Engine intermitten knocking sound?

[Kianbeng]

Hi all,

 

Need to ask a question. Today I was caught in a traffic jam. Very sian. And I heard something like a knocking sound from engine esp when I halfclutch and move off in 1st gear. Then after a while I realised this knocking sound is intermitten and most of the time comes when the car is idling. And when the knocking sound is heard, I can see the idle RPM drops very slightly. And when the knocking comes, it's consecutive for 5 knocks or so and then ok for next 20 seconds or so and then you hear it again.

 

So now getting worried. Called my mech on the spot and ask what possibly could be the prob. Me very busy recently and can't visit him. Flying overseas tonight and coming back next week also. Basically he said it's likely to be a "electrical" problem. ie spark plugs, wires, blah.....

 

Spark plugs I just changed 5,000KM ago. Although it's cheap ones...can't be so fast bah? After some searching online now, I'm wondering if it could be the O2 sensor or knock sensor? But I'm driving a Mazda323 2002 model. How to find out if I have these sensors in the engine? My model should be quite basic one...no intelligent computers I think.

 

Appreciate any advise / suggestions.

[Yeobh]

I reckon the noise may have come from your clutch assemble, pilot bearing or thrust bearing. Maybe the clutch is already very much wore out and tend to slip when you moving from stationary position. The noise maybe form the clutch assmbly springs

[Elfenstar]

In addition to what yeaobh said, faulty EGR???

 

Its very hard to diagnose over the internet, not to mention we don't know where in the engine bay the noise is coming from, etc...

[Kianbeng]

Hi,

 

But the sound also comes when idling leh. I also got test with or without clutch depressed.

 

Furthermore, the clutch I replaced it 10k ago only. Clutch bearings, plate, disc. But actually after replacing, I also feel theres some vibrations when moving off at gear 1. Or half clutch. Can feel as if the plate is not even. But I changed the plate leh. Everything is original except the plate was OEM. But should be alright one right?

 

The knocking sounds are quite faint one...as if someone knocking on the engine softly. "kok kok kok"...then no more.....then "kok kok kok kok kok"......then no more again.

[Kianbeng]

Whats a EGR? Some sensor thingy? When I opened the engine bonnet, it's hard to hear. But when I'm inside the car, I can hear it more clearly.

 

It was intermitten when I first heard it. Now I think the intervals between the sound are getting closer.

[Evildoer]

it could be the part/joints that hold ur engine to the engine bay... experienced this b4...the parts thats holdin/securing my engine has worn out n need replacing...the worn parts cannot secure the engine firmly, when idling...the vibration of the engine cause the knocking sound...

Edited September 28, 2006 by Evildoer

[Kianbeng]

Engine mounts you mean. Quite new also.

[Shahbin]

Hi Kianbeng, a friend of mine suggested the following: If your car is a manual car, have the clutch checked or the ECU unit that is used for tuning the car by a pro mechanic instead.Sometimes it is caused by the petrol having some water mixture but it happens for a short while.

[Elfenstar]

exhaust gas recirculation system. in some cases when the valve fails it makes a knocking noise.

 

You mentioned its harder to hear with the bonnet open but i'm assuming you can still hear it... can you pinpoint where in the engine bay the sound is coming from???

[Kianbeng]

yes I can hear from the bonnet....but didn't seems to come from any other outside parts. Seems to come from inside the engine block.