Suburban 3/4 Ton 4WD V8-305 5.0L (1986)
4.
Run engine at 1000 RPM and record vacuum reading.
5.
Slowly increase engine speed to 2500 RPM and record vacuum reading at a steady 2500 RPM.
6.
If vacuum reading at 2500 RPM decreases more than 3 inches Hg from reading at 1000 RPM, check for exhaust restrictions as outlined for models
with air injection.
7.
If no restrictions are found, repeat check with exhaust pipe(s) disconnected from manifold(s).
8.
If vacuum readings still differ by more than 3 inches Hg, check valve timing. On models without air injection or EGR, connect suitable
vacuum gauge to intake manifold vacuum, and observe gauge with engine idling at normal operating temperature. If gauge reading
regularly drops to zero, check exhaust system for restrictions and repair as needed.
