"Gentle" Knocking/Pinging on "Tougher" Accelerations

R

reMarkable

Member
(This is for anyone who doesn't ride with the audio system on ;-) )

I have a 2008 Mz5 Sport w/AT with 7,000+ miles. Anyone else hear a "gentle" knocking - pinging, might be a better word - on harder accelerations (or going up a hill or whatnot?) With the Mz5 being a relatively quiet car - I definitely hear pinging that lasts for a one or two second interval when the engine is being taxed a bit. It rarely lasts even a second more than this before the engine seems to correct itself - and the pinging is gone - although climbing a long steep hill, will cause it to often return in 5 or 10 seconds - only to last it's usual 2 seconds or so before being "corrected." I know that a few of my previous cars made mention in the manual of pinging a bit under duress - but don't think the Mz5's does. (Does it?)

I only use brand name gas - and switching brands - doesn't seem to cure it.

Just wondering if anyone else noticed this - or it's just me and/or my Mz5?

Thanks in advance for sharing your thoughts.
 
Try going up a grade in fuel quality (octane rating) and see if it goes away.

Either way it should not really hurt anything, but it sounds like for your conditions the factory ignition timing may be a bit agressive or your fuel is a little lower than the specified minimum octane rating.
 
reMarkable -

My '07 5 Sport 5MT has 9600 miles so far. Same thing happened to me on the tail end of a recent (900+ mile) trip. This weekend, I changed the oil, and the pinging stopped.

Go figure.
 
Thanks for getting back to me folks.

PGCist - you're the first person on this board to say this ever happened to them, besides myself. I had put up another posting months ago - and was shocked to not have five "me too"s. Most of my experiences with my Mz5 have actually not been unique at all - which is a good thing.

I can't recall if I noticed it just before or after my first oil change - where the factory 5W-20 was changed to 5W-30 - which I did at ~5,000 miles. Now changed back to 5W-20 - mileage is definitely up a tad (may 1 to 1.5 mpg) - but this intermittent, very short bursts of pinging are still there.

I'll will try higher octane for a tank for two - to maybe better understand the issue - but I'm not going to spend the extra on a regular basis - assuming no harm is coming of the engine. Also - my mpg is pretty excellent for the type of driving I do - so again, unless I'm harming the engine - I'm apt to live with it.
 
Perhaps your base timing was set incorrectly on your engine from the factory.

I have recently learned that the 2.3L MZR has an adjustable timing pickup.
 
I guess I'll have it checked out - added 2/3 of a tank of Super (93) to a tank of Regular (87) - it definately does less pinging - although I refuse to do this on a regular basis. I will have the timing setting checked. Is this something my local shop can do?

Obviously it's something that would be under warranty if I bring it to Mazda - just wondering if it's quick enough (hence cheap enough) - that I can bring it to my local shop next to work - rather than deal with the difficulty of getting it into the dealer.
 
When you put chronic load on the engine, the combustion chambers heat up very quickly, in which case it can change the octane knocking threshold, which would drive the ECU to pull timing back again. It makes perfect sense. No there is nothing wrong with your car... I dont know why you would want ot get the dealer to pull back your whole timing equilibrium, just because you dont want the car to adjust itself. Remember adaptive timing is and can only ever be reactive, not proactive
 
techspeak said:
When you put chronic load on the engine, the combustion chambers heat up very quickly, in which case it can change the octane knocking threshold, which would drive the ECU to pull timing back again. It makes perfect sense. No there is nothing wrong with your car... I dont know why you would want ot get the dealer to pull back your whole timing equilibrium, just because you dont want the car to adjust itself. Remember adaptive timing is and can only ever be reactive, not proactive
Click to expand...
I agree that the ECU does react and "fixes" it within a second or two most times. I'm a relatively moderate driver and it surprises me that more people didn't have similar experiences.

If and/when it goes into the dealer for service - I'll ask to have someone look at it wrong - but don't want anything done unless I explicitly say so. I get great mileage and don't want it ruined (also don't want to ruin my engine - but I think most agree this kind of knocking is pretty "innocent."
 
me too

this same sound is getting louder in my '08 m5, 8800 miles. has happened since 1st oil change.

any more developments?
 
ofplon said:
this same sound is getting louder in my '08 m5, 8800 miles. has happened since 1st oil change.

any more developments?
Click to expand...

With 13,000+ miles the knocking on my Mz5 '08 does happen more often - and although it still makes the sounds I described above - it's added a subtle variation of the original sound to it's repertoire. This second variant lasts a bit longer and it doesn't necessarily "self-correct" that way the "original" sound does. It seems to happen around 1,600 rpm and also at 2,600 rpm when the engine is under light stress (moderate or more acceleration.) I can correct it by either "accelerating into" it more - or by laying off on the throttle a bit.

Have you noticed any patterns to your knocking?
 
I've had a large number of vehicles over the years do exactly what you're describing, I just haven't heard it in our 5. Having said that, we live at ~4800 feet now, so nothing knocks nearly so much here as at lower elevations where I always used to live.

I would not be the least bit concerned about it unless it becomes more than light. I'll add that the changes you hear are in keeping with the way deposits form in the engine with unleaded gasoline. In the old days of leaded fuel, deposits built up fairly quickly, but reached a level they wouldn't exceed. With detergent unleaded, deposits don't build up nearly so quickly as they used to, but they also either never stop building up or at least build to a much, much higher level. This all means that, over time, you'll hear more and more knock or at least hear it more and more often.

You may or may not be able to reduce the issue a bit with a strong dose of certain cleaners:
Chevron Techron
Red Line SI-1
Lube Control's Fuel Power (FP-Plus)
However, in my experience if you're using TopTier fuel it's unlikely to do much if anything. There's also a water decarbonizing method available, but I won't detail nor recommend it at this point.

If it really bothers you, go have Mazda back off the timing a bit. Otherwise, just leave it alone and enjoy your high mpg.
 
reMarkable said:
Have you noticed any patterns to your knocking?
Click to expand...

my experience is identical to yours. i had a mazda tech drive with me yesterday, and he was clueless about it, said not to worry. this gives me no peace of mind whatsoever...("i don't know what it is, so it's probably nuthin'")

i don't know if you've read my 1st posts on this forum, but i'm the guy who hit a 30 lb. racoon on the way home from purchasing the vehicle new, doing $4k in damage. i may never trust my Mz5 since it was in the shop from day 1...

i'll contimue to update any developments in regarding this issue; hope others do the same.

thanks,

-John

PS - i live @ 5280 feet in downtown Denver
 
don't know how timing works

bulwnkl said:
If it really bothers you, go have Mazda back off the timing a bit. Otherwise, just leave it alone and enjoy your high mpg.
Click to expand...

thanks for your thoughts. can you explain in layman terms how timing works, so i can further understand your diagnosis?
 
I'm referring to spark timing. The spark plug must fire before the piston reaches the top of its travel in the engine in order for the fuel to burn and reach maximum pressure at just the right time afterwards.

If a particular engine has more deposits (very hard carbon build-up inside the combustion chamber) or has a particular deposit that gets red-hot inside the engine causing some of the fuel-air mix to ignite before it shoud (and/or outside the spark plug's control),
OR
If an engine's spark timing is just a little more advanced than most, meaning its spark plugs fire slightly earlier than most,

THEN
The engine will make the knocking noise you hear. It happens when the pressure waves from 2 different combustion points hit each other. This makes the sound you hear. The key is to eliminate the 2 pressure waves and have only the one that the spark plug initiates.

One can have that spark timing retarded just slightly in order to delay combstion just a minute amount. This will prevent the knock sound you hear. It will also almost certainly reduce your mpg, at least it has with every vehicle I have first-hand experience with the owner having it done.
 
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(drive) Thanks bulwnkl & techspeak too for taking the time to share your technical knowledge - I've definitely learned some new things in this discussion. (sun)

For one thing, it's making me reconsider my gas brands. I' ve been buying about 55% Hess, 30% Sunoco & 15% Other - almost always "branded" gas - I can count on one hand no-name fillups in 13,000+ miles. On the other hand - none of these brands are designated "Top Tier" program brands. Would things really be different if I was using Shell or some other Top Tier program brand? (crazy) Should I risk using some deposit cleaner? Could things be made worse - not better? (argh) I believe the manual specifically recommends against additives ("...other than those reccomended by Mazda" - page 4-2 of the 2008 Mz5 Owner's manual.) I guess if I were to try one - I'd go with one that bulwnkl reccomends (posted above.)

Thanks in advance.
 
My wife has on 07 and we have about 17k on it now. I have not noticed any pinging at all. I have been driving it a lot in the last month too. We drove about 400 miles round trip this weekend with a lot of heavy right foot work inlcuding a lot of 80+ mph and even 100. No pinging noticed or retard power loss. Actually only stellar performance.
 
frito - I think most people don't experience it - or it would a be of more topic around here. Maybe there are a few more Mz5's out there with it - but it goes unnoticed, as even at its "worst" - it's a relatively quiet knocking/pinging. If you keep the radio on - odds are, you'll miss it. But for the few of us do seem to have it, we seem to have a pretty common experience.
 
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