- My model of MX-5 is: ND__
- I’m based near: __Cheltenham
- I’m looking for technical help or recommendations on: _Tappet noise on starting from cold. Disappears after driving for 2 or 3 minutes.
“They all do that, Sir.”
That’s the Skyactive engine changing its working mode. Here’s Mazda’s explanation of their ideas
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THat’s the default dealer gaslighting line 
But yes, tappaty sounding on cold start up. I don’t just drive off when I start it up, but let it sit for a minute or two.
Thanks for that. I tend to do the same and give it a minute or two before I drive off. I was just a bit worried that it could be a problem that could do damage if it’s not sorted. It’s a 22 plate with 24K on the clock, so I wouldn’t have expected it to be wear related. Oil change 2K miles ago.
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i seem to recall some wording somewhere, that its the (direct) injectors on the skyactive making that noise.
Interesting. So if that were the case would in stop after a couple of miles? One thing I didn’t mention was that the tapping is directly affected by engine RPM, but I guess it would irrespective of if it was the injectors or the valve lifters. Like I mentioned, my main worry is whether I am doing any damage by driving it, given that it quietens down quite quickly. I don’
t want to waste money asking the dealer to look at it, if it’s normal.
if in doubt, get a sound clip and upload it 
I went to buy my 2019 ND2 in September and the tapping noise on start up worried me. I asked to start the one next to it to see if it was the same and it was, Loud tapping while the blue water light is on, once this turns off it quietens down. Sounds like rod knock if you didn’t know they all do it.
I read somewhere it was about varying the combustion mode between Atkinson and Miller cycles, but I can’t find that reference on a quick search so I don’t remember which way round it is.
Hence my post above pointing at the Mazda bit, alas it carefully skirts around the apparent negative effect if you don’t know what you’re looking for.
It is because on a cold start the combustion chamber, incoming air, atomised fuel, etc are too cold to support the normal (hot) running with spark-assisted compression (almost diesel-like) ignition on a lean mixture. See that clever diagram in the Mazda bit.
So in this case the mixture is richer, and the spark is essential, and the various timings are fiddled to be more like an old-fashioned petrol engine, but it still has the high compression ratio, hence sounding diesel for a few seconds.
The -X engine with the sensors inside seems to be the future if it can minimise the big change in mode that is all too obvious with the -G variant on our 2016 Mazda3 initially sounding like a diesel, as heard every cold morning for about fifteen seconds.
Because it has a louder lifer sound than the Skyactive G?
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Thanks to all of you guys for your responses to my question.
I’ve only just joined the club, and have quickly realised that it’s a great supportive community.
I’m sure it’s going to be worth every penny of the annual subscription!
Best to all!
Mike
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The MX-5 has never had the SKY-X engine, they are all SKY-G.
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Oops, my mistake! I’ll remove that mention.
Thanks Robbie, I wonder where I read that “fact”.
Probably the internet, we all know that half of it is wrong and the other half is made up don’t we?
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When my 1.5 ND starts up from cold it makes a right racket. I quickly realised (from a post on here) it’s something to do with the electronic choke, if I remember correctly, so normal. That lasts about 5 seconds, I thought at first it was a problem.
My 2021 Renault had a really annoying tapping sound when cold.on the advice of a friend who has a repair shop I added wynns injector cleaner to a tank of petrol. The tapping has now disappeared and the engine is much smoother and quieter.the car had covered approximately 30000 miles! It took about 300 miles of driving for the cleaner to take effect.
When it’s being ‘tappety’, do you find the noise is slightly louder if you drive off/put the engine under a little load to move off?
Mine does this, but can’t be reproduced after maybe 1/4 mile or less. To me it’s almost like a bearing knock noise?! I have a ‘23 car that’s done about 11000 miles.
I am just glad its not a 13B fitted
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There are two noises when the ND is started up from cold. There is an initial sound like a blown exhaust that last for about 10 seconds or so, which is a function of the emission control system. Then you will notice what sounds like noisy tappets which doesn’t go away until the engine is fully up to operating temperature. Causes of this noise could be the tappets, fuel injectors or piston slap. It is most likely to be the tappets. If it is piston slap this is due to the pistons being very short to reduce friction and oscillating mass (to reduce frictional losses and help fuel consumption). The clearances reduces as the engine warms up and the piston slap disappears. I know this may be speculation but I have heard of all three reasons being suggested. It has happened on all three of my 2.0 litre NDs and it is nothing to worry about.
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