Jeep Cherokee 1999 Electronic Service Manual page 1029

9 - 12 ENGINE
DI AGN OSI S AN D T EST I N G (Cont inue d)
CONDITION
ENGINE STALLS OR ROUGH
IDLE
ENGINE MISSES ON
ACCELERATION
POSSIBLE CAUSES
1. Carbon build-up on throttle plate
2. Engine idle speed too low
3. Worn or incorrectly gapped spark
plugs
4. Worn or burned distributor rotor
5. Spark plug cables defective or
crossed
6. Faulty coil
7. Intake manifold vacuum leak
8. EGR valve leaking or stuck open
1. Worn or incorrectly gapped spark
plugs
2. Spark plug cables defective or
crossed
3. Dirt in fuel system
4. Burned, warped or pitted valves
5. Faulty coil
CORRECTION
1. Remove throttle body and
de-carbon. (Refer to Group 14 for
correct procedures)
2. Check Idle Air Control circuit.
(Refer to Group 14, Fuel System)
3. Replace or clean and re-gap spark
plugs (Refer to group 8D, Ignition
System)
4. Install new distributor rotor
5. Check for correct firing order or
replace spark plug cables. (Refer to
Group 8D, Ignition System for correct
procedures.)
6. Test and replace, if necessary
(Refer to group 8D, Ignition System)
7. Inspect intake manifold gasket and
vacuum hoses. Replace if necessary
(Refer to Group 11, Exhaust System &
Intake Manifold)
8. Test and replace, if necessary
(Refer to group 25, Emission Control
Systems)
1. Replace spark plugs or clean and
set gap. (Refer to group 8D, Ignition
System)
2. Check Idle Air Control circuit.
(Refer to Group 14, Fuel System)
3. Clean fuel system
4. Install new valves
5. Test and replace as necessary
(refer to group 8D, Ignition System)
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