1994 GMC Jimmy engine hesitation at low speed

SHANES76

MEMBER
1994 GMC JIMMY

Engine Performance problem
1994 GMC Jimmy 6 cyl Four Wheel Drive Automatic

I have a 4.3 Vortec with VIN"W" and it like right off idle and a low speed until it shifts into 2nd there is a hesitation and while coasting the idle surges- it doesnt stall out though- it has a new MAP sensor, intake air temperature sensor(got a SES for it) But if I drive it for about an hour on the highway and stop at a light and take off sometimes it wont hestitate until a few stops, it was really bad but I pulled the IAC valve and cleaned it, check EGR which one side was loose so I cleaned it - reinstalled with new gasket, new PCV valve. I am getting a SES for 35 (IAC valve and 43(knock sensor) the knock sensor is not hooked up due to a broken plug would these 2 items cause my problems? It starts great, idles great- might have a little pop every once in a while

2 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Check and test the following below:

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
Coil and Rotor