1978 Models
- Check vacuum hoses for damage and proper routing. Start and warm engine to normal operating temperature. With engine idling, check that there are no leaks in EGR system feed line (exhaust manifold to EGR valve).
- Disconnect vacuum hose from EGR valve and temporarily connect vacuum hose from power brake booster to EGR valve. Engine should run rough or stall. If engine does not respond as indicated, check for a faulty EGR valve or clogged EGR passage.
- Connect a vacuum gauge to temperature valve, in place of vacuum hose that goes to EGR valve. With engine at normal operating temperature, there should be 2-4 in. Hg of vacuum. If not, replace temperature valve.