HESITATION, SAG, STUMBLE
This is defined as a momentary lack of response as the accelerator is pushed down. It can occur at all vehicle speeds. Usually it is most severe when first trying to make car move, as from a stop sign. Condition may be severe enough to cause vehicle to stall.
Possible cause & correction
• Check for proper operation of thermostatic air cleaner.
• Check for proper EFE operation.
• Check for correct fuel pressure of 9-12 psi in all speed ranges. Also check for contaminated fuel.
• Check vacuum hose to MAP sensor for leaks or restrictions, and restrictions at MAP port on throttle body: Tee vacuum gauge into MAP hose at sensor. Gauge reading and parameter value (.0.2/ P.0.2) should be about the same and respond quickly to changes in engine load.
• Check for fouled, cracked, or defective spark plugs or spark plug wires.
• Check for correct PROM number (parameter .1.3/P.1.3).
• Check TPS for binding or sticking.
• Check ignition timing.
• Check for proper operation of EGR system.
• Check fuel injectors: With injector connectors disconnected, check for fuel leakage from injectors while cranking. Reconnect injector connectors. Also check injector spray patterns.
• Check for open in HEI ground circuit.
• Check for proper operation of canister purge system.
• Check for carboned, or sticking valves.
• Check for restricted exhaust and catalytic converter.
© 2008 Mitchell Repair Information Co., LLC.
Dec 21, 2010 at 5:46 AM
