Kia Optima: Compression Test - Engine Mechanical SystemKia Optima: Compression Test

Compression Pressure Inspection
   
   
If the there is lack of power, excessive oil consumption or poor fuel economy, measure the compression pressure.
   
   
Engine may start anytime the vehicle is in READY mode.1. Warm up and stop engine.
1.
Warm up and stop engine.
Allow the engine to warm up to normal operating temperature.
2.
Remove the engine cover.
3.
Disconnect the injector connectors (A).


4.
Disconnect the ignition coil connectors (A).


5.
Remove ignition coils (A).


6.
Remove spark plugs.
Using a 16mm plug wrench, remove the 4 spark plugs.
7.
Check cylinder compression pressure.
(1)
Insert a compression gauge into the spark plug hole. If possible, place the gauge where it can be seen from inside the vehicle.


(2)
Attach the GDS
Connect the cable of GDS to the data link connector.
Select the vehicle model and then the HCU system.
Select the "Engine On Test". See the screens below.
(3)
While cranking the engine, measure the compression pressure.
With the Brake pedal depressed, press the Start/Stop Button (SSB) one time.
If the engine cranks, let it crank about 8 to 10 cycles (until the gauge readings stabilizes) then press the SSB one time to stop the engine from cranking.
If the engine does not crank on its own when the SSB is pressed, the GDS should be used to crank the engine. While in the “Engine On Test” follow the instruction on the screen.
The “Engine On Test” will start the engine cranking. After the compression readings stabilize (8-10 cycles), press the SSB one time to stop the cranking.


(4)
Repeat steps (1) through (3) for each cylinder.
   
   
Be sure ignition is in the OFF mode between each cylinder test.
This measurement must be done while the engine is still near operating temperature.

Compression pressure :
1,283kPa (13.0kgf/cm?, 185psi) / 200 ~ 250rpm
Minimum pressure :
1,135kPa (11.5kgf/cm?, 164psi)
Difference between each cylinder :
100kPa (1.0kgf/cm?, 15psi) or less

(5)
If the cylinder compression in 1 or more cylinders is low, pour a small amount of engine oil into the cylinder through the spark plug hole and repeat steps (1) through (3) for cylinders with low compression.
If adding oil helps the compression, it is likely that the piston rings and/or cylinder bore are worn or damaged.
If pressure stays low, a valve may be sticking or seating is improper, or there may be leakage past the gasket.
8.
Reinstall spark plugs.
9.
Install ignition coils.

Tightening torque:
3.9 ~ 5.9N.m (0.4 ~ 0.6kgf.m, 2.9 ~ 4.3lb-ft)

10.
Connect the injector connectors and ignition coil connectors.
11.
Some DTC''s may exist after the inspection test and may need to be manually cleared with GDS.
Specifications
Specifications DescriptionSpecificationsLimitGeneralTypeIn-line, DOHC?Number of cylinders4?Bore88mm (3.464in.)?Stroke97mm (3.819in.)?Total displacement2359cc (143.90cu.in)?Compression ratio13.0 ...

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