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My Dec. 2003 Santro Xing, driven 84000 kms is having engine knocking issue.

Once the car heats up (lets say after a 10 kms run), then with A/C on and at a speed above 65 / 70 km/hr, then there is consistent engine knocking which starts and does not stop, even when releasing / pressing the accelerator and the acceleartor press is also adequate.

Got this checked at the Hyundai service centre with below observations :-

Things already in order -
- Clutch overhaul done just 20000 kms before and its fine
- spark plugs changed just 1500 kms before during regular service
- air filter also changed then

Things done for knocking issue -
- Idle speed accentuator cleaned
- air filter cleaned
- System G used in 2 petrol topups

With System G i can see the difference in engine refinement but the engine knocking issue persists.

*** person had suggested that if issue still persists then to change the fuel filter and also get the HEAD (dont know what he meant) cleaned and get the idle accentuator changed.

Pls help as i am otherwise very satisfied with my santro and want to retain it for another 2 yrs of service and am afraid that this knocking may damage my car's engine.

Your santro needs an engine decarb and perhaps valve lapping.

If it has a distributor, try retarding the ignition by a few degrees. This is just a stopgap solution though, and you will still have to find the root cause of the knocking.

Hey namit,

I have faced the exact same issue with my Alto as well for quite some time & it was persistent despite a number of approaches.

One thing however was sure, when the distributor & timing mechanism had been ruled out, that the engine needed decarbonization & there were probably some 'hot-spots' in the engine & excess carbon deposits in the head around the valves leading to a hotter running engine & possible interference with proper valve seating during closure.

The service advisor suggested that we should go in for head cleaning (manual), in which the workshop people would remove the head off the block & clean the carbon by hand & then fit it back. The decarbonization is also done using some chemicals & it had already been tried, but it was not very effective I suppose.

Anyways, the important thing here is that the problem dissappeared post this exercise & the car runs fine. I think you should get this done in your car as well as also suggested by the workshop. But get the timing etc checked.

In my car also, at speeds above 60-70, the problem used to come if in top gear, or it would come even when the revs would hardly be a little higher, say at speeds of 35 kmph in 3rd gear. It had become extremely difficult for me to drive the car. And yes, it can damage the engine but not so early. Just drive it with slight care before the problem is rectified.

Also do not get the timing too retarded as it will affect the power delivery of the car & you also risk burning off your exhaust valve. The immediate effect of an excessively retarded engine, would be loss of power & a burnt silencer (the insides, the muffler etc would be toast). Trust me, I have suffered all this.

Hope this helped.

Regards.

Get a decarbon treatment done. Then you will be OK. Make sure it is from an authorised workshop only. Also, change the fuel pump for the time being. If the knocking stops, then you know it was bad fuel.

for a moment my heart stopped - fuel pump:Shockked: - then realised you must have meant the fuel bunk

1. Change fuel filter
2. Change petrol bunk
3. Change spark plugs
4. Get thorough injector cleaning/decarb

fet yourself liqui moly jet clean,buy two bottles,one use undiluted by plugging the return pipe and feed it thrrough the main pipe,can be done at home.

the second can dump it in the fuel tank and tank up say 15litres and then drive,i have done this a couple of times with cars having a issue with knocking and it has been sorted out.

This is either:

a) A problem with the timing

b) Get the temperature gauge checked. The symptoms you mention also occur when the engine overheats.

c) Adulterated fuel

Thanks all for suggestions.

As adviced, i will go for Fuel filter change and Head cleaning manually.

Will keep you posted.

Hey namit,

Any updates on the car, looking forward to hearing from you on this.

Drive safe.

My bad...i meant fuel bunk!:D

Any updates?

well the same thing is happening with my 800 too, when i drive alone the symptoms are hardly noticeable, but when i am loaded with 1 or 2 person or some luggage...1st gear is terrible....it like i cant drive at all, however on other gears its completely fine....
The vehicle is in very good condition and i want to know if engine de-carbonizing alone can fix this issue, for that i should change my oil also right ?

my car is 42k km run.

When did you last change the oil? Give the car for servicing from a reputed A.S.S. You should be fine.

Today I took my Car for Service, well I didnt do service since i know they will bill this and that and make round off for 5-6k. I did Engine Decarbonizing and changed Engine Oil, for this 2 small thing itself they billed me 1.9k . When i told MASS manager about the knocking and jerks in first gear, he immediately told its clutch which has wore out and needs replacement, i didnt want to be bakra for 2nd time so i told i dont want clutch replacement just do the engine oil change....
anyway car is back and is smoother than before, will check tomorrow with some load and test if its knocking again.