Lack of Power/Sluggish/Spongy/Stumble

LACK OF POWER, SLUGGISH, OR SPONGY
Definition: Engine delivers Less than expected power. Little or no increase in speed, when accelerator pedal is partially applied.

IMPORTANT PRELIMINARY CHECKS
Before using this section you should have performed the "On-Board Diagnostic System Check" - Powertrain/On-Board Diagnostic System Check and determined that:
1. The control module and MIL (Service Engine Soon) are operating correctly.
2. There are no diagnostic trouble codes stored, or there is a diagnostic code but no MIL (Service Engine Soon).
^ Several of the following symptom procedures call for a careful visual/physical check. The importance of visual/physical checks cannot be over stressed. because they can lead to correcting a problem without further checks and can save valuable time.

VISUAL / PHYSICAL CHECK
This check should include:
^ Control module grounds for being clean, tight, and in their proper location.
^ Vacuum hoses for splits, kinks and proper connections, as shown on "Vehicle Emission Control Information" label Check thoroughly for any type of leak or restriction.
^ Air leaks at all mounting areas of the intake manifold sealing surfaces.
^ Ignition wires for cracking, hardness, proper routing, or carbon tracking.
^ Wiring for proper connections, pinches, and cuts.
^ The following symptom charts contain groups of possible causes for each symptom and cover several engines. These procedures are not necessarily meant to be done in consecutive order. If Tech 1 scan tool readings do not indicate the problems, then proceed in a logical order, easiest to check or most likely cause first. To determine if a particular system or component is used on a specific vehicle, refer to the "Electronic/Powertrain Control Module (ECM/PCM)" Wiring Diagrams for application. Electronic/Powertrain Control Module (ECM/PCM)

^ Compare customer's vehicle with a similar unit. Make sure the customer has an actual problem.
^ Remove air filter and check for dirt, or for being plugged, replace as necessary.
^ Transmission shift pattern and down shift operation.
^ If there is spray from only one injector on the TBI unit, then, there may be 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 circuits. Refer to "CHART A-3".

FUEL SYSTEM
^ CHECK: For contaminated fuel.
^ CHECK: For restricted fuel filter, contaminated fuel or improper fuel pressure. Refer to "CHART A-6". Related Tests, Information and Procedures

IGNITION SYSTEM
^ CHECK: Proper ignition voltage output with spark tester J 26792 or equivalent (ST-125).
^ CHECK: Ignition timing and proper operation of ignition control. Ignition System Check

EXHAUST SYSTEM
^ CHECK: Exhaust system for possible restriction. Inspect exhaust system for damaged or collapsed pipes. Inspect muffler for heat distress or possible internal failure.
1. With engine at normal operating temperature, connect a vacuum gage to any convenient vacuum port on intake manifold.
2. Operate engine at 1000 RPM and record vacuum reading.
3. Increase RPM slowly to 2500 RPM. Note vacuum reading at a steady 2500 RPM.
4. If vacuum at 2500 RPM decreases more than 10 kPa (3" Hg) from reading at 1000 RPM, the exhaust system should be inspected for restrictions.
5. Disconnect exhaust pipe from engine and repeat Steps 3 and 4. If vacuum still drops more than 10 kPa (3" Hg) with exhaust disconnected, check for exhaust manifold restriction and valve timing.

ADDITIONAL CHECKS
^ CHECK: Control module grounds for being clean, tight, and in their proper location.
^ CHECK: EGR operation for being open or partly open all the time. Testing and Inspection
^ CHECK: Torque Converter Clutch (TCC) operation. Description and Operation
^ CHECK: A/C operation. Refer to "A/C Chart". Functional Test/Check
^ CHECK: Generator output voltage. Repair if less than 9 or more than 16 volts.

ENGINE MECHANICAL
^ CHECK: Engine compression, valve timing, and for proper or worn camshaft.