Hot Engine Test

HOT ENGINE TEST





1. Disconnect the vacuum hose from the EGR valve and connect a vacuum pump/gauge to the hose.
2. Start the engine and wait for the cooling fan to come on.
3. Remove the control box from the firewall by removing the two bolts, then remove the control box cover by removing the four screws.
Vacuum should be as follows:

Condition / Vacuum at EGR Hose
(1) Idle / No
(2) 3,000 rpm / Yes, 2 - 6 in. Hg
(3) 3,000 rpm with blocked vacuum bleed * / Less than 2 in. Hg
(4) Rapid acceleration / Yes, 2 - 6 in. Hg
(5) Deceleration / No

* See image for vacuum bleed

Setup For Test Condition 3:

- If vacuum is available at idle (condition 1) check the vacuum hoses for proper routing and connections, then check for correct idle speed and idle mixture, and make adjustment as necessary.
- If there is no vacuum in conditions 2 and 4, check the thermovalve A.
Disconnect the #18 vacuum hose from the thermovalve A. Check for vacuum at the #18 hose.
- If there is no vacuum, check the routing for the #18 vacuum hose and repair or replace as necessary.
- If there is vacuum, replace the thermovalve A and retest.
- If vacuum is more than 2" Hg in condition 3, replace the EGR control valve and check the vacuum hoses for proper routing and connections.