Lack of Power/Sluggish/Spongy/Stumble

Definition: Engine delivers less than expected power. Little or no increase in speed when accelerator pedal is pushed down part way.
- Compare customer's vehicle to similar unit. Make sure the customer's vehicle has an actual problem.
- Remove air cleaner and check air filter for dirt, or for being plugged. Replace as necessary.
- If there is spray from only one injector, then, there is a malfunction in the injector assembly, or in the signal to the injector assembly. The malfunction can be isolated, by switching the injector connectors. If the problem remains with the original injector, after switching the connector, the injector is defective. Replace the injector. If the problem moves with the injector connector, the problem is an improper signal in the injector circuit, see CHART A-3. Related Tests, Information and Procedures
- CHECK:
- Ignition timing. See "Vehicle Emission Control Information" label.
- For restricted fuel filter, contaminated fuel or improper fuel pressure. See CHART A-6. Chart A-6 Fuel System Pressure Test
- ECM grounds. Refer to wiring.
- Injector wires for short to ground at Air Cleaner.
- EGR operation for being open or partly open all the time.
- Generator output voltage.Repair if less than 9 or more than 16 volts.
- Engine valve timing and compression.
- Engine for proper or worn camshaft.
- Transmission torque converter operation.
- Secondary ignition voltage, using a scope or ST-125.
- Proper operation of EST.
- CHECK EXHAUST SYSTEM FOR RESTRICTION:
1. With engine at normal operating temperature, connect a vacuum gage to any convenient vacuum port on intake manifold.
2. Run engine at 1000 rpm and record vacuum reading.
3. Increase rpm slowly to 2500 rpm. Note vacuum reading at steady 2500 rpm.
4. If vacuum at 2500 rpm decreases more than 3", from reading at 1000 rpm, the exhaust system should be inspected for restrictions.
5. Disconnect exhaust pipe from engine and repeat steps 3 & 4. If vacuum still drops, more than 3" with exhaust disconnected, check valve timing.