High Idle issue when car is driven and set in Park...

[Fiat88]

I have a '79 which is an automatic, with a DFEV carb. The issue I have is that when the car is started cold, it idles ruffly and at below 800 RPMs and wants to cut out and if I pressed the accel. pedal it sometimes makes slight grinding sound and dies. Only until the car gets warmed up and reaches 190 on the temp guage. it will rev higher in on the tach gauge when press the accel. pedal and start to get smoother. Then when I go in reverse to backout my garage it idles at about 900 smoothly when put in park.. The car runs great after that, only that when I get to my destination and put the gear in Park it idles high at 1500 rpm.

I've first started experiencing these issues when the weather started getting colder and I had an oil cap and valve cover leak which was fouling my spark plugs. Last week I finally relaced the gaskets for the valve covers and a new oil cap. Last time I check it seems to have fixed the leak. So, could it just be the plugs need replacing, I checked and cleaned them. Any thoughts? Thanks.

-John

[So Cal Mark]

spark plugs won't cause your idle situation. It all sounds like carb issues, but vacuum leaks could confuse the situation too. Best to make sure all of the tune-up basics are right first

[Fiat88]

Mark,
I'm wondering about the left over colored vacuum hoses which have no place to go on the Weber 32/36 DFEV
I put in. Should I cap those lines or just leave them, could that be causing leaks? Thanks.

[So Cal Mark]

all of those thermal valves will have two hoses; one hooked to a vacuum source (carb or manifold) and the other end hooked to a device (diaphragm, vacuum motor, cannister, etc) If neither end is hooked up you will have to make sure any source is capped.

[Fiat88]

I'll take some pics tomorrow and maybe you can help me out further. I have an automatic trans. and have another question about the following steel line:


I remember you telling me in another post that: "the tube is the vacuum source for the modulator, which makes the tranny shift. It has to be hooked up to manifold vacuum". I'm having trouble finding where to hook it back up too. Still learning. Thanks for the help.

[So Cal Mark]

there should be a nipple just forward of the thermovalves for the tranny tube. You'll need a short piece of vacuum hose to connect the two