engine runon

[dedmike]

I have an 88 s10 with a 2.5l ironduke.TBI. when I turn the key off it "diesels on" I rebuilt the motor last feb. I changed the coil, ign module, IAC. nothing sems to get rid of it. Any help will be greatly appreciated! thanx!

[KC Ron Carter]

almost all american manufactures had this issue in the early 1970s.

Idle speed it one issue. Lower is better.

The carbon buildup is one issue.

It is a manufacture provided service procedure to flash the combustion chamber with steam to force the carbon to break free from the piston face and valve face.

With the engine at normal operating temperature and approximately 2000 RPM, allow the engine to ingest by a vacuum hose 12 oz soda can of water.

A puff of steam and the carbon is gone.

The ChevRON TechRON is to clean the back side or tulip of the valve
and all components on the fuel path, of varnish.

You can use as often as needed.

This is a must deal if you are near a pinging point and using forced induction.

[AnArKey]

Cleaning the carbon deposits out is always a good thing.

But to attack the problem directly, you could try cutting the fuel. I suspect that on your engine, the injector sprays whenever the engine is turning, irregardless of the key position. Shutting off the key kills the ignition, but the fuel keeps going, and "dieseling" can continue. If you install a relay to cut the power to the TBI injector when the key is off, it should stop.