Hesitation, Sag, Stumble

DEFINITION

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.

Perform careful visual (physical) check.
CHECK:
- Vacuum hoses for splits, kinks, and proper connections, as shown on vehicle emission control label vacuum diagram.
- Air leaks from intake duct, common chamber or intake manifold gaskets.
- Ignition wires for cracks, burned spots or burned ends, hardening, correct firing order, and proper resistance (no more than 30K Ohms per wire).
- Wiring harness for bare spots, pinches, cuts or corroded connections.

CHECK:
- Fuel pressure.
- Water contaminated fuel.
- TPS for binding or sticking.
- Ignition timing. See Vehicle Emission Control Information label.
- Air flow sensor for sticking or improper air bypass adjustment.
- Alternator output voltage. Repair if less than 9 or more than 16 volts.
- For open ignition system ground.
- Canister purge system for proper operation.
- EGR valve operation.
- Perform injector balance test.