Dieseling,is also called run on.
The biggest two contributors to run-on, are hot-spots in the combustion chambers and too-far-open throttle blades.
The too-far-open blades are because of either A) design, or B)faulty components; and/or incorrect carb adjustments.
As to A), the design. When the idle timing is retarded,As these cars are,the idle speed goes down.The only way to keep the engine running is to increase the throttle opening, to get the rpm back.
As to B), When certain components fail,the idle speed goes down, often stalling. The typical cure is to crank up the speed screw.
Hot spots in the chambers are just that. The usual contributors are overheated sparkplugs or carbon.
Overheated plugs can be due to; lean running,wrong heatrange for current usage, or faulty cooling system.
Carbon. Well where does it come from? It comes from either fuel or oil. Tired engines create it as a matter of course.But the biggest contributor is the carb.And, in the carb,the offender is often the choke. If the choke fails to come off in a timely manner, carbon is the result.The choke failure can be due to; a plugged heat passage underneath the carb in the intake manifold, or the bi-metal element or its heater or the timer(if used). Occasionally linkages stick.
Fuel is rarely a contributor, although it is often blamed.
-The passage under the carb is often plugged by about 110,000 miles.This passage, is often the source for pulling EGR, so it's easy to test to see if it is plugged. The test will not prove it is severely restricted.With engine idling simply apply full vacuum to the EGR valve.The engine should stall.
-Carbon in the chambers can be removed chemically, with good results. The fastest method involves pouring it down the venturies at a fast idle. Other chemicals go into the fuel tank.
-Towing, high-speed running, and too-hot engine , can overheat the plugs. Pull a couple the next time it happens and check 'em.Cooler running plugs are available.
-FWIW; ethanol-blended fuels run cleaner. The more ethanol the cleaner the burn.I like these fuels.The 10% stuff is real easy to tune for, and has caused me no trouble.I have been running it in all my engines and equipments since it was first introduced here in year 2000.
Well that should keep you busy for awhile,lol.
p)
