Yugo Workshop Manuals
Yugo L4-1300cc 1.3L (1991)
Transmission and Drivetrain > Automatic Transmission/Transaxle > Component Information > Technical Service Bulletins > Technical Service Bulletins for Automatic Transmission/Transaxle: > ATRATB028 > Oct > 90 > A/T - Engine Vacuum Testing > Page 760
With the engine idling, continued fluctuation of 1 to 2 inches may indicate an ignition problem. Check the spark plugs, spark plug gap, primary ignition
INTAKE SYSTEM LEAKAGE, VALVE TIMING, OR LOW COMPRESSION
A vacuum reading at idle much lower than normal can indicate leakage through intake manifold gaskets, manifold-to-carburetor gaskets, vacuum brakes
EXHAUST BACK PRESSURE
Starting with the engine at idle, slowly increase engine speed to 3000 RPM, engine vacuum should be equal to or higher than idle vacuum at 3000 RPM.
If vacuum decreases at higher engine RPM's, an excessive exhaust back pressure is probably present.
CYLINDER HEAD GASKET LEAKAGE
With the engine Idling, the vacuum gauge pointer will drop sharply, every time the leak occurs. The drop will be from the steady reading shown by the
FUEL CONTROL SYSTEM TROUBLES
All other systems in an engine must be functioning properly before you check the fuel control system as a cause for poor engine performance. If the
Engine problems can affect transmission performance.
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