Jeep 1987 Wrangler Workshop Manual page 250

HI
ENGINES
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HI
GENERAL SERVICE AND DIAGNOSIS
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Service Diagnosis - Performance (Continued)
Condition
Possible Cause
Correction
P O W E R N O T U P
T O N O R M A L
(Continued)
(6) Incorrect valve timing.
(7) Faulty ignition coil.
(6) Check valve timing and repair as
necessary.
(7) Test coil and replace as necessary.
(8) Faulty ignition wires. (8) Test wires and replace as necessary.
(9) Improperly seated valves. (9) Test cylinder compression and repair as
necessary.
(10) Blown cylinder head gasket. (10) Replace gasket.
(11) Leaking piston rings. (11) Test compression and repair as necessary.
(12) Worn distributor shaft. (12) Replace shaft.
(13) Improper feedback system operation. (13) Refer to Feedback System Diagnosis.
I N T A K E
B A C K F I R E
(1) Improper ignition timing.
(2) Faulty accelerator pump discharge.
(1) Adjust timing.
(2) Repair as necessary.
(3) Defective E G R C T O valve. (3) Replace E G R C T O valve.
(4) Defective T A C vacuum motor or
valve.
(4) Repair as necessary.
(5) Lean air/fuel mixture.
(5) Check float level or manifold vacuum for
air leak. Remove sediment from bowl.
E X H A U S T
B A C K F I R E
(1) Air leak into manifold vacuum.
(1) Check manifold vacuum and repair as
necessary.
(2) Faulty air injection diverter valve. (2) Test diverter valve and replace as
necessary.
(3) Exhaust leak.
(3) Locate and eliminate leak.
P I N G O R S P A R K
K N O C K
(1) Incorrect ignition timing.
(2) Distributor centrifugal or vacuum
advance malfunction.
(1) Adjust timing.
(2) Inspect advance mechanism and repair as
necessary.
(3) Excessive combustion chamber
deposits.
(3) Remove with combustion chamber cleaner.
(4) Air leak into manifold vacuum
(4) Check manifold vacuum and repair as
necessary.
(5) Excessively high compression
(5) Test compression and repair as necessary.
(6) Fuel octane rating excessively low.
(6) Try alternate fuel source.
80652E
B-16