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1999 Mercury Mystique Car Bucking and Jerking

Tiny
BIANCA1223
  • MEMBER
  • 1999 MERCURY MYSTIQUE
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 206,023 MILES
Our car while driving bucks and jerks on or off the accelerator most of the time while on. It will thrust the car forward, never acts as though it will die, but it jerks and jerks and then eventually stops after a while and may act up again depending on how long you drive it. You never know when it's going to do it, one way to know though is that the rpms go way up even if you're only going 25 miles an hour, then goes back up and down until it eventually stops. Someone mentioned the torque converter but than someone said it couldn't be. Any clue?
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Tuesday, June 2nd, 2009 AT 6:19 PM

1 Reply

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
1999 Mercury Mystique Car Bucking and Jerking

Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires
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Tuesday, June 2nd, 2009 AT 6:40 PM

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