Compression (Highlander)
WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 2003 Toyota Tundra, 2003 Toyota Tacoma, 2003 Toyota Sienna, 2003 Toyota Sequoia, and 2003 Toyota Land Cruiser. However, it is still accessible from the selected car via links, so may be relevant.
- Warm engine to normal operating temperature before checking compression. Stop engine. Ensure battery is fully charged. Disconnect injector connectors.
- Remove intake air surge tank.
- Disconnect accelerator cable. Remove bolt, and disconnect speed control cable with bracket. Disconnect throttle position sensor connector and Idle Air Control (IAC) valve connector
- Remove 3 bolts and disconnect power steering pressure tube from intake air surge tank, throttle body bracket and No. 1 engine hanger.
- Disconnect 2 water bypass hoses and No. 6 air hose. Disconnect purge hose. Disconnect hoses and cables.
- Remove 2 bolts and No. 1 engine hanger. Remove 2 bolts and throttle body bracket.
- Disconnect engine wire from emission control valve set. Using an 8 mm socket hexagon wrench, remove 2 bolts, 2 nuts and intake air surge tank. See Fig 1.
- Remove ignition coils. See IGNITION COIL under IGNITION SYSTEMS in REMOVAL & INSTALLATION - V6 & V8 article. Remove spark plugs.
- Fully open throttle. Using Compression Gauge (SST 09992-00500), check compression while cranking engine. Read compression in a short a time as possible. Ensure compression is within specification. See COMPRESSION SPECIFICATIONS table.
- If cylinder compression is low, pour a small amount of engine oil into cylinder through spark plug hole and inspect again. If adding oil increases compression, it is likely that piston rings and/or cylinder bore are worn or damaged. If pressure stays low, a valve may be sticking or seating improperly, or there may be leakage past head gasket.
- Install and tighten spark plugs to 13 ft. lbs. (18 N.m). Reinstall and tighten ignition coils to 71 INCH lbs. (8 N.m).