Skip the auto shop - Our mechanics make house calls

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

asked by on

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Sometimes the truck will start and run just fine, and other times it will barely want to start and I need to press the gas pedal

Hello. This can be caused by a few different things. If the vehicle will run by pressing lightly on the gas pedal then it may be a bad idle control valve. If it sticks, it will allow too much air...

Q: Clicking under car when accelerating

The sound you're describing sounds a lot like an issue with your wheel bearings. This type of damage is very common on Outbacks, especially if you enjoy light off-road driving in the mountains or hills. You indicated that you...

Q: engine is missing an surging an idle is rough - 1994 Mazda B4000

Hello. This sounds like you have a lean running engine. This can be from carbon build up on the valves and dirty or clogged injectors. Have the combustion chamber and injectors cleaned. Then see if the engine runs better. If...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...