Compression (4Runner 4.0L V6)
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- Warm engine to normal operating temperature before checking compression. Stop engine. Ensure battery is fully charged.
- Remove V-bank cover and air cleaner assembly.
- Remove intake air surge tank.
- Disconnect 2 water bypass hoses, fuel vapor feed hose and ventilation hose.
- Disconnect 2 vacuum switching valve (VSV) connectors and throttle body w/motor connector. See Fig 1.
- Separate 3 wire harness clamps and hose clamp. Remove 2 bolts and throttle body bracket.
- Remove bolt and oil baffle plate. Remove 4 bolts and 2 surge tank stays. Remove 2 nuts. Using a 8 mm socket hexagon wrench, remove 4 bolts, intake air surge tank and gasket.
- Remove ignition coils. See IGNITION COIL under IGNITION SYSTEMS in REMOVAL & INSTALLATION - V6 & V8 article. Remove spark plugs. Disconnect injector connectors.
- Fully open throttle and using compression gauge, 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.
- Connect injector connectors. Install and tighten spark plugs to 13 ft. lbs. (18 N.m). Reinstall and tighten ignition coils to 66 INCH lbs. (7.5 N.m).
- Install and tighten intake air surge tank bolts and nuts to 21 ft. lbs. (28 N.m). Install and tighten surge tank stay bolts to 15 ft. lbs. (21 N.m). Install and tighten oil baffle plate bolt to 80 INCH lbs. (9 N.m). Install and tighten throttle body bracket bolts to 16 ft. lbs. (21 N.m). Install air cleaner assembly and V-bank cover.