What can l do to stop this.l have changed the oil to no avail.A friend told me l should renew the shims is this true.

Teach it ballet instead.

Seriously, it could be the tappets.

Could be the tappets. I'd go to the garage coz it could be a big job

let your wife out of the boot!!

If it is a light tapping from the top of the engine, it is probably the valves either sticking or needing adjustment, or possibly the camshaft is worn, but Puntos do not usually knock out their cams unless they've been abused or have mega-miles on them.
Whatever, it needs to go to a garage.

most probably is the oil pump or in some older fiats the oil spray bar this carries oil to the tappets if its broken or blocked this results in noisy tapping noise almost like a diesel car
warning if it is this do not drive it take it in to get checked or you will ruin the engine

Get rid! lol

If it happen suddenly you could have a broken valve spring. Most of the time it is a valve lifter. If the clearance has worn larger it will hit with a noise. Could have a bad hydraulic lifter plugged up too. If it does not have hydraulic lifters you have to adjust them all the time as they ware.

You may need a valve adjustment - not a huge job, but it can be expensive. The tap sound would be coming from the top side of the engine and have a ''tinny'' sound.

Some symptoms of the valves being out of adjustment would be decreased power, a tapping sound, generally more noticeable when the accelerator is first pressed or released.

what do you expect with a diesel car

u have to be more specific on the noise u hear & when it occurs or dosent.

Tappet noise= usually charecterized by a light regular clicking sound. more noticable dureing idle. is result of excessive valve train clearance.
to check it take of the valve cover get a feeler gauge & check between each lifter & valve or rocker arm & valvetip & match it to dealer specs.

however if its more of a knocking their can be severall problems. Main or Thrust bearing problems. Main Bearing would make a dull steady knock, while a loose Crankshaft Thrust bearing produces a heavy thump on irregular intervals. Thrust bearing u probably would only hear during heavy acceleration
general out come for both replace crankshaft or bearings.

If it is more like a high pitched rapping or clicking noise that is more louder in decelration than u got Ridge Noise. this is less common of all but l see maybe two times.its when the piston ring hits the ridge at the top of the cylinder

If the noise is most commonly heard at idle or speeds over 35mph then it is likely to be the result of worn or loose connecting rod bearings. depending on wear the noise can range from a light tap to a heavy thump

Then u have ring noise which is heard as a high pitched rattleding or clicking in the upper part of the cylinder. caused by worn rings or cylinders, brokern piston ring lands, or insufficient ring tension agianst cylinder walls. correct it by replaceing the rings, pistions, or sleeves or at worst u have to rebore cylinders

then u got piston pin knock. its a sharp metalic rap if really bad it sounds like a rattle.
well basically their r many noises u can hear u need to bring it to a garage to have it diagnosed. from their if u want to replace or rebuild by yourself thats fine. but get the car diagnoised first. good luck