Sable V6-183 3.0L VIN U FI (1998)
10. LATE VALVE TIMING: A steady but low reading could be caused by late valve timing.
11. IGNITION TIMING RETARDING: Retarded ignition timing will produce a steady but somewhat low reading.
12. INSUFFICIENT SPARK PLUG GAP: When plugs are gapped too close, a regular, small pulsation of the needle can occur.
13. INTAKE LEAK: A low, steady reading which can be caused by an intake manifold or throttle body mounting flange gasket leak.
14. BLOWN HEAD GASKET: A regular drop of fair magnitude can be caused by a blown head gasket or warped head-to-block surface.
15. RESTRICTED EXHAUST SYSTEM: When the engine is first started and is idling, the reading may be normal but as the engine rpm is
increased, the back pressure caused by a clogged muffler, kinked tail pipe or other concerns, will cause the needle to slowly drop to zero. The
needle then may slowly rise. Excessive exhaust clogging will cause the needle to drop to a low point even if the engine is only idling.
When vacuum leaks are indicated, pinpoint and correct the cause. Excess air leaking into the system will upset the fuel mixture and cause concerns
such as rough idle, missing on acceleration or burned valves. If the leak exists in the power brake, the system will not function correctly.
ALWAYS FIX VACUUM LEAKS.
