I posted this thread in response to another 2005 Murano with pinging issues on a Nissan Help Forum, but so far no expert advise from anyone solving the issues. Any experts HERE???
A friend with a 2004 Murano also has pinging issues. It only pings at part-throttle and only with the engine fully warmed up. Here are some things we have tried and has not solved the issue. Again, we have no codes stored whatsover.
We replaced with new: MAF $500, OEM NGK Plugs PLFR5A-11 $60, cleaned Throttle Body and Reset computer, Reset idle learning, Reset throttle, 2- Fuel pressure regulators $100 + $90, Coolant $10, Air filter $10, Oil change $50, full tank of Union 76 100-Octane unleaded, Redline fuel injection cleaner, Seafoam flush, Knock Sensor $25, changed CVT transmission oil $20/quart, had the Nissan dealer re-flash the computer $300, PCV valve $10, upper intake gasket $10, lower intake gasket $25, coolant temperature sensor $30, thermostat $40. @$$%!
Things I'm considering: replacing all the spark plugs with one step colder NGK PLFR6A-11. Also I questioned the ignition coils, but I have no misfire codes. So I took a coil apart. I noticed that in each coil boot there is a spring that transfers voltage to the plug. Wound in the spring is a resistor to reduce RF Interference. Maybe this resistor heats and fails?? So I will replace all the boots and resistors with NGW 58913. Will follow up later....
Any Nissan ECM specialists on here!!! Here is what I have read/heard from reading automotive manuals, talking to mechanics and racing. When the engine is cold, the ECM is in a specific "map" where extra fuel is introduced. This raises the engine idle during the "warm up" period. Also, several sensors are not active until fully heated, probably retarding the ignition timing. Some of theses sensors, are the MAF and the Oxygen sensors. There maybe others. These sensors require intense heat to work and at operating temperature they probably change the ECM "map" to decrease the extra fuel and fine tune or increase the timing.
Also, the Coolant Thermostat is closed when cold and opens when the engine is "warmed up". The warmed coolant triggers the "coolant temp sensor", which also changes the fuel/timing "map".
Furthermore, ignition coils work fine when they are "cool", but once introduced to extreme heat they tend to fail. Most coils have a primary and secondary winding where the secondary winding cannot be physically tested. A coil will work fine with just the primary winding and you will never know the secondary is not working until the coil completely fails and you get misfires. When our race car is misfiring/running odd we sometimes swap in new coil or ignition box.
All of these Sensors/Triggers could probably be a factor why the engine does not ping when cold and will not ever trigger a code until the Sensor/Trigger has completely failed and becomes non-operational.
Once the engine is "warmed up" all of the sensors become active and the extra fuel is not needed. These sensors(MAF, thermostat, Oxygen Sensor) all become fully heated and functioning. Except the ignition coil, as it does not like heat. Any one of these sensors could be faulty and causing the pinging when the engine is warmed and at operating temperature.
Other factors regarding a constant "pinging" that does not involve cold or warm engine temperatures are mechanical failure. Such as cracked heads/block, blown head gasket, piston ring failure, leaking valve seals, etc...
Because my friend's vehicle does not ping when cold I tend to believe that it is not a mechanical issue with the engine but instead a Sensor or the ECM is at fault. Also when in Neutral there is no pinging. Also, in Drive, if the rpm's are increased above the pinging, the pinging disappears. What mode or "map" does the ECM switch to when going from Neutral to Drive??? Is it variable, does it depend upon engine load/engine vacuum???
These are some of my findings so far. If others have gone as in depth as I have and replaced/tested any/all sensors/ECM on their Murano or VQ35DE, please include more info to this thread so we can solve this. I have also noticed that the same issues are also related to Altima's and Maxima's.
Please help find a cure!!!