Idle problem on my 1959

[Brodie]

I am hoping someone will help me figure out what is wrong with the idle on my 1959 Cadillac.  When I first start the car and put it in reverse, the car wants to stall.  Once I start driving, every time I have to stop at a stop sign, the car starts to rumble and grumble and almost sounds like it wants to stall.  When the car comes to a full stop, the idle picks up again and sounds ok (but sometimes idles very rough at a stop).  After I drive the car for a while and everything is warmed up, the car idles down a lot better when I come to a stop.

Is this just a case of the car needing to warm up, or does the carburator need to be adjusted?  Does the tv rod need adjustment?  Any suggestions would be appreciated.  I want to try and fix the problem myself.  I do not have any special equipment, so I am hoping a solution to the problem would not require any (this is probably wishful thinking).

Thanks,
Brodie

[Bruce Reynolds # 18992]

Brodie,

How long has the engine been like this, or has it suddenly developed the problem?

It is quite possible that you have a vacuum leak so check out all the vacuum lines.

To do a proper tune-up, you will have to adjust the base idle to at least 550 rpm, when hot, and with the choke on, it will be higher than that.   You will also need to adjust the timing to factory specs.

If the choke is working correctly, you should be able to drive away with minimal warm-up time.

Bruce,
The Tassie Devil(le),
60 CDV

[Brodie]

Thanks for your reply Bruce.  The problem has been there for quite a long time, ever since a friend screwed up the timing and idle when he tried to tune it up.  I took it to a garage where they fixed the timing and idle, but it never seemed quite right since then.  

This may sound like a dumb question, but how do you check the vacuum hoses?  What am I looking for and how do I fix it if there is a leak?

Thanks,
Brodie

[Porter 21919]

Brodie,

Cap off each hose one at a time at the source and see if the engine smooths out.


Porter

[Ivan Zanatta]

I had a similar problem on my 60 (4 barrel Rochester carby), and it turned out that someone had tuned up my mixture incorrectly. With a CO/CO2 analyser it was corrected in 2 minutes. Carby places usually have these exhaust analysers.
If youre chasing vaccuum leaks, isolate all the vac. driven devices at their source, E.G. the manifold or carby end. If these points are blocked up This will at least tell you that if its still rough, its on the motor somewhere (inlet manifold, carby base gasket, etc.) If you suspect a vac. leak, squirt a little engine oil at the point while engine is running, see if it dissapears.

[George]

attached to the firewall just behind the distributor, you will see a valve. It looks like a vaccuum  advance. its purpose is to stop the accelerator from suddenly closing. ie, when you remove your foot from the gas pedal and apply brakes, instead of just closing the throttle plate suddenly, it resists closure and delays the operation of the linkage. If this ceases to work the carb mechanism closes with a jolt this can cause the symptoms you describe especially when the engine is cold. Check it works.