1994 Buick LeSabre Custom

When I bought the car, it was at about 86k miles. Around about 88k, it began to have a bit of lag in the acceleration. My father and I did some experimenting, which led the the assumption that the fuel pressure regulator was the reason behind this.

Being as though the car ran decent, we put the issue on hold since I did not have the money for it. But, as soon as my car hit the 90k mile mark, my car suddenly did not want to accelerate up hills and struggled to give gas. I was told to replace the fuel filter, which I did, and it resulted with no change. Then, my dad told me to replace my fuel pump. Did that, and it ran a bit better for about a day or so.

Now the car is accelerating the same way it did before I changed the fuel pump, except when I press on the throttle, inside the car or under the hood, it runs very rough. The car idles fine however.

Today, as we worked on it, we were advised to replace the throttle position sensor. Did that, only to have it continue doing the same thing. We also disconnected the battery so that the system could reset. Also, throughout this whole process, the "check engine" or "service engine soon" light has never shown up, which leads my father to believe that somebody has tinkered around with something in the vehicle prior to my purchase.

So, with a replaced fuel filter, fuel pump, and throttle position sensor, all brand new, the only thing left to replace is the fuel pressure regulator. However, another mechanic tested the regulator, only to see that it is functioning correctly, although, he said that he would not rule it out of the equation.

Can anybody help me with this issue, because I really need this car to perform fine being as though this is my only vehicle and I don't have the money to get another car or pay a mechanic to fix something that my father and I should be able to do.