Friend of mine has a 98 1500 with a 5.9 gas engine. Problem is lose of power around 3500 rpm like it's got an obstruction in the tailpipe/no air/not enough fuel, runs and pulls smoothly up till just over 2300 rpm or so. After a few tanks of gas the problem went away, then a few tanks of gas later came back. If we stay in the peddle trying to pull a grade the check engine light will flash till we get off the gas. If we stay on the gas long during this condition the check engine light will stay on with a cylinder miss fireing code, like cyl.#5 missfireing or such, a few starts later and the light goes back out. Intake has been checked for blockages, rotor/cap/wires/plugs recently changed, about 95 thousand miles on it. Books say there is no servicable fuel filter. Otherwise no check engine light and truck runs smoothly with regular gas milage going down a level highway. Get on an overpass and let it kick down (automatic) and it falls on it's face.
Please help, thanks.

Jman

 

Hit the bottom of the Cat with your fist , if it rattles or anything , it's toast, happened to my dad's 150 w/318 , cat broke apart and blocked the tail pipe , had the same symptoms.

 

Make REAL sure it has cooled off first.
Cat Converters can reach temps in the thousands.
3rd degree burns will mean a trip to the ER.