1999 GMC Suburban multiple cylinder missfires

JASON.BRIGHT

MEMBER
1999 GMC SUBURBAN
V8
2WD
AUTOMATIC
190,000 MILES

Hi ive done everything spark plugs, the wires, distrubutor cap, and rotor button. Ive had it placed on a scanner and it pulled up 24000 misfires on cyl 5 and 75000 on seven. My truck only misfires when it starts to raise temp. And it almost has like a gurgling in the exhaust. Ive had a pressure test done on the coolant side and it didnt show any leaks in the cylinders. Please help me before I dump too much money into people trying to figure out what it really is thanks.
Jason Bright

3 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Engine misfiring can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

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Sunday, January 31st, 2010 AT 11:44 AM

JASON.BRIGHT

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6 POSTS

Well it accelorates fine when I get on the gas but missfires at low to midrange rpm

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Sunday, January 31st, 2010 AT 5:35 PM

RASMATAZ

MECHANIC
75,992 POSTS

Check and test all 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)
Dirty or worn spark plugs
Bad plug wires
Weak ignition coil

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Sunday, January 31st, 2010 AT 5:45 PM