oh and I have two new motor mounts and transmission mount on it.

 

[High Sierra 2500]

Sounds like it has a miss at idle... Maybe a bad injector or it is losing compression on that cylinder for some reason. Does it change as the engine warms up?

 

[farmer0_1]

dads 85 suburban shook at idle and it ended up being the inj pump. put a rebuilt on it and off we go.

 

[4DR4X4]

bad injector or pop pressure off will do that.

 

[peegh]

Thanks I was thinking the injection pump. the motor doesn't seem to miss at idle. if you crack the lines it changes the sound at each cylinder so I don't believe its missing at a cylinder. You even notice it when you speed it up some. I wondered if one of the injectors wasn't putting the same amount of fuel as the others causing it to maybe be out of balance.

 

[farmer0_1]

dads suburban gave you a good strong vibration up the steering wheel until it got going down the road.

 

[Fred482`]

My pickup shakes at idle because of low cylinder pressure (compression) from 240,000 miles of normal wear and tear. It still produces good power and mileage. Bring it up off idle, under load and the shake lessens. I'll fix it when it breaks!

 

[jdemaris]

I wondered if one of the injectors wasn't putting the same amount of fuel as the others causing it to maybe be out of balance.

I don't think that's possible. The amount of fuel delivered at each injection stroke is determined deep inside the pump by the stroke of two plunger-pistons - and is then sent through a distributor where it is redirected to whatever cylinder needs it next. Not very different in operation than a gas engine distributor in the cap and rotor. The fuel injector determines the pressure, not the volume. Now, a scratch or wear pattern in just one section of the head & rotor assembly can affect just one cylinder. If so, there is no way to repair it other than complete replacement of the head & rotor assembly.
There are many other things that can cause an low speed power-inbalance. The newer, electronically controlled GM diesels monitor engine power on each individual cylinder and can even an engine out by controlling injection on an indivual cylinder.