1999 GMC Yukon hesitates

Tiny
RAZORSMITH42
  • MEMBER
  • 1999 GMC YUKON
  • V8
  • 2WD
  • AUTOMATIC
  • 90,000 MILES
When accelerating, the truck hesitates then jumps, hesitates then jumps. It seems to even out after getting up to about 40mph or so. It also seems to be worse after a rain. We just had the fuel pump replaced and the distributor wires and plugs replaced a year ago.
Saturday, July 5th, 2008 AT 4:58 PM

1 Reply

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Possible Causes of Engine Hesitation

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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Saturday, July 5th, 2008 AT 8:08 PM

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