2004 Toyota 4Runner Engine running rough

2004 TOYOTA 4RUNNER
94,000 MILES • 6 CYL • 4WD • AUTOMATIC
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MCL
  • MEMBER
  • 1 POST
Hello-

I have a 04 Toyota 4Runner with a V6. It has 94k miles on it an has just had it's 90k tune. Upon acceleration the engine stuters or runs rough and the check engine light comes on. The VSC lights come on as well. Upon further acceleration it will smooth out and rough again like it's missing. At idle it will run smoothly 95% of the time with an occasional miss.

What do you guys think is the culprit?
Oct 13, 2009 at 1:22 PM
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RASMATAZ
  • ✓Experienced Mechanic
  • 75,988 POSTS
Could be caused by one of the following:

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
Oct 13, 2009 at 1:28 PM
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