Chrysler Repair: rpm surging: 93 chry new yorker, throttle shaft, accelerator cable

Question
after reaching approx 35mph,-then releasing accelerator , motor keeps 30to35 speed. then when stopping, brake is fighting engines cruise control type of surge. (pulled c.c. fuse)        
taking foot off brakeafter stopping...
engine will run up to 30+ mph w/o even touching accelerator - and stay there. grrrr, as if on cruise control.   replaced idle air control motor, temp sensor, throttle pos. sensor, cleaned throttle body-inc. idle air pintle area. no vac leaks, accelerator cable not sticking. this intermittant prob. happens after engine load, (steep decline, passing) and when outside air temp. is 70+. no prob in winter. i live in michigan. diagnostic box ck. for both engine and transmission revealed nothing. on board diag ck. throws no codes. has anybody ever delt w/ this? please help.  

Answer
Hi David,
It almost sounds like the throttle valve is sticking open perhaps due to wear on the throttle shaft/throttle body interface (like carbs would do) so that even though you cleaned it there may be mechanical binding. I would try to inspect the position of the throttle shaft at the time this is happening to see if that might be the case. Other than that, an undetectected vacuum leak is the other possibility. Have you tried tracing all the vacuum lines using the under hood sticker as a "road map". You can even try spraying small squirts of carb cleaner (etc.) on each joint/line/module in that system to look for a hidden leak. The idle speed will jump momentarily if you spray the site of such a leak.
Those are my thoughts. Let me know when you find the cause so I can share it with others.
Roland