lancesir

I don't know if my engine is pinging but sometimes I hear my engine going "dun dun dun dun...". You can hear it very clearly when idling in neutral. When driving, I believe the sound is still there though mostly masked out by the engine noise itself. I don't think the sound is correlated to the engine speed though.

The only way I've been able to get rid of it when driving is to turn the engine on and off. Is this pinging or something else? I've never experienced engine knock before so I don't know what it would sound like.

Thanks.

Go48

Pinging, aka, pre-detonation, nearly always occurs when the engine is under load. For example, driving up a hill in a higher gear at too low engine revs. Pre-detonation doesn't usually happen at idle, but I suppose if the engine was terribly out of tune with the timing way off that could happen. If you are using a good grade of gas, preferrably 91 or better octane, your engine is in good tune, and you keep the engine revs above about 3K, you shouldn't worry about pinging.

lancesir

Thanks for the info. Maybe it's due to the short shifting I do in the cold when roads are slippery, so I'm driving at ~2k rpm.

Could clogged exhaust be a problem too? On really cold days when I start up I can feel some rumble underneath the car, as if back pressure or something not passing through cleanly.

SOVINE

If it is like a faint popping sound coming from the exhaust when idle I think that is normal with rotary engines.

MazdaManiac

iTrader: (3)

"dun-dun----dun------dun-dun" like someone lightly kicking the back of the car or as if someone was cupping your ears suddenly over and over again.
That is light misfire from the exhaust. It is normal and will only happen at idle (misfire at higher load points sounds different).

"kraaaah" like the sound of a handful of gravel being dropped on your hood from 6 to 10 feet.
That is autoignition (or "ping" - there is no such thing as "pre-detonation" as someone else had stated earlier; detonation is a broader spectrum of malformed combustion that includes autoignition, which is sometimes called "preignition") and is very damaging to your engine.
It is only evident under medium to heavy load and usually between 4800 and 6500 RPM.

lancesir

Thanks for the description mazdamaniac, it's as accurate as you can put it in text

Hmm why is it normal that the exhaust misfires at idle rotaries? If it's true I'm just curious for a technical explanation. But that would seem to be my problem. So is there no way to get rid of it without restarting the engine?

If the "kraah" is pinging, I think I actually heard a bit of that two nights ago, when I drove off after parking in the cold the whole day. That was my fault though, as I rev'ed the engine up cold nstead of keeping rpm's low, oops

MazdaManiac

iTrader: (3)

Rotaries like to idle rich. The PCM tries to keep it very lean, so what you are hearing are lean misfires. It won't hurt anything, its just the nature of the beast.
Imagine how annoying it would be with an open exhaust!

Probably not. Pinging tends to happen on heavy load after the motor is hot in an upper gear. What you heard may have been some other misfire - too rich from cold-start enrichment or an oil injection issue.
Could have even been the ABS/TCS/DSC doing some sort of weirdness.

SOVINE

It would be really annoying with an open exhaust. I have the greddy and it amplified the sound a ton. You can hear it if your outside the car from quite a distance.

vetteman

Thanks for the info MazdaManiac. I've been trying to figure out why my '05 6-spd is misfiring at idle. It just started in the cold weather and its been driving me crazy!

Omega8

So, then maybe that's the "problem" I have been experiencing... Someone tell me if this matches what is being talked about on this topic:

I have a new 2006 GT Manual, less than 1K on it. I notice that when I first start my engine (cold), the idle seems pretty darn smooth, but I can detect an occasional quiet 'pop', like a misfire might sound. If I then give it a little gas (not starting out - just sitting in neutral), as the rpms increase, there's an increase in these little pops . Then, I'll let off the gas, and increase rpms again. Same thing, EXCEPT that it takes a slightly higher rpms to hear those pops/sputter... itr seems to smooth out more, each time. After repeating this pattern a few times over, say, 10-20 seconds, where I give it a little gas in neutral, then let off... the problem seems to dissapate completely. In any case, once I start out moving, there are no problems of this nature.

So, any opinions on this?