I have a new to me 1985 3/4 ton Chevy Suburban 6.2L diesel 4x4 with a three-speed tranny and NP 208 transfer case. 119,000 miles.

The truck runs great at first(fires up easily) but as the day wears on, the idle gets rough, so rough I get a bit of shaking in the truck. There is no smoke that I can see either at idle or at speed/acceleration. I also seem to be losing power as the day goes on.

I have changed the fuel filter. Is it an injector?? I just need some idea on where to start. Thanks in advance!

I have a similar problem in that mine runs great and lots of power, but it shakes the snot out of my truck. Any idea on what it might be?

I WOULD HAVE TO GESS YOU HAVE BAD NOZZEL GASKETS. AS YOUR ENGINE WARMS UP AND YOUR HEADS EXPAND YOUR GASKETS ARE LETTING EXESS AIR IN. JUST A GESS. CHECK THE TORK ON THE INJECTORS. ALSO IF YOU HAVE ACCESS TO A RAYTEC THERMO GUN YOU CAN SEE WHAT CYL. IS NOT FIRING. IT'LL BE COOLER THAN THE OTHERS

Ringer: Run the engine at the maximum roughness and loosen each injector nut (to leak fuel) one at a time to see what happens. When the bad injector is lossened then the roughness want change much, but when a good one is loosened then you will notice the difference. I would remove the bad injectors and have them tested and rebuilt. If the rebuilt injectors don't cure the problem then you could have a bad piston in the injection pump which would mean you would need a rebuilt injection pump. In rare cases a leaking lifter can cause problems when the engine gets hot. Let me know what you find out in your trouble shooting.