1998 Chevy Truck Runs rough

BUCKINOFF78

MEMBER
1998 CHEVROLET TRUCK
V8
4WD
AUTOMATIC
166,000 MILES

I have a 98 Chevy 4x4 2500 truck. Replace the engine about 9000 miles ago. I replaced all the sensors on the motor, then the truck started to run rough. Ran all the codes the truck threw. The truck at 2000 rpm range feels like you're pulling a heavy trailer it jerks while at cruising speed. I ran a DTC scanner on it an nothing showed up so I replaced the plug wires. Then a MAS code low voltage signal came up, replace the MAS sensor. Still runs rough. Almost like its detonating, doesn't do it under exceleration.

Sunday, November 15th, 2009 AT 12:52 PM

2 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Check the following:

Oxygen sensor
Catalytic converter
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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Sunday, November 15th, 2009 AT 3:17 PM

BUCKINOFF78

MEMBER
2 POSTS

Thanks for the suggestions. I have replaced:
Map sensor
Mas sensor
throttle position sensor
Fuel pressure reg.
Fuel pump
Cleaned injectors when I replaced engine
Cam sensor
Crank sensor
Knock sensor
Fuel filter
I wondered about the O2 sensor and the Catalytic converters. I thought if the O2 sensor went bad then I would get a DTC. I will pull the plugs and check them, thanks for the help.

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Sunday, November 15th, 2009 AT 3:59 PM