Re: Installed new carb insulator= slightly higher idle?
 

The last vacuum advance I had replaced was in my 74 Chevy C-10, but that was really easy once the cap & rotor were off. I wouldn't imagine it would be much different on your car. My recommendation is to have a roll of masking tape and a magic marker on hand to mark anything you disconnect so you are sure it goes back to its proper place.

Re: Installed new carb insulator= slightly higher idle?
 

Hang on a minute, I've never heard of a vacuum advance with two vacuum openings. Something isn't right.

Or do you mean that the carb has two vacuum ports?

You have to understand that most carbs have 2 vacuum ports on the front. One is exposed to manifold vacuum, and will always show vacuum (well while the engine is running).

The other port is called "ported" vacuum, and if you look inside the carb you'll notice that the vacuum port inside the carb is slightly above the butterflies - this is called "ported" vacuum because it only sees vacuum when the butterflies are open enough to expose the inside of that port to vacuum.

Your vacuum advance is supposed to be exposed to ported vacuum. I bet you put your vacuum advance on the manifold vacuum (which, by the way, will increase your timing at idle and therefore your idle speed)!

Go fix your vacuum lines and your problem should be fixed.

And if you have an automatic transmission, that will shift right again too.

-BC

Re: Installed new carb insulator= slightly higher idle?
 

This engine was designed by Honda to have manifold vacuum hoses connected to the vacuum advance.

There are actually two advance diaphragms in there. One works all the time and the other (I think it is the outer one) only supplies manifold vacuum when the engine coolant is below a certain temperature. This increases spark advance when the engine is cold. Vacuum is cut to this hose when the engine warms up enough.

Yes- you are right, that one diaphragm fails very often. Out of 6-7 distributors I tested at U-pull, only one was good. I priced the advance unit a few years ago and it was $50-60. If it is just the cold advance that is busted, then it would not be causing your wandering idle problem- but it would improve the way the engine runs during its warm up period in a few months when the weather gets cold.

If it is the main advance diaphragm that is busted, then you really should replace it.

Re: Installed new carb insulator= slightly higher idle?
 

I've been chasing this port all over the place! The problem is they make two different ones, one for the automatic and one for the Manual transmission. :(
I think I found one on line at Rock Auto.
I'll report back my findings as soon as I compare PN#'s to the factory Honda.

Re: Installed new carb insulator= slightly higher idle?
 

So far I struck out with the PN#. Rock Auto wants me to call back tomorrow and they will call the manufacture to see if it cross over.
Here's a link to the ones they offer for my Civic.

Re: Installed new carb insulator= slightly higher idle?
 

So, I guess you are crossing the P/N for Airtex/Wells?

Re: Installed new carb insulator= slightly higher idle?
 

Yes, the pn# Honda gave me doesn't Airtex/Wells.

Re: Installed new carb insulator= slightly higher idle?
 

Is this accurate for your car? I was trying to look on the Majestic Honda site for you.

https://www.hondaautomotiveparts.com/...b301_b0109.png

Re: Installed new carb insulator= slightly higher idle?
 

No, The Vacuum advance on mounted on the distributor, but has two ports like you have in the diagram.
Keep me posted if you find anything and thanks for the help! :thumbup:
Dean

Re: Installed new carb insulator= slightly higher idle?
 

Check out this site:

https://www.parts.am/Honda/findPart/6/110476

I've found the exact P/N on here, but you'll have to verify if the one's listed are more or less correct. It seems like the one for Airtex/Wells on RockAuto is for the A/T, not for your car being the M/T obviously.

Its linked to this submodel, w/ auto tranny:

https://www.parts.am/Honda/findPart/6/114955

Your P/N should be this one?

30104-PE1-830

It's the same P/N for all of the M/T, with only the Si having a different vacuum advance part.