Does anyone know whether the Octane Shorting Block on a 1993 Explorer 4.0 can be removed with the engine running? Will it cause any damage to the computer? I have to remove it every so often to stop my engine from pinging, so I installed a rocker switch under the dash the in affect removes the shorting block by opening the circuit, this way I don't have to pop the hood. It would be nice to just flip the switch when the engine starts to ping without shutting the motor off. Any ideas or thoughts would be great. Thanks!

 

Pinging on the early 4.0 OHV is quite common, and there are several better fixes than messing with the octane shorting block. Two main causes: 1) Carbon buildup in the cylinders, and 2) Running slightly lean.
1) is fixed by running a cleaning agent (Seafoam is a common brand name) through the engine. This is not a fuel injector cleaner, this is a cylinder decarbonizer.
2) has a few sub-topics:
a) dirty MAF -- causes the computer to think less air is coming in so it feeds less fuel and the engine runs a little lean and pings. Fixed by cleaning the MAF filaments.
b) vacuum leak -- check vacuum and intake tubing and connections for leaks. One vaccum leak that shows up is through the lower intake manifold. Tightening the bolts will usually fix it (they come loose over time), but occasionally the gasket needs to be replaced.

Those issues seem to cure 90-95% of poeple's pinging issues on this engine. Try them and see if yours improves. If not, come back, I know a few less common fixes. If all that doesn't fix it, then you can go back to fiddling with the octane shorting block.

 

Thanks for the reply. I've been dealing with this problem for over a year now and have done the following and still have the problem.
1) Ran Seafoam thru the intake.
2) Cleaned MAF Sensor.
3) Cleaned IAC Sensor and IAC valve
4) Cleaned Temp Sensor
5) Replaced plugs, wires, fuel filter and air filter.
6) Replaced upper intake manifold gasket. and tightened lower intake manifold bolts.

Not sure what more I can do. I'm thinking of installing a 180 degree thermostat and maybe running a set of Autolite APP764's which are a 1 step colder plug. I'd still like to be able to flip the switch I installed with the engine running for those times when it starts pinging too much, but like I said I'm not sure if it will hurt the computer. Right now I just pull over to the side of the road, turn the ignition off, flip the switch and then start the car, but sometimes finding a place to pull over is a pain. Any further thoughts/suggestions would be appreciated.

 

I wouldn't necessarily discount the lower intake manifold gasket. On occasion, it gets bad enough to require replacement.
Any signs of other vaccum/intake leaks? I've heard of some people having problems with the air intake tube developing cracks.
Another fix I saw someone mention is a good fuel injector cleaning -- above and beyond running injector cleaner through the gas tank. If you go to the trouble of replacing the lower intake manifold gasket, part of getting to the gasket is to remove the fuel rail. Get some good cleaner and make sure the injectors are clean while you have them out.
An ECT that reads too hot causes to computer to run the engine lean, so make sure it's reading accurately.
I'm not sure about the long term effects of leaving switching away from octane shorting block. I don't think it would have any ill effects, but I'm not sure.