i have a 1989 gmc r3500 with a 454 that giving me a code DTC - 44. so far ive replaced the fuel pump and the o2 sensor and cleaned the egr valve.i was wondering if you guys think it could be the fuel pressure regulator or a vac leak?i was also think about blocking off the egr vac line and seeing what it does.

Unfortunately lean codes can be tons of things. Fuel pressure goes down when the pump goes or anything wrong with the connection or ground. Any air leak. You can use carb cleaner to check for leaks

i check for air leaks and i found none.i was thinking could the coolant temperature sensor cause that code.so far im leaning towards the fuel pressure regulator.

also what about the map sensor?

Does this have the 4bbl carb or the efi(electronic fuel injection)? That year could have either one.

its got the fuel injection.most sites ask for the vin letter and mine is a n.

the ect does cause fueling issues you can test it;


o2 normally has different codes. you can check pressure but you have to get something to tee it off. if the pressure falls off quickly the regulator is bad. if its not over 10 something with the pump or filter or wires

i think i might have notice something today.the lean code doesnt seen to pop up until the truck get warmed up.could that be the ect or is it more likely something that fails when it gets hot.

may mean its good the truck runs in open loop cold then tries closed after it warms up, which is stricter tolerances,

your probly right.i just changed it and it didnt fix my problem.i guess its back to the guessing board.