vacuum advance

[stephanspider2000]

hello,
since my spider is still idling a little high (about 1000 rpm)
i was looking at things under the hood and i found out my vacuum advance was not working
so could that be the problem for the high idling??(haven't tried it yet)
is the vacuum advance just for good mileage or does it affect performance to.

[So Cal Mark]

the only way that a vacuum advance could cause your problem would be if it was stuck in full advance mode

[stephanspider2000]

ok , but it is a vacuum leak isn't it?
the pin on the vac.advance isn't pulled in so i'm assuming it's not in full advance mode

when i cap it off is that harmfull for the engine, my parts supplier doesn't have a vac. advance in stock so it can take a while
i read previous topics on this , and i conclude that no vac.advance doesn't affect performance, am i right?

[rlux4]

I have run without a vacuum advance for over a year. Because there is no spare vacuum to supply the vacuum advance under acceleration, I have never noticed it affecting quickness. I get 24-26 mpg, so it isn't affecting me there enough to worry about either. I had bought a new replacement not long after I got my car, and the new module only lasted a couple of months before the diaphragm blew, and I never noticed the difference, so I just leave it capped off. I have capped the vacuum line to keep from having the vacuum leak, and I capped the nipple on the module. (Probably doesn't need it, I just did it to ease my mind.)
My numbers were slightly higher when I had it smogged, so it could be affecting emissions, I'm not knowledgeable enough in that area to say.
Ron

[ga.spyder]

I agrre with Ron.The vac advance isnt causing a high idle.I also replaced my vac. adv. and felt no difference at all. I keep my idle set at 1000 rpm,thats where it is the smoothest.That really isnt that high.If your timing is right,it is very easy to adjust the idle on the f.i.
Craig

[majicwrench]

The vacuum advance should certainly affect mileage and off-idle smoothness and light throttle power. It will not affect full throttle power. The engine was designed by some very smart engineers to run it's best WITH the vacuum advance. In the long run, you are not burning the fuel as completely without the advance, and more of it could be ending up on the cylinder walls and in the crankcase.
Yes, if the diaphram is bad it is creating a very tiny vacuum leak which may in theory increase your idle by a very small amount, IF there is any vacuum present on the line at idle. BUt no, it is not causing your fast idle.
Get a new advance!!

[TJC]

Whether we talking a carb or FI, the ignition's vacuum advance takes it's signal from the "ported" vacuum line which is just ABOVE the throttle plate. Which means there should be no vacuum in that line at idle. Therefore, even if you cut the line wide open, it should not affect your idle condition. In fact, you should disconnect the vac advance line when setting idle speed to ensure it is set without any inadvertent ignition advance.

[stephanspider2000]

well i drove the car today with no vacuum advance, and the hose capped of
It did not affect my idle speed and i did not noticed any difference in performance
but i don't think Fiat put it in just for fun
so i ordered a new vacuum advance today, it should come in about two weeks
untill then i'm driving without one

[TJC]

well i drove the car today with no vacuum advance, and the hose capped of
It did not affect my idle speed and i did not noticed any difference in performance
but i don't think Fiat put it in just for fun
so i ordered a new vacuum advance today, it should come in about two weeks
untill then i'm driving without one

Vacuum advance is not for performance, it's for fuel economy. The vacuum signal is only active at part throttle, advancing the ignition for efficiency only at low loads where there's no danger of knocking, i.e., affecting mostly highway fuel economy.