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Q: Engine chugs while acceleration

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My truck sounds like it wants to die when I accelerate while in gear. It idles and revs up fine while in park. I changed feul filter and added sea foam n it improved but still had issue n is now back to way it was. Checked feul pressure n it was good.

My car has 170000 miles.
My car has an automatic transmission.

While adding sea foam and replacing the fuel filter are very good services for your truck, I wouldn’t expect them to fix your issue. Usually, this is a sign there is something binding in the drive train or wheels. There could be a frozen brake caliper or maybe the emergency brake is frozen. I would check this by raising the vehicle and spinning each wheel to see if something is bound. The same thing can be done with the drive train, with the transmission in neutral.

Aside from that, I would inspect the MAF (mass airflow) sensor. They can get dirty and cause many strange symptoms with fords.

There is one other thing that I am wondering about. When you rev the motor in neutral, will it rev all the way to red line, or does it stop before it red lines? It should do this fairly rapidly. If you floor it and it is slow to rev to red line, I suspect you have a clogged exhaust system. You can also check this by feeling how much air is coming out the exhaust pipe. There should be a strong exhaust stream when you rev it up. If the flow isn’t significant, suspect a clogged exhaust.

If you have a clogged exhaust, the main suspect is the catalytic converter.

If you should still need help with this, a YourMechanic expert can come to your home or office and diagnose the slow acceleration issue.

Good luck!

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