1995 GMC Sierra

MIKE CONNALLY

MEMBER
1995 GMC SIERRA
V8
4WD
AUTOMATIC
17,900 MILES

Engine starts fine hot or cold. When engine is not at full opperating temp runs fine. NO miss or stumble. When engine has reached opperating temp it has hesitation and off idle multiple miss or stumbling while held at off idle. I can smell gas fume at the exhaust in this condition. No engine trouble code. The code light does work.

Monday, January 19th, 2009 AT 2:24 PM

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

Engine hesitation could be caused by 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

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