Brought my 2005XS Forester to Liberty Subaru on Tuesday for continuous ping problem. Service manager drove car and agreed that there is a problem. Checked codes, said everything is in spec. Returned car Thursday so Subaru factory rep. could look at car. Drove car 30 miles with instrumentation attached. I was told that the car performed completeley as designed, and that there was absolutley no pinging. Service manager told me to bring car back in warmer weather to have Subaru test again if ping continued.

 

Odd thing is, after pinging from day 1, the car has not pinged once in three days. Suspect the computer code was flashed. Any thoughts? If so, why wasn't I told?

Ping can be hard to reproduce. usually going down a heat range in the plugs will correct the problem. They may have flashed it but i doubt it.

 

nipper

Ping can be hard to reproduce. usually going down a heat range in the plugs will correct the problem. They may have flashed it but i doubt it.

 

nipper

 

Here is what I don't understand. The car has an adaptive system that adjusts timing based upon signals recieved from the knock sensor. If the system is working properly, timing should be retarded when pinging is detected. Why shouldn't a properly working system correct the problem? Why substitute a different spark plug?

Because the ping is coming from the plug body, not from poor gas, which is what the sensor is designed to deal with. The knock sensor cannot adjust for a mechanical cause of ping, as much as it may try. I have posted many times on here links expaling spark plug heat ranges. A cooler plug retains less heat, so it reduces and can cure ping. a hotter plug retains heat.

Also ping from the spark plugs comes from the spark plug body retaining heat. It is considered harmless (except to the plug), but annoying.

 

nipper

Here is what I don't understand. The car has an adaptive system that adjusts timing based upon signals recieved from the knock sensor. If the system is working properly, timing should be retarded when pinging is detected. Why shouldn't a properly working system correct the problem? Why substitute a different spark plug?

The knock sensor is pretty crude, it doesn't always hit the threshold on every engine that comes off the production line. Even if it IS functioning OK, it still has to hear knock before it can react - at which point it throws a corrective "bulk retard" at the knock. Then it creeps back up to normal at a preset rate.

 

My advice? Drive your tank down to empty, then fill back up with same fuel you normally use and see if the knock comes back. It wouldn't put it past the factory rep to have added an octane booster just to get you out of there.

 

It's gonna take a while to purge the GM culture from this once progressive organization. Use stop leak product to fix head gasket. :-\

 

**** ******!