engine idle

[Cummins Cowboy]

About a month ago i turned up the fuel on the pump. I turned the fuel screw approx 1. 5 turns. This helped a little although not as much as i thought it would. It does have a little more power. Now i have noticed that once the truck has been sitting running(idling) for more than a minute after the engine is fully warmed up the engine idle somewhat lopes the rpms vary about back and forth about 50rpm(between 850-900)any ideas??? is this normal??? could there be anything wrong with the pump???

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93 D250 5sp 3. 54 gears sans muffler, ISSPRO tach, K&N filter, needs to be bombed BAD
I would rather be cummin than stroken

 

[DJP]

After I turned my fuel screw in one full turn, I noticed a big increase in power and black smoke. I also noticed the idle speed seemed a little higher too. Yesterday, I turned down the (low) idle screw about one full turn, and turned out the (high) idle or governer screw one full turn. When I drove the truck after the adjustments, it seemed to have lost power, had increased turbo lag, and a signifant reduction in black smoke. The idle seemed to be set a little too low, and the idle rpm seemed to fluctuate slightly. Today, I turned the (low) idle screw back in one full turn and got the power and black smoke back. Since I don't have a tachometer, the idle speed was set by ear. Right now, idle rpm seems just slightly high but the performance gain is well worth it. Try turning up your (low) idle speed a little, and see what kind of performance gain you get.

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89 D-250 LE 5 speed 3. 55 Limited slip, Banks Intercooler, 'Ol Blue Specials, K&N, Full Boar Muffler, 3" exhaust, Diesel Dynamics Stage 1 kit, Boost/Pyro. & 16cm2 215K miles.