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CONDITION POSSIBLE CAUSES CORRECTION ENGINE STALLS 1. Carbon build-up on throttle plate 1. Remove throttle body and de-carbon. 2. Engine idle speed too low 2. Check Idle Air Control circuit. (Refer to 3. Worn or incorrectly gapped spark plugs 3. Replace or clean and re-gap spark plugs 4. Worn or burned distributor rotor 4. Install new distributor rotor 5. Spark plug cables defective or crossed 5. Check for correct firing order or replace 6. Faulty coil 6. Test and replace, if necessary (Refer to 7. Intake manifold vacuum leak 7. Inspect intake manifold gasket and 8. EGR valve leaking or stuck open 8. Test and replace, if necessary (Refer to ENGINE MISSES 1. Worn or incorrectly gapped spark plugs 1. Replace spark plugs or clean and set 2. Spark plug cables defective or crossed 2. Check Idle Air Control circuit. (Refer to 3. Dirt in fuel system 3. Clean fuel system 4. Burned, warped or pitted valves 4. Install new valves 5. Faulty coil 5. Test and replace as necessary (refer to SERVICE DIAGNOSIS—MECHANICAL ENGINE MECHANICAL DIAGNOSIS CHART CONDITION POSSIBLE CAUSES CORRECTION NOISY VALVES/ 1. High or low oil level in crankcase 1. Check for correct oil level. Adjust oil level 2. Thin or diluted oil 2. Change oil (Refer to Engine Oil Service 3. Low oil pressure 3. Check engine oil level. If ok, Perform oil 4. Dirt in tappets/lash adjusters 4. Clean/replace hydraulic tappets/lash 5. Bent push rod(s) 5. Install new push rods 6. Worn rocker arms 6. Inspect oil supply to rocker arms and 7. Worn tappets/lash adjusters 7. Install new hydraulic tappets/lash 9 - 10 4.0L ENGINE WJ DIAGNOSIS AND TESTING (Continued) |