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2005 Kia Optima RPMs up and down, car jerks

Tiny
LLG6678
  • MEMBER
  • 2005 KIA OPTIMA
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 76,000 MILES
Just bought used Kia Optima 4 weeks ago. 76,000miles. After 2 weeks the car started jerking and you have to push the gas pedal down all the way to get it up to 20mph. After that the car jerks and jerks until it finally gets to 40-50mph then seems fine (for a few miles0. But when you come to redlight it feels like car is going to shut off and sometimes does. You have to put it in park and rev up engine to stop it from cutting off. Had new computer and spark plugs done. 2 Kia dealerships stumped. Want to now charge $800 to go under the hood.
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Tuesday, August 18th, 2009 AT 5:09 PM

1 Reply

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check the following:

Oxygen sensor
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, August 18th, 2009 AT 5:28 PM

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