Hi everyone, my NC has developed a pretty horrible knock, it sounds harsher through the phone mic, but in person it definitely doesn’t sound like rod knock. What’s weird is we put a stethoscope on it, and originally there was a intermittent similar knocking noise definitely coming from cylinder 4, but now about 200 miles later, the cylinder 4 noise has subsided and cylinder 1 is making that constant knocking. Do the valve trains ever give problems on these? Is it worth checking out the idler pulleys? Any advice is appreciated. Thanks.
From personal experience check that all the plugs are tight. Check that any senders that are screwed into the exhaust are tight.
I know that taking the belt off and trying the engine for a short time can isolate noises coming from the pulleys.
Have you checked the engine oil level?
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Yep, car has 5-30 mobil 1 in, level is spot on & the car doesn’t use oil, I’ve never had to top it up between servicing it, despite regularly checking.
I will check all 4 plugs are tight tomorrow. I will also take the belt off just for peace of mind 
. Thank you.
Don’t forget any senders in the exhaust manifold. (Three experienced Caterham owners failed to spot a lose sender that resulted in the removal and dismantling of a Rover K series searching for a similar noise.)
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What do you mean by senders sorry?
Like item 2 here Manual pages - MX5 Manual | Mazda MX5 (Mk4) 2015+
This is on the ND but the NC will have something similar that screws into a boss in the manifold.
Ah I did have a o2 sensor replaced only a few weeks ago, definitely worth a check that’s tight. Will check everything else while i’m there. thanks very much.
My money is on rod knock 1&4 from your description and listening to the noise. I’ve experienced 3 and they all sounded less noisy than yours.
Does the MZR/Duratec have a reputation for this in Fords? If the oil has never run low, it seems unlikely.
Sounds top end to me… maybe a lifter failed.
The top end on the MZR is different to the Duratec, but the bottom end is the same. One theory as to why the Mazda engines can use more oil is that they are mostly in private cars bought by older people, and don’t get driven hard enough by their first owner to bed in the rings. Fords, of course, are mostly driven by people who hate them 
The 2.3 MZR is supposed to be the real dog of the range for oil consumption and self-destruction, but it is almost unknown in the UK.
I can’t say my 1.8 uses any oil between services.
I thought another theory was oil surge (starvation). The MZR/Duratec is mostly fitted in a east-west configuration (FWD), except in the MX5 (North South). The theory goes that the baffle plates in the sump are supposed to stop oil surge, but don’t do a good job.
The bottom end is different to allow for the VVT
Pockets in the pistons
It doesn’t matter what CC it is or which car it’s in, they all suffer from the same problem.