Help ...Need Carb, Intake Specialist!!

[Adrian Mosforth]

OK...I have tried asking before about my 65 Caddy really rough idle problems, but I think I wasnt explaining properly...

Here goes!

Got the car about 5 years ago...It has a Rochester 4GC carb...No metal shim needed!!!

Car had a rough idle, so I plugged all vacuum lines, and checked timing, new points, rotor, cap, plugs, wires...Nothing...

So I bought a Neihoff "1 size fits all Rochester 4GC" gasket set.  They suck!!

I think the carb might have been rebilt before, but i dunno.  None of the Carb Bowl to Throttle body gaskets really worked  that well.  Either the bores were too large on the gaskets or they had the wrong "fit", meaning the pins on the carb bowl to hold the gasket were to close together

Anyways, I used a gasket that had so-called "Vapour Vent Passages" on the primary side...It was the best fit, and looked similar to the one I removed...They all had them for the secondaries, but for the primary side???  It will allow air into the carb, but I guessed it was designed for that.

So I still have a very rough, with bad misfiring at idle when it is cold...Not that bad when it has warmed up!

Then I noticed that the "Choke Heat Tube" was broken.  Like really broken!!!  Half of it came out the other half stayed in!  So I used some Thermal Bond to reattach it and make sure that it stayed put...Might have sealed the Choke heat tube passage shut...I dunno.

Tried adjusting the idle mixture, timing, almost anything I can think of.  Yet I still have a Very rough, misfiring cold idle, not as bad when it warms up!

Does anyone have any ideas???  Please dont say check for vacuum leaks because all of the hoses are disconected right now and the ports plugged!  However, when I spray water at the front base of the carb, the engine does slow down...You guessed it, that is where the Bowl to Throttlebody gasket is!!!

The only thing I can think off are
1.) The "Vapour Vent Passages" in the gasket,
or
2.) Somehow I am getting Air from the Choke Heat Tube.

Questions are...Would a broken Choke heat Tube allow air into the manifold or carb???

Does anyone have a pic of the proper bowl to throttlebody gasket, or maybe any advice as towhat the gasket should look like?

If needed, I can email a picture of the 2 different gaskets that came in the kit...The ones with the "Vapour Vent Passages" and the one without them.

Could it be the Choke Heat Tube???  My mechanic wants to put an electric choke on it (Thinking that MAY help) but I would like to try and keep my baby original.  She only has 57000 on her...

Could it be that I should just sell that car because I am tired of the headaches?  Joking!!!

Please, Please, Please help!!!

[Bruce Reynolds # 18992]

Gday Adrian,

Okay, lets start with the obvious first.

You say that it runs really rough till it warms up.

(1)  Now, That would indicate to me that you either have a Lean problem caused by the choke not operating......If you operate the choke by hand, does the idling smooth out, even though the revs are up a fair bit, like 1000 or higher?.....If so, then the mixture at idle when cold is too lean.....The choke is there to richen it up whilst cold.

(2)  Is there a vacuum leak that is only leaking whilst cold?......Is there a vacuum fitting that isnt working correctly?

Just a few to start with.

Bruce.

[Adrian Mosforth]

Gday Adrian,

Okay, lets start with the obvious first.

You say that it runs really rough till it warms up.

(1)  Now, That would indicate to me that you either have a Lean problem caused by the choke not operating......If you operate the choke by hand, does the idling smooth out, even though the revs are up a fair bit, like 1000 or higher?.....If so, then the mixture at idle when cold is too lean.....The choke is there to richen it up whilst cold.

(2)  Is there a vacuum leak that is only leaking whilst cold?......Is there a vacuum fitting that isnt working correctly?

Just a few to start with.

Bruce.


Hi Bruce.....OK....The Choke does work!  Amazing isnt it!!!  But it does close and it goes to fast idle...

I noticed as well that it stumbles when I am pulling away from a stop light.

Does that help any???

As for the vacuum leak when cold...That is what I was thinking, but I cant seem to find any....

Oh well...I am going tot get a rebuilt carb anyways now...I am fed up of it running like crap!

[Rhino 21150]

Have you checked the intake manifold gasket? Try a rebuild kit from NAPA, they have never given me trouble, even for the Fiats! And if the carb is off the car, take it with you.

[Denise 20352]

  Hook it up to a CO and HC tester.  It will tell you just about anything you need to know about your rough idle.

-denise