hey guys
when i go up hills my check engine light goes on and the truck seems to run a bit weaker. then on flat surface it goes off and stays off until another hill. any clues on what is could be?

 

Easy way to find out is to pull the stored trouble code. Depending on what truck you have you may be able to do that without a code reader.

 

i got the 1993 f 250 xl

 

Then on the top line of this forum page you will see Tech Info right next to "Read First" in red, click on that and then on OBD1 self test for instructions on getting the trouble codes using the blinks of the check engine light.
This way the computer can sometimes tell you what is wrong and saves throwing parts at it.

 

I get the same symptoms but no check engine light. It gets week under load and get alot of clattering. I have been through the timing and EGR ect... and the truck runs very smooth

 

my 7.3 excursion does it with a load or slamming on the throttle. If you find out anything please let me know.

 

Your timing isn't set right or you have an excessive amount of carbon buildup on the piston crowns. What is your timing set at right now?

 

That makes sense. Maybe I should check my timing as well..