Question:

The vehicle was designed to run WITH the octane shorting bar in place.  If it pings with the bar plugged in or with it out, it needs to be repaired. Either you’re using cheap gas or there is a condition that causes carboning in one or more of the cylinders that should be investigated.  If it is still in 5/50 warranty, return it to a dealer for the work.  If the bar is removed by the way you may notice da decrease in MPG. L.H. BLUE OVAL SERVICE MKE,WI

Response:

I recently had my 1994 Explorer (4.0 liter) in for service with a pinging problem.  The dealer told me they removed an Octane Rod from a wiring harness in an attempt to solve the problem, since there is no way to adjust the timing.  So far I haven’t noticed any pinging since the service was done.  However, I have no idea what an Octane Rod is!

Response:

Yes, there is an octane jumper on my 1992 XLT Explorer  with 4.0 L engine.  It is located behind the Power Distribution Box on the passenger side (under the hood of course) and is also near the fan motor for the ventillation system.  It is merely a two wire connector ( one solid green wire and one gray with red stripe wire).  There is a removable gray colored plug which can be removed from this connector.  It does apparently work such that engine ping can be reduced or eliminated.  I use 87 octane Chevron gas and have driven with this plug removed for 4 years with no down side.  To protect the now unused electrical contacts, I sealed the connector with a plastic vinyl cap to seal out road grime, etc.. By the way, I do have one gripe about my Explorer.  The A/C is slow to cool and blows very warm air after the car has sat, say after returning from shopping.  Somewhere on the internet I read that this may be due to the fact that the underdash box where the heater core is (which is also where the a/c evaporator core is) is not regulated by a mixing valve. Therefore, there is always hot engine coolant present in the same box where the cooled air passes and thusly needs to work harder to cool the chamber’s heated air.  This has been the case since I bought the vehicle new. Dealer said it is normal.  Sounds like a design flaw to me.  Any input?

Response:

 > I recently had my 1994 Explorer (4.0 liter) in for service with  > a pinging problem.  The dealer told me they removed an Octane  > Rod from a wiring harness in an attempt to solve the problem,  > since there is no way to adjust the timing.  So far I haven’t  > noticed any pinging since the service was done.  However, I have  > no idea what an Octane Rod is! It’s called the Octane Shorting Bar and it retards the spark about 2 degrees.  It is a very common mod and was discussed extensively in the mailing list back in 1994.  No ill effects were reported.  Some people even remote out the the shorting bar to the cab.  So that they can get slightly better economy under light to moderate load by switching the shorted connection on and off when the engine is under heavy load.  The best of both woulds. I haven’t remoted the bar, but if I were to do so, I’d use a small twelve volt relay close to the harness location and tie the primary into the 12V+ engine "run" curcuit.  This way, you are almost 100% safe in keeping the computer connections isolated if ever you have a wiring problem.  Cheap insurance…       Home Page:        http://www.users.cts.com/crash/m/mikey

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