1999 GMC C1500 engine misses

MX647

MEMBER
1999 GMC C1500
V8
4WD
AUTOMATIC
205,000 MILES

I just had a fuel pump go bad, I replaced it and it fixed the problem. But now it misses, it doesnt seem to miss at idle or when taking off while pressing lightly on the gas pedal. But when it shifts in to 3 gear it start to miss or it is at that time it is noticable. Also under hard acceleration in any gear. So then I also changed the fuel filter, spark plugs and wires and none of this has made a difference. It ran fine before I had to replace the fuel pump. Thanks for any help

Wednesday, November 11th, 2009 AT 7:34 PM

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

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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Wednesday, November 11th, 2009 AT 8:46 PM