[2000CAYukon]

Engine off, using a vacuum pump, apply 18 Hg of vacuum. Start the engine, the vacuum should be zero and the EGR valve should have closed. Replace if it does not hold or drop to zero when engine is started? Also replace it is does not close when started.

TBI side of the solenoid should hold vacuum (engine off), replace if it does not.

Other things to check for poor performance when warm:

- clogged cat or exhaust
- fuel pump or relay (check fuel pressure)
- heat riser valve in air cleaner (should close when engine is hot so only cold air enters TBI)
- bad ignition coil
- timing chain

//2000CAYukon