1977 2.7 911 vacuum advance question

[ampex351]

I am still having trouble getting the CIS adjusted properly but on the other hand I just found that the hose to the vacuum advance on the distributor is connected but there is a rubber plug somebody put in it. I took the plug out of the line and pushed it back on to the vacuum advance and it makes no difference. I just bought the car 3 months ago. It was running absolutely great until the weather turned cold at which time I set about adjusting the fuel mixture with the 3mm wrench. The aux air reg. had also seized up so I sprayed WD40 into it, reinstalled the hose and went about adjusting the fuel. I've gone richer and leaner both but it still cuts out when I get on it. I know...I'm trying to explain 2 different things here. Just don't know what to do next. It was running stellar just before the cold set in and the AAR seized up.

Thanks

[Walter_Middie]

Ampex,

The vacuum line will slightly change the timing at idle, but you may not notice it.


The mixture screw is very sensitive - you don't have to move it much. How far have you turned this screw?

Do you have fuel pressure gauges? If not, they are a good investment and will be necessary to diagnose poor running.

[rwest]

The ‘77 distributors are vacuum retard. I don’t notice a difference with it hooked up or blocked. Mine had a red cover/ plug fitting on the port that the hose hooked up to blocking vacuum when I bought it. Ran it that way for twenty years until I noticed it and removed.

Like I said, no difference in my experience.

[rwest]

The AAR will put a “ton” of unmetered air into the system if it isn’t closing once the engine warms up. You could try to block and cap the hose and valve once the car warms up and see if it isn’t closing.

[30westrob]

Since your running issues started with cooler weather, I would get a CIS gauge set and check, warm up regulator pressures. With time the regulators become too lean. Many posts on this issue. Rob

[boyt911sc]

Originally Posted by rwest

The AAR will put a “ton” of unmetered air into the system if it isn’t closing once the engine warms up. You could try to block and cap the hose and valve once the car warms up and see if it isn’t closing.

RWest,

The air passing through AAR is all metered unless you have a hole or crack on the vacuum line.

Tony

[rwest]

Originally Posted by boyt911sc

RWest,

The air passing through AAR is all metered unless you have a hole or crack on the vacuum line.

Tony

Yes, you’re correct, my error.

It does get the air off the boot after the fuel distributor, so metered; not sure where my brain was earlier.

[Bill Verburg]

Originally Posted by ampex351

I am still having trouble getting the CIS adjusted properly but on the other hand I just found that the hose to the vacuum advance on the distributor is connected but there is a rubber plug somebody put in it. I took the plug out of the line and pushed it back on to the vacuum advance and it makes no difference. I just bought the car 3 months ago. It was running absolutely great until the weather turned cold at which time I set about adjusting the fuel mixture with the 3mm wrench. The aux air reg. had also seized up so I sprayed WD40 into it, reinstalled the hose and went about adjusting the fuel. I've gone richer and leaner both but it still cuts out when I get on it. I know...I'm trying to explain 2 different things here. Just don't know what to do next. It was running stellar just before the cold set in and the AAR seized up.

Thanks

'77 was the first year for the Warm up regulator thermo valve, make sure that this is working right first

[T77911S]

thermo valve and vacuum line form WUR to throttle body.
make sure the is vacuum at the WUR at IDLE. if not, it will not accelerate very if at all.
you can bypass the TTV, but it is very nice to have in very a vary cold climate.

for the dist.

find a vac hose with vac on it at idle. connect it to each of the ports to determine which one is advance and which is retard.
vac retard has vac ONLY at idle.
vac advance ONLY has vac above idle.
you can look at the TB and see which ports are above and below the plate, when closed.

[Flat6pac]

A 77 only uses vacuum retard to meet idle emissions. There is no advance connection until 1978 which was the first advance
Bruce