Hope some of you old timers can help me out. Truck is a 93 i/c a518 161k runs great but it's very slow and gets 11mpg loaded to 10k gross. Fuel screw turned in about 3 turns pin has been turned and timing bumped about 1/16
It just feels irrepsonsive at the pedal, you have to **** near mash it to the floor to get going, throttle linkage is tight and moves to the stop. It does roll smoke at full mash down and takes a few seconds to clear up. The truck in my sig will run circles round this one! Thanks in advance

 

Fuel filter?

Bad lift pump?

Dirty / tired injectors?

Throttle shaft index?

Bad torque converter?

Slipping transmission?

Parking brake on?

 

What NotEnuf said or leaky intercooler or pipe or boot?

 

My guess is (esp if it has been lightly loaded or worked) is the fuel system needs gone through- new pump springs and injector pop pressures reset. everything cleaned and reset. I have never gotten worse than 13-14mpg with a CTD towing, and that was hay at a 24K gross.

But, before you go that far, check the following-
Lift pump output pressure. If it is low, the pump wont have the fuel volume to properly compound the pressure to send fuel to the injectors.

Timing. Find true TDC (use the timing pin as a guide only for adjusting valves, never for pump timing til you find out it is or isnt accurate) and set it where you want.

Valve adjustment. THis can make it sluggish and suck the fuel, too.

Get the injectors checked. Most fuel system shops will put them on the tester for free, and my local shop charges $10 apiece or so to clean and reset the pressures.

 

Does the idle screw seem to be in a long ways? A mis-clocked throttle lever will cause those symptoms, and if you run the idle screw in far enough to get it to idle it will run and drive - it will just be really laggy and weak.

 

Filter is new, lift pump isn't too old but I need to check pressure (not sure where to hook up for that one) adjusting valves today, and the injectors need checked as soon as I find a place in the Phx area

 

Idle screw only showing 1/8" of threads where it hits the throttle plate

 

Well, that ain't it.