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Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 22912
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Hi, my mx 5 developed a "rattle" when it warms up. Sounds

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my mx 5 developed a "rattle" when it warms up. Sounds like tappet's but, after checking all clearances are well within tolerances.
cam chain tensioners are ok also.
can dodgey injectors give the same apparent tappet noise?

a worn injector can be noisy and you could confirm this by by disconnecting the injector leads one at a time and seeing if this makes any difference to the noise

the engine will run on 3 cylinders fine just be a bit lumpy

It would also be worth doing a compression test across all cylinders as they should all be within 10-15 psi of each other
Customer: replied 3 years ago.

in your opinion ,

1/ would 55k miles be low mileage for injectors to lie down,

2/ would they sound like tappet noise if 1 or more were faulty,

3/ under normal circumstances do you get a solid clicking noise from the common rail when the engine is running?


your assistance is very much appreciated.

Hello Paul

yes 55k is low for an injector to fial but if you live in area with dirty fuel, then not impossible either

a heavily worn injector will make more and more of 'click' as it opens so yes the noise is similar to a worn tappet

and there should be no noise from the rail?

if this is the source of the noise ( try using a screwdriver placed in your ear with the blade against the part you're checking) then I'd replace the fuel pressure regulator as this is the only part which could move and generate a noise
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