My 2000 k1500 would surge/jerk under light load going up small hills in 4th gear and lose speed. I called my trans guy he suggested a lean condition. So I replaced the plugs and wires and the problem went away. Couple months later it's back, same problem. The truck has 140k miles on it and haven't replaced any of the sensors but don't have any check engine lights on either. Thanks for any help
The first thing to do is to scan the system for any trouble codes even though you said there aren't any. You may have codes stored in memory even though the light is not on. An intermittent condition will store a code in memory and not leave the light on.
The scanner can give a lot of information on the running condition of the engine and transmission while you are driving under many different driving situations. If one of the electrical components of the transmission or engine is causing this problem then you will probably see it on the scanner while you are driving.
When was the last time you had your fuel filter changed? A clogged fuel filter can sometimes give this condition.
A blockage in the exhaust system like a catalytic converter, pipe or muffler can contribute to this condition.
Checking the performance of the fuel system and checking the back pressure of the exhaust system can help narrow down the possibilities.
You still can't forget that the ignition system can still be at fault. The ignition coil or one of the coils (If you have the coil near plug system) can be at fault and should also be checked out. You could even have a bad plug. It's been known to happen.
Remember scan the system first, check the rest of the ignition system, check the fuel system then check the exhaust system for back pressure.
Let us know how you make out.