Kia Optima: Repair procedures - General Information - Engine Mechanical System - Kia Optima TF 2011-2024 Service ManualKia Optima: Repair procedures

If the there is lack of power, excessive oil consumption or poor fuel economy, measure the compression pressure.
1. Warm up and stop engine.

Allow the engine to warm up to normal operating temperature.

2. Disconnect the injector extension connector (A) and ignition coil connectors (B).

3. Remove ignition coils (A).

4. Remove spark plugs.

Using a 16mm plug wrench, remove the 4 spark plugs.

5. Check cylinder compression pressure.
(1) Insert a compression gauge into the spark plug hole.

(2) Fully open the throttle.
(3) While cranking the engine, measure the compression pressure.
Always use a fully charged battery to obtain engine speed of 200 rpm or more.
(4) Repeat steps (1) through (3) for each cylinder.
This measurement must be done in as short a time as possible.

Compression pressure :

1078 kPa (11.0 kgf/cm², 156 psi) / 200 ~ 250 rpm

Minimum pressure :

931 kPa (9.5 kgf/cm², 135 psi)

Difference between each cylinder :

100kPa (1.0kgf/cm², 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.
A. If adding oil helps the compression, it is likely that the piston rings and/or cylinder bore are worn or damaged.
B. If pressure stays low, a valve may be sticking or seating is improper, or there may be leakage past the gasket.
6. Reinstall spark plugs.
7. Install ignition coils.
8. Connect the injector extension connector and ignition coil connectors.
9. Some DTC's may exist after the inspection test and may need to be manually cleared with GDS.
Valve Clearance Inspection And Adjustment
Inspect and adjust the valve clearance when the engine is cold (Engine coolant temperature : 20C (68F)) and cylinder head is installed on the cylinder block.
In case of removing the high pressure fuel pump, high pressure fuel pipe, delivery pipe, and injector, there may be injury caused by leakage of the high pressure fuel. So dont do any repair work right after engine stops.
1. Remove the cylinder head cover. (Refer to Timing system in this group)
2. Set No.1 cylinder to TDC/compression.
(1) Turn the crankshaft pulley and align its groove with the timing mark "T" of the lower timing chain cover.

(2) Check that the TDC marks (A) of the CVVT sprockets are in straight line on the cylinder head surface as shown in the illustration.

If not, turn the crankshaft one revolution (360)

3. Inspect the valve clearance.
(1) Check only the valve indicated as shown. Measure the valve clearance.

A. Using a thickness gauge, measure the clearance between the tappet and the base circle of camshaft.
B. Record the out-of-specification valve clearance measurements. They will be used later to determine the required replacement adjusting tappet.

Valve clearance


Engine coolant temperature : 20C [68F]


Intake : 0.10 ~ 0.30mm (0.0039 ~ 0.0118in.)

Exhaust : 0.20 ~ 0.40mm (0.0079 ~ 0.0157in.)

(2) Turn the crankshaft pulley one revolution (360) and align the groove with timing mark "T" of the lower timing chain cover.
(3) Check only valves indicated as shown. Measure the valve clearance.

4. Adjust the intake and exhaust valve clearance.
(1) Set the No.1 cylinder to the TDC/compression.
(2) Mark the timing chains (A) on the timing marks of the CVVT sprockets.

(3) Remove the front camshaft bearing cap.
(4) Turn the crankshaft pulley 15 clockwise.
(5) Remove the service hole bolt(A) of the timing chain cover.

The bolt must not be reused once it has been assembled.
(6) Remove the intake and exhaust camshaft bearing caps.
(7) Release the ratchet of the timing chain tensioner by pulling the link down using a thin rod.

(8) After loosening the timing chain, remove the exhaust CVVT & camshaft assembly (A) and then the intake CVVT & camshaft assembly (B).

When disconnect the timing chain from the CVVT sprocket, hold the timing chain.
(9) Tie down timing chain so that it doesn't move.
Be careful not to drop anything inside timing chain cover.
(10) Measure the thickness of the removed tappet using a micrometer.

(11) Calculate the thickness of a new tappet so that the valve clearance comes within the specified value.

Valve clearance [Engine coolant temperature : 20C(68F)]

T : Thickness of removed tappet

A : Measured valve clearance

N : Thickness of new tappet

Intake : N = T + [A - 0.20mm (0.0079in.)]

Exhaust : N = T + [A - 0.30mm (0.0118in.)]

(12) Select a new tappet with a thickness as close as possible to the calculated value.
Shims are available in 47 size increments of 0.015mm (0.0006in.) from 3.00mm (0.118in.) to 3.690mm (0.1452in.)
(13) Place a new tappet on the cylinder head.
(14) Hold the timing chain, and place the intake CVVT & camshaft assembly.
(15) Place the exhaust CVVT & camshaft assembly after releasing the ratchet of the timing chain tensioner.
The timing marks of each CVVT sprocket should be matched with timing marks (painted link) of timing chain when installing the timing chain.

(16) Install the camshaft bearing caps in their proper locations.

Tightening order

Group A → Group B → Group C

Tightening torque

Step 1

M6 : 5.9N.m (0.6kgf.m, 4.3lb-ft)

M8 : 14.7N.m (1.5kgf.m, 10.8lb-ft)

Step 2

M6 : 10.8 ~ 12.7N.m (1.1 ~ 1.3kgf.m, 8.0 ~ 9.4lb-ft)

M8 : 27.5 ~ 31.4N.m (2.8 ~ 3.2kgf.m, 20.3 ~ 23.1lb-ft)

(17) Install the service hole bolt (A).

Tightening torque :

11.8 ~ 14.7N.m (1.2 ~ 1.5kgf.m, 8.7 ~ 10.8lb-ft)

(18) Turn the crankshaft two turns in the operating direction (clockwise), and then check that the TDC marks (A) of the CVVT sprockets are in straight line on the cylinder head surface.

(19) Recheck the valve clearance.

Valve clearance [Engine coolant temperature : 20C(68F)]


Intake : 0.17 ~ 0.23mm (0.0067 ~ 0.0090in.)

Exhaust : 0.32 ~ 0.38mm (0.0126 ~ 0.0150 in.)

(20) Install the cylinder head cover. (Refer to Timing system in this group)

Description Specifications Limit General Type In-line, DOHC   Number of cylinders ...

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