Rough idle when stuck in traffic and temp goes up

[grrrdot]

OK,
Hoping someone has some ideas to check.
Car starts from cold great and warms up. Once its warm I push the choke in and the car idles at 950 RPM. I can drive the car on the highway all day long ( just did a 1000 mile trip got ~24MPG ) the temp gauge is rock steady and sits below the half way mark.
When I get into traffic the temp gauge will creep up. If the traffic is really slow / stop and go the temp gauge will get to just past half way and the idle goes into the toilet; 500 rpm, lots of shaking feels like different cyclinders are not firing. I don't see any signs of overheating though, the temp gauge never goes that far past half. Once I get a runway and drive a little the temp drops and the car will idle normal again until the heat creeps back up.

This is my 124 Sedan so OHV 1197cc engine.
Any ideas appreciated!

-G

[vandor]

Reproduce the situation when it idles rough and shut it off and check the plugs to see if it's rich or lean.

[Zippy]

I had a similar problem in my 1800 Spider. It would start and drive fine, but when I got into traffic it would start to overheat and then run real rough. I would have to rev it up to get going without stalling out. What I found; I had a pinhole leak in my radiator. When it cooled down it sucked air into the system and I was low on fluid. In addition, my points moved to the point they were almost closed. This eventually made the car hard to start. The radiator is fixed but the points still move after awhile even though I have tightened them and used Locktite on the threads of the screw. I am living with it until I can convert to electronic. Good luck finding the source of your problem.