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Volvo 1990 780 Model
pg. 97 Servicing
Torque manifold nuts
The manifold nuts should be torqued at the 600-1,200 mile (1000-2,000 km) inspection. A loose
manifold could alter air/fuel ratio and cause an increase in emissions and/or poor driveability.
Valves
The valve clearance should be check and, if necessary, adjusted every 30,000 miles (48,000 km).
Air cleaner
Replace the air cleaner cartridge with a new one every 30,000 miles (48,000 km). The cartridge should
be replaced more often when driving under dirty and dusty conditions, The filter cannot be cleaned and,
therefore, should always be replaced with a new one.
Vacuum fittings, hoses and connections
Unstable idle, misfiring, or poor emission control is often caused by leaking vacuum hoses or
connections. Check hoses and connections on distributor vacuum unit, connections on heater control
servo systems and hydraulic brake servo.
Checking and adjusting idle air control system
Your Volvo is equipped with an electronically-controlled idle air control system that requires no
checking or adjustment.
Fuel system cap, tank and lines, and connections
The effectiveness of the fuel system to contain hydrocarbons is dependent largely on a leakfree system.
file:///K|/ownersdocs/1990/1990_780/90780_21.htm (1 of 7)12/30/2006 8:28:05 AM
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