Intake Manifold

Remove and replace the intake manifold on a 2016-2021 Honda Civic 1.5L turbo engine, including disconnection of all sensors, hoses, and fuel system components.

Warnings

Tools required

Parts

• Intake manifold gasket × 1 — Use OEM Honda specification
• Throttle body gasket × 1 — Use OEM Honda specification
• PCV valve o-ring/seal × 1 — Use OEM Honda specification
• Vacuum hose clamps (assorted) × 1 — Replace any damaged clamps

Fluids

• Honda Type 2 Coolant (Blue) — 1 qt

Preparation

1. Ensure engine is completely cold (wait at least 3 hours after last operation)
2. Park vehicle on level ground and engage parking brake
3. Disconnect negative battery terminal and wait 3 minutes for systems to discharge
4. Remove engine cover by pulling upward on front clips
5. Take photos of all vacuum hose routing, electrical connections, and harness positions for reference
6. Place drain pan under vehicle to catch any coolant spillage

Procedure

1. 1

   Relieve fuel system pressure
   Remove the fuel pump relay from the under-hood fuse box (relay location marked in owner's manual). Attempt to start the engine and let it run until it stalls. Crank for 3-5 seconds after stalling to ensure pressure is relieved. Reinstall fuel pump relay after procedure.
   ⚠️Have a fire extinguisher nearby when working with fuel system components
2. 2

   Remove air intake system
   Loosen the clamp at the turbo inlet and disconnect the air intake tube. Remove the air filter box by removing mounting bolts and disconnecting the MAF sensor electrical connector. Remove the entire intake tube assembly from turbo to air box. Set aside in clean area.
3. 3

   Disconnect throttle body and associated components
   Disconnect the throttle body electrical connector by pressing the release tab. Remove the four throttle body mounting bolts and carefully remove throttle body from intake manifold. Leave coolant hoses attached to throttle body if possible, or drain coolant and disconnect hoses if necessary.
   Torque spec

   Throttle Body Bolts10 Nm (7 lb-ft)
4. 4

   Disconnect fuel system components
   Disconnect the fuel line from the fuel rail using appropriate fuel line disconnect tool. Have shop towels ready to catch residual fuel. Remove the fuel rail mounting bolts and carefully lift fuel rail with injectors attached away from intake manifold. Secure fuel rail assembly to prevent strain on fuel line. Cover injector ports with clean shop towels to prevent debris entry.
   ⚠Do not allow dirt or debris to enter fuel injector ports or fuel rail
   Torque spec

   Fuel Rail Bolts12 Nm (9 lb-ft)
5. 5

   Disconnect vacuum lines and PCV system
   Disconnect the brake booster vacuum line from the intake manifold. Remove the PCV valve by twisting counterclockwise and pulling from the valve cover. Disconnect all small vacuum lines from the intake manifold, including purge valve line and any additional emission control vacuum lines. Reference photos taken during preparation.
   Torque spec

   PCV Valve8 Nm (6 lb-ft)
6. 6

   Disconnect intake manifold sensors
   Disconnect the MAP sensor electrical connector located on the intake manifold. Disconnect any other sensors mounted to the intake manifold (EVAP purge valve, vacuum switching valves). Press release tabs and gently wiggle connectors free without pulling on wires.
7. 7

   Remove intake manifold support bracket
   Locate the support bracket connecting the intake manifold to the engine block or cylinder head. Remove the mounting bolts securing this bracket. The bracket may be located on the passenger side or underneath the manifold depending on production date.
   Torque spec

   Mounting Bolts45 Nm (33 lb-ft)
8. 8

   Remove intake manifold mounting bolts
   Remove all intake manifold mounting bolts in reverse order of tightening sequence (outside-in pattern). There are typically 6-8 bolts securing the manifold to the cylinder head. Keep bolts organized by location if they are different lengths. Note the location of any ground wires or brackets attached to manifold bolts.
   ℹ️Some bolts may be hidden under wiring harnesses or hoses
   Torque spec

   Intake Manifold Bolts25 Nm (18 lb-ft)
9. 9

   Remove intake manifold
   Carefully lift the intake manifold away from the cylinder head. The manifold may be stuck due to gasket adhesion - gently work it free using a twisting motion, but never pry between sealing surfaces. Once free, cover the cylinder head intake ports with clean shop towels to prevent debris entry.
10. 10

    Clean gasket surfaces
    Using a plastic scraper or wire brush, carefully remove all old gasket material from both the cylinder head and intake manifold mating surfaces. Do not gouge or scratch the aluminum surfaces. Clean surfaces thoroughly with brake cleaner and wipe with clean shop towels. Inspect surfaces for any damage, warping, or cracks. Inspect intake manifold interior for carbon buildup or damage.
    ⚠Do not allow any debris to fall into intake ports on cylinder head
11. 11

    Install new intake manifold gasket
    Remove protective towels from cylinder head ports. Position the new intake manifold gasket on the cylinder head, ensuring all port openings align correctly and any locating pins engage properly. Gasket should lay flat without any folding or misalignment.
12. 12

    Install intake manifold
    Carefully lower the intake manifold onto the cylinder head, ensuring the gasket stays in position. Align all bolt holes and verify manifold seats flush against gasket. Insert all mounting bolts hand-tight to hold manifold in place. Reattach any ground wires or brackets removed earlier.
13. 13

    Torque intake manifold bolts
    Using a torque wrench, tighten the intake manifold bolts to 25 Nm (18 lb-ft) in the proper sequence: start from the center bolts and work outward in a crisscross pattern. Make multiple passes, first to 50% torque, then to final torque to ensure even gasket compression. Verify all bolts are at final torque.
    ⚠Uneven tightening or incorrect sequence can cause vacuum leaks or manifold warping
    Torque spec

    Intake Manifold Bolts25 Nm (18 lb-ft)
14. 14

    Reinstall support bracket and sensors
    Reinstall the intake manifold support bracket and torque mounting bolts to 45 Nm (33 lb-ft). Reconnect all electrical connectors to MAP sensor, purge valve, and any other sensors on the intake manifold. Ensure all connector locks click into place.
    Torque spec

    Mounting Bolts45 Nm (33 lb-ft)
15. 15

    Reinstall PCV system and vacuum lines
    Install new PCV valve o-ring if replacing. Install PCV valve into valve cover and twist clockwise to lock, then torque to 8 Nm (6 lb-ft) if accessible with torque wrench. Reconnect all vacuum lines to their original positions using reference photos. Reconnect brake booster vacuum line securely. Replace any damaged hose clamps.
    Torque spec

    PCV Valve8 Nm (6 lb-ft)
16. 16

    Reinstall fuel rail assembly
    Remove protective covers from injector ports. Lubricate new fuel injector o-rings lightly with clean engine oil if replacing. Carefully position fuel rail with injectors aligned to ports and press firmly into place. Install fuel rail bolts and torque in proper sequence to 12 Nm (9 lb-ft). Reconnect fuel line, ensuring it clicks and locks properly. Tug gently to verify connection.
    Torque spec

    Fuel Rail Bolts12 Nm (9 lb-ft)
17. 17

    Reinstall throttle body
    Install new throttle body gasket on intake manifold. Position throttle body and install mounting bolts, tightening in crisscross pattern to 10 Nm (7 lb-ft). Reconnect throttle body electrical connector. If coolant hoses were disconnected, reconnect them with new clamps and refill coolant system.
    Torque spec

    Throttle Body Bolts10 Nm (7 lb-ft)
18. 18

    Reinstall air intake system
    Reinstall air intake tube assembly, reconnect MAF sensor electrical connector, and secure air filter box with mounting bolts. Tighten clamp at turbo inlet securely. Ensure all connections are tight and no objects or tools remain in engine bay.
19. 19

    Final checks and battery reconnection
    Double-check all electrical connections, vacuum lines, and hoses are properly connected and secured. Verify no tools remain in engine bay. Reconnect negative battery terminal. Check coolant level and top off if necessary with Honda Type 2 (Blue) coolant.

Reassembly

1. All reassembly steps are included in the main procedure above
2. Torque specifications must be followed exactly to prevent vacuum leaks
3. Verify all electrical connectors are fully seated with locking tabs engaged
4. All vacuum lines must be routed exactly as original configuration

Verification

• Start engine and verify it idles smoothly without rough running or stalling
• Check for any vacuum leaks by listening for hissing sounds around intake manifold, throttle body, and vacuum line connections
• Monitor for fuel leaks around fuel rail and injectors while engine is running - shut down immediately if fuel leak is detected
• Verify no coolant leaks at throttle body connections if hoses were disconnected
• Use a scan tool to check for any diagnostic trouble codes (DTCs) related to intake system
• Test drive vehicle and verify normal throttle response, boost pressure, and acceleration with no hesitation or misfires
• After test drive, recheck all connections and look for any signs of leaks
• Recheck coolant level after engine reaches operating temperature and cools down

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