Keviwe

03 Max, 104,000 miles (mostly highway), new NGK platinum plugs (Nissan recommended).
Engine just recently began pinging (spark knock, detonation) between 1,600 to 2,000 RPM under light acceleration when engine is HOT. It does not ping until it's good and hot. It pings more right after I get off the highway (running at 75 MPH for hours). Engines get a bit hotter right after getting off the highway. I think this ping is temperature related.
I have tried all brands of fuels and octanes and also ran a couple of bottles of Chevron Techron fuel system cleaner through the tank. None of this made any difference.
I also replaced the spark plugs with Nissan recommended NGK platinums and the ping went away for about two weeks then can back.
Does anybody have any TECHNICAL suggestions?

Galo

Try running some Seafoam thru the intake system to clean out/decarbonize the tops of your pistons. If that does not work, replace your current spark plugs (again) with the same type plugs but one heat range colder.

GBAUER

iTrader: (2)

I did the seafoam and changed my plugs also and had the same problem come up after two weeks as well (came back with revenge! It's worse now than before). I think the problem lies elsewhere with the 5.5 gens. There's been several posts on this and, to the best of my knowledge, nobody has a good solution yet. If there's anyone who has a better idea than changing the plugs or who actually knows the cause of the knock, please speak up! My head's rattling here!

Galo

When you pulled the plugs, were they of medium-to dark brown color or where thet very light brown or even grey-ish? Anything lighter than a medium amber is indicative of a lean burning condition and abnormally high combustion chamber temperature which on a Max may be caused only by one of the four following conditions:
1. a marginally bad MAF which could be signaling the engine ECU that the engine is receiving very low density air, as if the car were in a high altitude environment, which causes the ECU to lean out the mixture to the point the car begins pinging, knocking, etc

2. A marginally bad O2 sensor (or sensors) which are telling the ECU the mixture is richer than it really is (more CO2 than is really there) to which the ECU responds by leaning the fuel mixture with the same results as in Condition 1 above.

3. A marginally bad intake air temperature sensor (called a thermistor) which is telling the ECU that the incoming air is much hotter than it really is, that also causes the ECU to lean out the fuel mixture, resulting in the same thing as in conditions 1 and 2 above

4. A bad engine water termperature sensor -but that would only cause the ECU to enrichen the mixture (such as when the car is cold) and that would prevent pinging and detonation so that's not it.

If you have the specs, troubleshooting skills and tools to test the nominal output signals of these sensors, have at it and you might find the cause.

But, I will bet you a lobster lunch that you will find all of them within the ranges of the specs -but leaning towards one side of their ranges versus the middle of the range, and that side they are leaning to is the side of the range which drives the ECU to a slighly lean condition versus the opposite -which would tend to inhibit pinging and detonation.

Bottom line, this indeed could be a nightmare to trouble shoot. I would start by the simplest route which is to install plugs one heat range colder which will make the engine less sensitive to slightly higher than normal combustion chamber temperatures. I forget what number the OEM plugs are, but if they are NGK or Denso or any other Japanese plug, the next colder heat range plug will be one number higher. For example, if the spark plug is a 'abc7def', install an 'abc8def' -the same type plug one number higher. Most likely the dealer wont have them and you'll have to buy them at Autozome or whatever auto part.

If that does not cure the problem, step 2 is to go to the dealer and have them go thru the individual -and expensive- 'sensor measuring' process......maybe they will find one so obviously skewed towards one side of it's nominal voltage output range that replacing that cures it.

Step three is to have the dealer dial back (retard) the timining a bit using the Consult II tool. Most likely it's at 15 degrees BTDC, you may need to have ir dropped a degree or two -but that will also cause a slight loss of fuel economy and responsiveness, so....that's not the desired alternative.

My bet is that the one step colder plugs will fix the problem. Well, they wont exactly fix the problem itself but they will compensate for it . Do that and post back results.