This procedure adjusts the valve lash (clearance) on the 2014-2019 Toyota Corolla 1.8L I4 engine to maintain proper valve timing and prevent excessive noise or engine damage.

Warnings

Tools required

Parts

• Valve cover gasket × 1 — Use OEM specification
• Valve cover grommet seals × 4 — Use OEM specification
• PCV valve grommet × 1 — Use OEM specification

Preparation

1. Ensure engine is completely cold (coolant at ambient temperature)
2. Disconnect negative battery terminal and wait 90 seconds for airbag system to deplete
3. Remove engine cover by pulling upward on retaining clips
4. Remove air intake tube and air filter housing assembly
5. Disconnect ignition coil connectors and remove all four ignition coils
6. Remove spark plugs and store in order for reinstallation

Procedure

1. 1

   Remove valve cover
   Disconnect PCV hoses and breather hoses from valve cover. Label any vacuum lines for reinstallation. Remove valve cover bolts in reverse sequence (start from outside, work inward). Carefully lift valve cover off cylinder head, tapping gently with rubber mallet if stuck. Inspect gasket surfaces for damage.
   Torque spec

   Cover Bolts15 Nm (11 lb-ft)
2. 2

   Position crankshaft to TDC cylinder #1
   Rotate crankshaft clockwise using breaker bar on crankshaft pulley bolt until timing marks on crankshaft gear and camshaft gears align with their respective marks on the timing chain cover and cylinder head. Verify cylinder #1 is at TDC compression stroke (both intake and exhaust cam lobes pointing upward/away from valves).
   ⚠Always rotate engine in clockwise direction only when viewing from front of vehicle
3. 3

   Measure valve clearance - cylinder #1
   With cylinder #1 at TDC, measure valve clearance on cylinder #1 intake and exhaust valves using feeler gauge between camshaft lobe base circle and valve lifter. Insert feeler gauge; it should slide with slight drag. Record measurements. Intake specification: 0.15-0.25mm. Exhaust specification: 0.25-0.35mm.
   ℹ️Measure clearance when cam lobe is pointing directly away from valve (on base circle)
4. 4

   Measure valve clearance - cylinder #2
   Rotate crankshaft clockwise 180 degrees (one-half turn). Cylinder #2 exhaust and cylinder #3 intake valves are now measurable. Use feeler gauge to measure and record clearances on these valves. Compare to specifications.
5. 5

   Measure valve clearance - cylinder #4
   Rotate crankshaft clockwise another 180 degrees (360 degrees total from start). Measure and record valve clearances for cylinder #4 intake and exhaust valves. Compare to specifications.
6. 6

   Measure valve clearance - cylinder #3
   Rotate crankshaft clockwise another 180 degrees (540 degrees total from start). Measure and record valve clearances for cylinder #3 exhaust and cylinder #2 intake valves. Compare to specifications. You now have measurements for all 8 valves.
7. 7

   Adjust out-of-specification valves
   For each valve outside specification, rotate crankshaft to position that specific cam lobe pointing away from valve. Using 14mm wrench to hold the adjusting screw, loosen the lock nut with another wrench. Turn adjusting screw clockwise to decrease clearance or counterclockwise to increase clearance. Recheck clearance with feeler gauge and adjust as needed.
   ⚠Must hold adjusting screw stationary while tightening lock nut to prevent clearance change
   Torque spec

   Valve Lash Adjusting Screw Lock Nut20 Nm (15 lb-ft)
8. 8

   Verify all adjustments
   After tightening each lock nut to specification, re-measure valve clearance to confirm it remains within specification. The clearance may change slightly when lock nut is torqued. Readjust if necessary. Repeat verification process for all adjusted valves by rotating crankshaft through complete cycle.
9. 9

   Clean and prepare gasket surfaces
   Clean valve cover and cylinder head gasket surfaces thoroughly with plastic scraper and clean rag. Remove all old gasket material and oil residue. Inspect surfaces for warping or damage. Do not use metal scrapers that could gouge aluminum surfaces.
   ⚠Ensure no debris falls into engine; cover open valve train with clean shop towels during cleaning
10. 10

    Install new valve cover gasket
    Install new valve cover gasket into groove on valve cover. Replace all grommets and seals including PCV valve grommet. Ensure gasket is seated properly in groove all the way around. Apply small amount of engine oil to gasket surface that contacts cylinder head.
11. 11

    Install valve cover
    Carefully position valve cover onto cylinder head, ensuring gasket remains in place. Install valve cover bolts finger-tight. Tighten valve cover bolts to specification in proper sequence: start at center bolts and work outward in spiral pattern. Use torque wrench set to 10 Nm (7 lb-ft).
    ⚠Tighten in multiple passes (50% torque, then 100%) in proper sequence to prevent gasket distortion
    Torque spec

    Cover Bolts15 Nm (11 lb-ft)
12. 12

    Reinstall components
    Reinstall spark plugs to their original cylinders. Reinstall ignition coils and connect electrical connectors. Reinstall air filter housing and intake tube. Reconnect all vacuum hoses and PCV hoses to original positions. Reinstall engine cover.

Reassembly

1. Reconnect negative battery terminal and perform window initialization if equipped with auto up/down
2. Double-check all electrical connectors are fully seated
3. Verify no tools or rags were left in engine bay

Verification

• Start engine and listen for abnormal valve train noise (ticking or tapping)
• Allow engine to reach operating temperature and verify no oil leaks from valve cover
• Engine should run smoothly without misfires or rough idle
• Perform test drive and verify normal engine performance across RPM range

More procedures for this vehicle