any tips on how? where was the leak on the intake manifold?

did it only occur under light throttle? I wonder if the vacuum leak from the intake manifold would result in leaner (more engine ping) condition under more load?

The amount of air that leaks is dependent on the difference in pressure (delta P) between manifold and ambient. Delta P is lowest at WOT, so the least leakage occurs.

Post a Video.......

First question. how many miles on the car (carbon build up)? Do you have access to a scanner with data access to see knock counts? Are you sure it is knock and not something else like an exhaust leak, not common on this car from what I've read but have had some pin hole exhaust leak that can sound like pinging under part throttle load.

I don't have a scanner. It is my wife's DD and the ping started around 60k miles under condition described on the first post. It occurs intermittently and can't be reproduce at will (unfortunately).

Carbon build up was my first guess. We ran through many different kind of fuel cleaners but didn't really help much. However, it may not be the cause since it doesn't occur under load.

As for exhaust leaks, should be noticeable at idle during the cold start? Engine idles smooth and quiet under all condition.

Hey, I just posted this in another thread. Recently bought a 370 and have some pinging too under light throttle + some engine load. Found this in the manual: "Now and then you may notice light spark knock for a short time while accelerating OR driving up hills. This is no cause for concern, because you get the greatest fuel benefit when there is light spark knock for a short time under heavy engine load." Seems to be normal if nissan has it in the manual

That's interesting... it said under heavy engine load.... curious if taking off is considered heavy engine load?

Is your an 7A also? How do you get rid of the engine ping? My wife usually just let off the throttle for like a second and it would be fine afterward. It never occur once it gets going or any other gear higher than 1st.

Usually if it pings it tends to be part throttle load right at tip in for most cars and will go away as soon as the load is less and ign correction occurs. I see you live in socal so you are warmer climate and 91 octane. I have been told the z is actually designed for 93 octane and they do have a constant ign correction with 91. I never heard any ping with mine in oem tune but you live right by one of the best tuners, may consider going to him (Seb) for a custom tune as they actually take out some of the ign advance for 91, if it really bugs you. Otherwise it is most likely doing as designed, going to the limit and then backing off when it detects knock. It's hard to say without being there and hearing it.

According to most, the best way to get rid of it is higher octane fuel. Another option is to get on it more in first- you're wife may be lugging the engine a little. I can't say for sure, but the situation your wife describes may constitute a heavy load.

Mine is a 6MT. I notice it in 2nd + 3rd when lower than 2k RPM and evenly accelerating. Anytime the load is lessened it stops.

Also, if you're at 60k, it wouldn't hurt to replace or check the gaps on the plugs.

that sounds logical. It probably got worse with some carbon build up due to higher mileage. Fortunately, it only occurs during initial take off rather than pinging at higher rpm/speed.

Curious if it would cause engine damage with the 'as designed' ping in our situation?

Looks to be similar condition.

can you recreate the ping at will? how many miles do you have?

This is what I meant when I said most cars I have worked with (so that's not the z as I only have my own for comparison) but if they ping it is right at throttle tip in from cruise and is momentary. Typically this is in a part of the map with high ignition timing as they want good throttle response and max torque since you are trying to accelerate. Not every car does it even within the same type of car and climate and fuel quality play a roll (acura MDX were fairly picky since they are also heavy and use high comp ratio as well). As for long term damage, not being able to hear if yours is a light ping that instantly gets corrected or if it's bad knock and not correcting would make a big difference, the first one I personally have not seen one fail catastrophically by light ping that gets corrected quickly.

Again if you really want it gone I would go to Seb and he will actually tune it for 91 octane with two ign maps one for summer and one for winter (hot climate/cold climate).

I can recreate it on essentially any incline. It's very light pinging. Not the kind of pinging when you almost stall this car if it's a MT.

I have 7000 miles.

great explanation. it is a quick metallic ping. it goes away as soon as she lift the throttle and re-accelerate fine within a second or two and runs well from there at any speed.

Again, the engine is quieter and smoother than my newer/lower mileage Z. And the exhaust also sounds much better, but that's a different discussion ;)

Our main concern is the long term effect of this issue. The ping normally last just 1 to 2 seconds at 1500 rpm or less.