1991 Toyota 4Runner Hesitates under acceleration

Tiny
JON PATRICK
  • MEMBER
  • 1991 TOYOTA 4RUNNER
  • 6 CYL
  • 4WD
  • MANUAL
  • 300,000 MILES
Hi there. I recently bought a 4 runner with a stuffed engine, I rebuilt the 3VZE V6 engine spent alot of money on various parts including suspention. The problem is very intermitent which is why im having trouble finding the problem & really need some help and is driving me mad. Sometimes when I accellerate the engine holds back unless I floor it then it clears for a while then comes back, can do it on the hwy or off traffic lights. Feels like something is breaking down, or starving for something, fuel pressure is good plenty, new plugs, leads, coil, no fault codes showing. When it clears it runs really good, responsive but when it hesitates its bad like its out of fuel but its not. Please can some one help me with this as im really stuck. Thank you
Monday, January 18th, 2010 AT 7:36 AM

1 Reply

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

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
Cap and Rotor
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Monday, January 18th, 2010 AT 7:54 AM

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