-72 Deville don't run good at low speed / low rpm!

[Soren Johnson]

It runs great when I start it in the morning and go for a ride.
So I can drive about 20 km, park it, let it stay for an hour.
Then when I start it again it don't start so easy and runs very poorly at low speed.
Sometimes it runs so bad that it stops when i put the gear in drive.
But att higher speed, 50-60-70 miles/hour I have no problem.
Only problem when hot and with low rpm and low speed.
What can this bee?

[TJ Hopland]

Check the usual stuff like vacuum hoses and other vacuum leaks.  I would also look at the springs and weights in the distributor to make sure they are moving freely as they should.  Check to make sure the vacuum advance is working.  I believe by 72 they were using the thermal vacuum switch that is located just under the distributor in the block.  Its supposed to switch the distributor vacuum between ported and manifold vacuum depending on coolant temp. Maybe the switch is bad or leaking or one of the lines is off so it leaks only when its warmed up but works properly in the cold mode.

Dont rule out a bad tank of gas, it seems to happen more and more these days with all the crap they add.

[Soren Johnson]

It was the "Thermal Vacuum Switch".
The vacuum lines where connected wrong.

[TJ Hopland]

Its nice when things are a simple easy and cheap fix!