1984 300TD,auto, black vacuum line that goes thru firewall to under dash area is disconnected, I have panel out & have unsuccessfully spent time looking for open hose that it connects to, I have looked at forum diagrams but color one I found does not show black line, engine shut down is delayed, tranny shifts sloppy, so I started looking for leak & found loose black plastic line under dash

Black plastic line under dash is a vent line.............it's not connected to anthing on the dash end.

I assumed it had disconnected as the other end comes off the T that comes off the IP, any advice to find vacuum leak? I also have lost my tach, can you tell me where that gets it's signal?

That "T" is the vent line. It provides vent air for the vacuum control valve and the EGR valve.

Why do you believe you have a vacuum leak? What are the symptoms?

I have a delayed shut down & sloppy trans. shifts, the delayed shut down is a recent development, tranny has always shifted rough

If you have a vacuum leak, the likely culprits are the EGR system (the black box on the top of the valve cover) or the climate control system.......multiple pods that develop leaks.

You'll need a Mityvac and an understanding of the system to track these down.

The vacuum valve that shuts off you Fuel Injection pump as attatched down at the bottom of the ignition switch and by the steering wheel lock. This is a possible source of the problem. It cost aroud $27 (internet price) to replace it. I will PM you some info. as to where to find the switch on your car.

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84 300D, 82 Volvo 244Gl Diesel