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Q: I am having a problem with degraded acceleration/mileage.

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My truck hesitates, coughs, and slow to respond to gas pedal inputs. It will accelerate to 55 +/- but very slowly. In park the engine will not go above 4000 rpm and starts to cycle up and down about 800 rpm whem it reaches 4000. It gets a check engine light, (OBD-1 system) and reading the codes points to "higher than anticipated fuel pressures. It also will just quit accelerating while at highway speed and releasing and then pressing down on the gas pedal will usually recover it. I have changed the fuel filter (3times), the fuel pressure regulator, the fuel pump and the fuel injectors. I also recently swapped out the engine brain (PCM) and no improvement. This problem has persisted and gradually gotten worse over the last two years. The truck is now beginning to stall/not start right after it has been driven. What sensor(s)/parts can be causing the problem?

My car has 95560 miles.
My car has an automatic transmission.

A: I would recommend checking/testing the O2 s...

I would recommend checking/testing the O2 sensor and the MAF (Mass Air Flow) sensor. When either of these two sensors are not working properly, as you may know, they will send inaccurate signals to the ECM which will then, in turn, be making incorrect changes to the fuel system. It looks like you already had some work done on the car, so it may be smart to get an official diagnosis on the issue before moving forward with another replacement. If you want to have this checked, a certified mechanic, such as one from YourMechanic can come to your home or office to diagnose your acceleration issue and let you know what should be done.

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