Engine Performance

NOTE: To provide best vehicle performance and lowest vehicle emissions, it is most important that the tune-up be done accurately. Use the specifications listed on the Vehicle Emission Control Information label found on the engine compartment hood.

1. Test battery specific gravity. Add water, if necessary. Clean and tighten battery connections.
2. Test cranking amperage draw.
3. Tighten the intake manifold bolts.
4. Perform cylinder compression test:

CAUTION: DO NOT overspeed the engine.

a. Check engine oil level and add oil, if necessary.
b. Drive the vehicle until engine reaches normal Operating temperature.
c. Select a route free from traffic and other forms of congestion, observe all traffic laws and briskly accelerate through the gears several times. The higher engine speed may help clean out valve seat deposits which can prevent accurate compression readings.
d. Remove all spark plugs from engine. As spark plugs are being removed, check electrodes for abnormal firing indicators (fouled, hot, oily, etc). Record cylinder number of spark plug for future reference.
e. Disconnect coil wire from distributor ant secure to good ground to prevent a spark from starting a fire.
f. Be sure throttle blades are fully open during the compression check.
g. Insert compression gage adaptor into the No. 1 spark plug hole. Crank engine until maximum pressure is reached on gauge. Record this pressure as No.1 cylinder pressure.
h. Repeat for all remaining cylinders.
i. Compression should not be less than 689 kPa(100 psi) and not vary more than 172 kPa (25 psi) from cylinder to cylinder.
j. If cylinder(s) have abnormally low compression pressures, repeat procedure.
k. If the same cylinder(s) repeat an abnormally low reading, it could indicate the existence of a problem in the cylinder.

NOTE: The recommended compression pressures are to be used only as a guide to diagnosing engine problems. An engine should NOT be disassembled to determine the cause of low compression unless some malfunction is present.

5. Clean or replace spark plugs as necessary. Adjust gap.
6. Test resistance of spark plug cables.
7. Inspect the primary wire. Test coil output voltage, primary and secondary resistance. Replace parts as necessary.
8. Perform a combustion analysis.
9. Test fuel pump for pressure.
10. Inspect air filter element.
11. Inspect crankcase ventilation system.
12. For emission controls refer to Powertrain Management.
13. Inspect and adjust accessory belt drives.
14. Road test vehicle as a final test.