Test NTC-4: Checking Engine Mechanical Systems

At this point in diagnostic test procedure, all engine electrical control systems have been determined to be operating as designed and not causing a driveability problem. Following additional items should be checked as possible causes:

• Check engine vacuum. Engine vacuum must be at least 13 in. Hg with transmission in Neutral.
• Check engine valve timing.
• Check engine compression.
• Check camshaft lobes for abnormal wear.
• Check crankshaft sensor slots for debris or deterioration.
• Check exhaust system for restrictions.
• Ensure PCV system is functioning properly.
• Check for defective camshaft and crankshaft sprockets.
• Check improper torque converter stall speed.
• Check power brake booster for internal vacuum leak.
• Check fuel for contamination.
• Ensure proper injector driver wiring is installed on correct injector. Ensure injector is not plugged or restricted.
• Check for related Technical Service Bulletins (TSBs) that may apply to the problem.