Car losing power

2011 MERCURY MARQUIS
80,000 MILES • 4.6L • V8 • 2WD • AUTOMATIC
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MGM11
  • MEMBER
  • 1 POST
Hello,

My car lunches pretty good and drives fresh until I reach twenty km/h or so. Then the car starts to drive slower. The car feels strong but drives slow. At 1500 rpm I used to reach ninety km/h. Now I cannot get to seventy km/h with 1500 rpm. I changed fuel filter 6,000 miles ago. I changed spark plugs and cleaned the throttle body. The intake filter is clean. There is a tiny unstable vibration feeling on the car chassis. Fuel injectors are working. And I cannot seem to find out why is this happening. P.S there is no check engine light.

Regards,
Hani
Apr 2, 2018 at 9:36 PM
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ASEMASTER6371
  • AUTOMOTIVE REPAIR CONTRIBUTOR
  • 52,796 POSTS
Good morning.

It sounds like you have a clogged catalytic converter. when the engine cannot breathe from a restriction, it will not produce power.

A shop can confirm by doing a back pressure test by removing the O2 sensor and inserting a gauge into the hole and measuring that pressure.

Roy
Apr 3, 2018 at 4:22 AM