Hesitation, Sag or Stumble

SYMPTOM
Momentary lack of response as the accelerator is pushed down. Can occur at all car speeds. Usually most severe when trying to drive away from a stop. May cause the engine to stall, if severe enough.

NOTE: This symptom may be cause by an accumulation of intake valve deposits and/or clogged fuel injectors.


CAUSE (BY SYSTEM/COMPONENT):

VACUUM HOSES
- Vacuum hoses for splits, kinks, and proper connections, as shown on vehicle emission control label vacuum diagram.

.ENGINE MECHANICAL
- Air leaks at common chamber and intake manifold gaskets

IGNITION SYSTEMS
- Ignition wires for cracks, burned spots or burned ends, hardening, correct firing order, and proper resistance.
- Wiring harness for bare spots, pinches, cuts or corroded connections.
- Ignition timing.
- For open ignition system ground.

FUEL SYSTEMS
- Fuel pressure.
- Water contaminated fuel.
- TPS for binding or sticking.
- Air flow sensor.
- Clogged fuel injectors.

EMISSION SYSTEMS
- Canister purge system for proper operation.
- EGR valve operation.

STARTING AND CHARGING SYSTEM
- Alternator output voltage.