Chrysler Repair: 2.6 stumbles when warmed up., chrysler lebaron convertible, vacuum leaks

Question
Hi Roland,

Earlier this summer I bought a 1982 Chrysler LeBaron convertible with the 2.6 engine and Mikuni carburetor. The car ran poorly as it sat for a number of years with out being driven. I have put some SeaFoam in the gas and have drove it through 2 tanks of fresh gas and the starts/runs much better. The only problem now is that it will start and idle great when cold and have plenty of power for the first few blocks then it will stumble and have no power between 15 and 40 mph and I need to feather the gas to keep a steady speed. It will still idle good and out on the highway seems to run OK. Seems to be heat related as the car warms up the power goes down. I checked the vacuum lines around the carburetor and they look fine. Any thoughts short of replacing/rebuilding the carburetor?

Thanks,
Jim

Answer
Hi Jim,
I have to admit a lack of familiarity with the Mikuni and the 2.6L engine. I do have the '83 service manual which is probably applicable to your '82. It is impressive how complex these systems were prior to fuel injection. There is no specific diagnosis for that engine, just for all the engines of that time frame.
Because of that many of the suggested checks may not be applicable to the 2.6. Under "engine hesitates when accelerating warm" are:
Faulty ignition, restricted exhaust, restricted fuel filter
Secondary throttle valve binding or sticking open
Check for vacuum leaks, loose carburetor or manifold, Leaky gaskets or disconnected hoses, isolater pad leaking vacuum
Dirt in power valve, channel restriction
Accelerator pump circuit dirty, inoperative pump jet
or linkage misadjusted
Idle transfer system dirty
Idle speed low or incorrect mixture, test fuel pump

I would wonder if the egr valve might not be failing to close when you try to accelerate, which it needs to do in order to circumvent a too lean mixture that would otherwise result. It is a complex test that involves the double egr valves and the thermo valve that also is controlling.
The test is discussed in the manual, see below.

There are about 14 pages all about the Mikuni, and 6 about the egr system for the 2.6. There are 15 pages about the electronic ignition system.
I can xerox and postal mail any of these to you at a cost of 10 cents per side plus the postage.
One suggestion: have you joined the Yahoo Auto group called the Chrysler Lebaron Club? There are folks there with that engine who are smart and would not doubt have some advice to offer from experience.
Let me know how I can be of help.
Roland