Originally Posted by kens97sto171
.......A suggestion might be to do the test with engine cold. Then run the engine up to temp and test again. See what your numbers are......
Recommend you not
pull the plugs on an aluminum head while the engine is hot. Normally, you wait until the engine cools down.
Some additional info to consider:
Pull the fuel pump power and run the engine until it stalls. Pull the Auto Shutdown relay. Pull the coil and one plug per cylinder ('06 or later), then crank over to check compression.
From one aftermarket service manual:
CYLINDER COMPRESSION PRESSURE
The results of a cylinder compression pressure test can be utilized to diagnose several engine malfunctions.
Ensure the battery is completely charged and the engine starter motor is in good operating condition. Otherwise the
indicated compression pressures may not be valid for diagnosis purposes.
1. Clean the spark plug recesses with compressed air.
2. Remove the spark plugs.
3. Secure the throttle in the wide-open position.
4. Disable the fuel system (Refer to 14 - FUEL SYSTEM/FUEL DELIVERY - DESCRIPTION). See section below
5. Remove the Automatic Shutdown (ASD) relay (Refer to 8 - ELECTRICAL/IGNITION CONTROL/AUTO SHUT
DOWN RELAY - REMOVAL).
6. Insert a compression pressure gauge and rotate the engine with the engine starter motor for three revolutions.
7. Record the compression pressure on the 3rd revolution. Continue the test for the remaining cylinders.
8. Refer (Refer to 9 - ENGINE - SPECIFICATIONS) for the correct engine compression pressures
STANDARD PROCEDURE - FUEL SYSTEM PRESSURE RELEASE
Use following procedure if the fuel injector rail is, or is not equipped with a fuel pressure test port.
1. Remove fuel fill cap.
2. Remove fuel pump relay from Power Distribution Center (PDC). For location of relay, refer to label on underside
of PDC cover.
3. Start and run engine until it stalls.
4. Attempt restarting engine until it will no longer run.
5. Turn ignition key to OFF position.
CAUTION: Steps 1, 2, 3 and 4 must be performed to relieve high pressure fuel from within fuel rail. Do not
attempt to use following steps to relieve this pressure as excessive fuel will be forced into a cylinder chamber.
Seems like a cylinder misfire would generate a DTC. Hope this helps you along.