Technical Intermittent low warm idle

[hammer67xke]

I have a 1980 fiat 124 that has a carb, and automatic transmission. At times after engine is warm the idle is 800, and intermittent at stop lights the idle goes to 350-500 and seems rough. It has just seemed to start this issue. I have replaced the spark plugs, nothing greatly wrong with them. replaced the wires and cap and rotor not long ago. Last year I replaced the fuel filter and lines that were deteriorating. I think this is a separate issue but let you decide. I have bought two fuel check valves and have not installed them yet. For over a year, if you wait over a week to run the car, it seems like the fuel drained back to the tank. Mechanical fuel pump. It will initially start from fuel in the carb, but then will need to crank to get fuel back to carb. I included that incase it means something that could pertain to the intermittent low warm idle.

 

[bugsymike]

I have a 1980 fiat 124 that has a carb, and automatic transmission. At times after engine is warm the idle is 800, and intermittent at stop lights the idle goes to 350-500 and seems rough. It has just seemed to start this issue. I have replaced the spark plugs, nothing greatly wrong with them. replaced the wires and cap and rotor not long ago. Last year I replaced the fuel filter and lines that were deteriorating. I think this is a separate issue but let you decide. I have bought two fuel check valves and have not installed them yet. For over a year, if you wait over a week to run the car, it seems like the fuel drained back to the tank. Mechanical fuel pump. It will initially start from fuel in the carb, but then will need to crank to get fuel back to carb. I included that incase it means something that could pertain to the intermittent low warm idle.

To me it does sound like a carb or auto choke problem, unless you have an air leak, possibly the vacuum to the brake servo as it happens when you stop at lights etc. making fuel mixture weak on idle?
In the same vein, if yours is a single twin choke carb, Dellorto or Weber, around 1980 when working for a Lada Dealership (Fiat 124 under license) the idle jets had a tendency to collect water and dirt. You could undo the jets to clean them but the emulsion tube below it often had dirt also, it was possible to lift them out using a match stick then if you tapped them gentle on a hard surface dirt or water would come out.

 

[hammer67xke]

To me it does sound like a carb or auto choke problem, unless you have an air leak, possibly the vacuum to the brake servo as it happens when you stop at lights etc. making fuel mixture weak on idle?
In the same vein, if yours is a single twin choke carb, Dellorto or Weber, around 1980 when working for a Lada Dealership (Fiat 124 under license) the idle jets had a tendency to collect water and dirt. You could undo the jets to clean them but the emulsion tube below it often had dirt also, it was possible to lift them out using a match stick then if you tapped them gentle on a hard surface dirt or water would come out.

thank you for more directions to inspect. cars can have common issues. a mechanic on general equipment said, try a carb idle solinoid, and pulled up one on the car. I thank you again for tendency to colllect water.

 

[bugsymike]

thank you for more directions to inspect. cars can have common issues. a mechanic on general equipment said, try a carb idle solinoid, and pulled up one on the car. I thank you again for tendency to colllect water.

Long time since I worked on them , has yours got an idle solenoid, the Ladas around that era didn't. Some other cars around then did, the had a lucar connector on to a barrel solenoid screwed into the side of the carb, if the wire made a poor connection they could stall. I think the idea of that idle solenoid was to force them to stop when you switched off to reduce running on as they made cars run leaner on the fuel.