Engine ping under light throttle
 

Need some expert advice about this issue. It is for our G37S with 7AT.

The car is totally normal at all time with the exception of occasional engine ping during take off from dead stop or slight rolling with light throttle. Car would start fine, idle and run smoothly otherwise.

We just have to let go the throttle for a second and everything would be back to normal. Engine ping never occur under any other situation. My guess is for some reason the fuel mixture become lean and cause the ping.

I have cleaned the MAF numerous times and run through a few fuel system cleaners already. Fresh air filters and oil etc. Car is totally stock.

TIA.

Get an OBD scanner and see if the ECM has thrown a knock DTC. If not, then I'm guessing that you are hearing something loose in the engine compartment that is rattling around and not engine knock.

No code from the scanner, not even pending. My mechanic did say that the fuel trim indicated lean condition and we have reset the ecu, but condition didn't go away.

It is a fairly fast clicking sound accompanied by a slight engine vibration. Everything's back to normal once you lift the throttle and re-accelerate fine subsequently.

Stock tune? Any mods? Of yes and no, I had this bad MAP sensor on the top of the intake manifold, it made all kind of problems, including being lean then wet, then lean, basically change randomly under load.

If you're knocking, the ECM ought to see it and throw a DTC. So I'm still guessing you have some other problem besides knocking. But that's just a guess.

bad tank of gas, try another brand?

That's what I thought as well, expected to see the warning light on the dash as well as the code, but nothing. The pinging noise only occurs under the condition I described in the above post. The engine is very quiet and smooth otherwise. It is actually quieter than the Z which has less miles.

This has been going on for awhile and we have tried every single brand of gasoline available. The engine is stock.

As for the MAP sensor, can I clean it with MAF cleaner? Looks like it is held by just one screw?

Remembering now, some one came to me with a low rpm engine knock, asked me what is wrong, as i remember the car was at idle and you can hear the valves ticking like a slight knock, then pass 1500rpm it goes away.

Solution, changed brand of oil used in the engine from Valvoline to Royal purple or Nissan Easter oil 5w-30.

The tick was gone, but in my opinion it does that on old oil.(filter is clogged and less oil travel through the engine during low rpm.)

the engine is quiet and smooth during idle or any other rpm. I am familiar with the ticking (vvel) and that's not it. The ping only occurs occasionally during take off from stop or rolling as described above. It doesn't occur under any other situation. I can floor it at 2000 rpm and it runs just fine.

I read a bit about the MAP senor you mentioned. It appears to detect the engine vacuum and send signal to the ecu etc.... Can it be cleaned with MAF cleaner without damaging the internal of the sensor which might contain rubber components? Wouldn't it also throw a P0106 code for the bad MAP sensor?

Nop, mine didnt, i mean it was .4V off, and didnt trigger the fault, it did trigger all O2 sensors like flame.....actually i later found bank two O2 sensor2 was bad, but this due to the MAP being off by a bit and when i floored it at high rpm the fuel delivery is set to 11.40afr(stock), the MAP sensor was flooding it 10.xxafr.....which destroyed my O2 sensor+cat. In any case i was thinking it could have leaned it out and cause slight ping, on load.

In this case get a Torque App and a Bluetooth OBII adapter. Check out ur fuel delivery at these rpms and maybe it might have a the ability to see what the KNOCK sensors are showing.(i dont own the app, i use Uprev tuner.)

Very simple... Don't load up (giving it gas) the engine below 2000rpm. The VVEL runs exceptionally well at low RPMs but no engine likes being run hard below 2k. If it sounds funny, don't run it there. Your're gong to f-up your engine! If you're launching a manual off the line you should be starting at 3-4k and feathering the clutch. In an automatic you can ride the brakes for a second or two to bring up the rpm (while in drive of course) for launch. Don't do it for too long since it's pretty hard on the transmission and will heat up your fluid quickly.

maybe but it is just a workaround for a potential problem...

I'm looking for a solution.

I had the same issue but i'm on Uprev and mechanic made knock sensor more sensitive and it went away, maybe you should try replacing it.

thought about the knock sensor, but the engine shouldn't ping under light throttle condition so the knock sensor shouldn't have to kick in to retard the timing.

furthermore, i think it should throw a code for bad knock sensor?

Mine was doing this once, I had a intake manifold leak, try checking that?