Fuel System Problem - pump or regulator?

I have a strange problem. My car runs fine for a week, 5 days, 2 days etc. Then, you can punch it and it will stumble. It might stumble for 2 - 3 seconds like it wants to run out of gas then it will pick up and run fine. It might do this twice in 5 minutes then run fine for another week, 5 days, 2 days etc. It is kind of embarrasing. I don't know if my fuel pump is starting to fail or my fuel pressure regulator is going bad or what. Please help me. :banghead: It is a 1999 Malibu 3.1 with about 178K miles. I have never replaced the fuel pump, althopugh I had the sending unit replaced about 50K miles ago.

Replaced the pressure regulator and it still showed symptoms.

make shure that filters are good and replace the cheaper one either the pump or regulator.. if problem still occurs then it has to be the other one.



i have an 81 malibu and it has a similar problem.
there is a flat spot on it. so i am going to replace the tank, lines,and carb. i am hopping that their is just some rust in the tank and it keeps clogging the carb. this will be the 3rd carb on it.

Thanks!

I have never replaced the fuel pump, althopugh I had the sending unit replaced about 50K miles ago.

Typically, the replacement sending unit (at least through the dealership) includes the float, the level sensor, the baffled reservoir, and the pump (the entire in-tank unit). If that's what was done, and the replacement part was about $350, you probably already have a new pump.

Before throwing any parts at it, test fuel pressure.