Engine Controls - Adjustments Isuzu Impulse II

ENGINE MECHANICAL

Before performing any on-vehicle adjustments to fuel or ignition systems, ensure engine mechanical condition is okay.

Stylus (1.6L SOHC)

1. Valves should be adjusted every 15,000 miles. With engine cold, remove rocker cover. Check torque of rocker arm shaft bracket nuts. Tighten rocker arm shaft bracket nuts to 16 ft. lbs. (22. N.m).
2. Position No. 1 piston at TDC of compression stroke. Check valve clearance between rocker arm and valve stem. See VALVE ADJUSTMENT SEQUENCE (1.6L SOHC) and VALVE CLEARANCE ADJUSTMENT (1.6L SOHC) tables. VALVE ADJUSTMENT SEQUENCE (1.6L SOHC) Piston No. on TDC. Adjust Intake Valves No. Adjust Exhaust Valves No. 1 1 & 2 1 & 3 4 3 & 4 2 & 4
3. To adjust remaining valves, turn crankshaft 360 degrees (one full turn) until No. 4 piston is at TDC of compression stroke. Check valve clearance. See VALVE CLEARANCE ADJUSTMENT (1.6L SOHC) table. Replace rocker cover gasket (if necessary) and reinstall rocker cover.

VALVE CLEARANCE ADJUSTMENT (1.6L SOHC)

Impulse & Stylus (1.6L DOHC)

Scheme 1

1. Disconnect negative battery cable. Remove rocker cover. Remove spark plugs. Rotate engine until "0" degree mark on timing belt cover aligns with crankshaft pulley timing mark groove.
2. Ensure cylinder No. 1 is at TDC of compression stroke by removing distributor cap. Rotor should point at No. 1 spark plug wire terminal. If rotor is not pointing as indicated, rotate crankshaft one revolution (360 degrees) and realign timing marks.
3. Measure and record intake valve clearance of cylinders No. 1 and 2, and exhaust valve clearance of cylinders No. 1 and 3. Rotate crankshaft one complete revolution (360 degrees), realigning timing marks. Measure and record intake valve clearance of cylinders No. 3 and 4, and exhaust valve clearance of cylinders No. 2 and 4. NOTE: Both camshaft rear bearing caps must be removed to access adjusting shim in tappet recess.
4. To adjust valve clearance and replace adjusting shim, turn camshaft lobe downward on valve to be adjusted. Insert Valve Lash Spring Spacer (J-38413-2 left or J-38413-3 right) between camshaft journal and camshaft lobe next to shim. (Scheme 1) Turn camshaft lobe upward. Using a screwdriver and magnet, remove adjusting shim from tappet recess.
5. Calculate shim thickness using shim thickness selection charts. (Scheme 2)and (Scheme 3). The following formula will also calculate shim thickness: N=T+A N = Thickness of shim required. T = Thickness of shim removed. A = Valve clearance measured minus valve clearance specification.
6. Replace removed adjusting shim with another shim that will allow the required valve clearance. See VALVE CLEARANCE ADJUSTMENT (1.6L DOHC) table. Repeat procedure as required.

VALVE CLEARANCE ADJUSTMENT (1.6L DOHC)

Scheme 2

Scheme 3

Scheme 4

1. With transmission in Neutral or Park, start engine and warm to normal operating temperature. Ensure CHECK ENGINE light is off. Turn engine and all accessories off.
2. Connect jumper wire between ALDL diagnostic connector terminals No. 1 and 3. ALDL connector is White 3-pin connector, located behind right side of instrument panel. (Scheme 4) Connect timing light to No. 1 spark plug wire. Start engine.
3. Check ignition timing. See IGNITION TIMING specification table. Increase engine speed to 1500-2000 RPM to read timing (if necessary).
4. Adjust timing by loosening distributor hold-down bolt and turning distributor. Tighten distributor hold-down bolt to 17 ft. lbs. (24 N.m). Recheck timing. Remove jumper wire from ALDL connector and ensure CHECK ENGINE light is off. Idle speed is automatically controlled by ECM.

IGNITION TIMING (Degrees BTDC@RPM)

IDLE SPEED

Idle speed is controlled by Idle Air Control Valve and is not adjustable. Throttle stop screw is preset at factory and sealed in position.

IDLE SPEED SPECIFICATIONS

THROTTLE POSITION SENSOR (TPS)

TPS is an auto-zeroing type and is not adjustable. If Code 21 is indicated, see appropriate G - TESTS W/ CODES article in the ENGINE PERFORMANCE Section.