Cylinder Compression Pressure
Check engine mechanical condition with compression gauge, vacuum gauge, or engine analyzer. See engine analyzer manual for specific instructions. For compression specifications, see ENGINE COMPRESSION SPECIFICATIONS table. Install and tighten spark plugs to 11 ft. lbs (15 N.m).
| Application | Specification - psi (kPa) |
|---|---|
| Normal Compression Pressure | (1) |
| Minimum Compression Pressure | (1) |
| Compression Variance | (2) |
| (1) Lowest compression reading should not be less than 70 percent of highest compression reading. No cylinder compression reading should be less than 100 psi (689.5 kPa). (2) Information is not available from manufacturer. | |
| (1) | Lowest compression reading should not be less than 70 percent of highest compression reading. No cylinder compression reading should be less than 100 psi (689.5 kPa). |
| (2) | Information is not available from manufacturer. |
ENGINE COMPRESSION SPECIFICATIONS
Cylinder Combustion Pressure Leakage
- Disconnect negative battery cable. Remove spark plugs. Install Cylinder Head Leakdown Tester (J-35667-A). Measure each cylinder on the compression stroke, with both valves closed.
- Apply air pressure to cylinder leakdown tester. Record the cylinder leakage readings for each cylinder. Normal cylinder leakage is from 12 to 18 percent. Make note of any cylinder with more leakage than the other cylinders. Any cylinder with 30 percent leakage or more requires service.
- Inspect the following primary areas in order to properly diagnose a leaking cylinder. If air is heard from the intake or exhaust system, remove valve rocker arm cover of the suspect cylinder head. Ensure that both valves are closed. Inspect cylinder head for a broken valve spring or remove and inspect suspect cylinder head. If air is heard from the crankcase system at the crankcase oil filler tube, remove piston from suspect cylinder. Inspect piston and connecting rod assembly. Inspect engine block. If bubbles are observed in the radiator, remove and inspect both cylinder heads. Inspect engine block.
- After performing test, remove leakdown tester. Install spark plugs and reconnect negative battery cable.
Exhaust System Backpressure
Before replacing any components, check exhaust system for restrictions. Use vacuum gauge or low-pressure (0-5 psi) gauge to check exhaust system.
If vacuum gauge is used, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Partially open throttle and hold steady. If vacuum gauge reading slowly drops after stabilizing, exhaust system should be checked for restriction. If using low pressure gauge, connect gauge in the following manner
- Check At Oxygen Sensor - Remove oxygen sensor. Install backpressure tester in place of oxygen sensor. After test is completed, coat oxygen sensor threads with anti-seize compound before installation.
Preliminary Checks
Before performing the following tests, check battery condition, engine cranking speed and for adequate fuel in tank. Perform diagnostic system check following any repairs. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS article.
FUEL SYSTEM PRESSURE RELEASE
| WARNING | Remove fuel tank cap and release fuel system pressure before servicing any fuel injection-related components. After releasing fuel system pressure, a small amount of fuel may be released when servicing fuel lines, fuel pump or fuel connections. Cover the fuel system components with a shop towel before disconnection. DO NOT allow fuel to contact engine or electrical components. |
| CAUTION | Fuel system is under pressure. Pressure must be released prior to servicing fuel system. |
Loosen retaining bolt on intake manifold sight shield at top of engine. Remove intake manifold sight shield from top of engine. Disconnect negative battery cable. Loosen fuel filler cap. Install Fuel Pressure Gauge Fitting Adapter (J-34730-262) to fuel pressure test port connection. Install Fuel Pressure Gauge (J-34730-1A) to fuel pressure gauge fitting adapter on fuel rail. Wrap a shop towel around pressure connection when installing fuel pressure gauge to absorb fuel leakage. Place gauge bleed hose into an approved gasoline container. Open bleed valve to release fuel pressure.
IGNITION SYSTEMS
Note. For additional ignition system and component diagnosis, see IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - 3.4L AZTEK & RENDEZVOUS article.
CAMSHAFT POSITION SENSOR
For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS article.
CRANKSHAFT POSITION SENSOR
For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS article.
Scheme 1
Scheme 2
Scheme 3
IGNITION RELAY
See IGNITION RELAY under MODULES, MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING - 3.4L AZTEK & RENDEZVOUS article.
IDLE SPEED & IGNITION TIMING
Idle speed and ignition timing are controlled by PCM. Incorrect idle speed are normally caused by dirty throttle plate or vacuum leaks. Ensure all vacuum components are functioning properly.
AZTEK
For wiring diagrams, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
RENDEZVOUS
For wiring diagrams, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.