2001 Chevy Venture Hesitating Engine

AXFRADETTE

MEMBER
2001 CHEVROLET VENTURE
6 CYL
FWD
AUTOMATIC
163,000 MILES

Only in the morning when van first starts, engine will not run smoothly, will hesitate and when apply pressure to gas pedal, engine will hesitate. Almost seems like catalytic converter clogged. Has same symptoms but I know that is not it because when car warms up, it runs fine. Already changed fuel pump. Was not the cause. Have 3 error codes as follows

P1374- 3x reference circuit
P0171- fuel trim system lean (bank 1)
P0420- catalyst system low efficiency

I have done extensive research on these codes and know that either
**my o2 sensor could be dirty/damaged
**mass air flow sensor dirty

please help? I read about people in exact same situation that spent $2000 to fix vehicle and was only a $100 problem at the end.

3 Replies

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