Volvo 740 GL - Manual (Page 84)

1985 Volvo 740 GL, GLE, Turbo
Rest pressure incorrect
Test rest pressure and the fuel system for leaks.*
If no fault is found following the steps above, contact
your Volvo dealer
* Should be checked by a Volvo dealer.
pg. 75 Service diagnosis
Condition: Erratic idle (misfiring)
Possible cause Correction
Intake system leaking.
Check vacuum hose connections at manifold and
auxiliary air valve.
Spark plugs, high tension leads or distributor cap
worn (defective) Clean distributor cap and leads, check the cap for
cracks. Replace defective or worn parts.
Worn spark plugs. Remove. Clean or replace spark plugs.
Uneven compression. Test compression.*
Condition: Engine stalls at irregular intervals
Possible cause Correction
Defective wires.
Check wire terminals at: fuel pump, fuse No. 1 and 11, coil, distributor, ignition
switch and relays.
Intake system leaking. Check vacuum hose connections at manifold and auxiliary air valve.
Fuel filter clogged. Clean fuel tank filter and replace line fuel filter.
Condition: Misfiring at highway driving speed
Possible cause Correction
Spark plugs
fouled.
Drive the vehicle in a lower gear and keep the engine rpm higher for a few miles in
order to remove carbon deposit on the spark plugs. If this procedure is not
effective, clean or replace the spark plug.
Please be aware that misfiring spark plugs can cause damage to the catalytic
converter.
* Should be checked by a Volvo dealer.
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