M1009 Low Idle Shake

[tgtaylor64]

Need some direction on solving this problem. Stock 1984 M1009 from GL. Runs great except for the shake/shimmy at low idle. Not too noticeable at cold start-up fast idle. When it switches to low idle the motor shakes the front end and sounds like it is skipping. Lots of smoke. Motor mounts look OK. Replaced all the injectors last week with no change in behavior! Not noticeable at speed, very smooth running. I have checked the fuel lines and tightened all of the fuel connections. Do you suspect an air leak somewhere? Where are the usual suspects? Fuel filter is stock. Could it be starving at low idle?

 

[85CUCVtom]

You said it has the stock filter setup, I would start there. Those had a tendency to leak.

 

[gungearz]

Do you use diesel treatment....? could possibly have a lot of condensation in the tank...

 

[nyoffroad]

It's not starving for fuel cause it runs good at a higher rpm.
Possible air leak, but the rough idle would go away at higher rpm and then return SLOWLY at idle.
What is the idle RPM? Could it be as simple as turning the idle speed up a quarter or half turn?
Worst case I can think of would be low compression on one cyl. That could be the cause of the skip and smoke.

 

[tgtaylor64]

I use diesel treatment with every fill up. I don't know the actual RPM, but the problem will decrease if I turn up the idle.

 

[2002ford]

I believe the correct warm idle is 650.

 

[Recovry4x4]

I run all my 6.2s a little higher on idle. Low idle will rattle the filaments out of the headlights.