Rattle under load when engine is hot

[Bora Sport]

If you rev the engine up slowly from idle with the car stationary and in neutral or with the clutch in (same thing) ie not driving the car down the road and the rattle is there then it is not pinging. It is something rattling like a heat shield on the down pipe or the shield on the cat. Or it could just be some part of the exhaust system.

I would be checking all the easy things first before blowing 1000 bucks on an almost certainly uneeded decarbonising. Our Vento has done over 350,000k's and it has no problems with carbon in the head. It does have that rattle though which I know is the heat shield.

[Bug_racer]

no one has suggested checking ignition timing ? Some Golf 3's you can change timing slightly .

Also what about checking the knock sensor itself ???? It could be giving an incorrect signal to the ecu which in turn controls the mapping for timing !

Another thing to check would be the air intake temp sensor on the airbox .

Fuel could be another issue , fuel pressure ok ? fuel pressure under load ok ? injectors blocked ?

So many things to check before de-carbonising the head !

[jmystaki]

Ok.... had the head and valves decarbonised, the injectors cleaned...little or no change... $200 later....

Not happy JAN !

My "guess" is that my knock sensor is faulty

I will wait for my VAG-COM cable to come in the post, that will allow me to see if the knock sensor is working and if the timing is being modified when pinging...

[Biggles]

What software do you have to be able to analyse the golf's computer?

[Jmac]

Bug Racer has hit a valid point, if its had a cam belt lately the dizzy could have been moved a couple of teeth and like he says the timing can be adjusted. You can check the knock sensor with Vag Com by tapping the block and watch it register.

[jmystaki]

Thanks for the advice re: testing knock sensor. I hope to get my cable in the next day or early next week.


Hi Biggles - I will be using Ross-Tech - http://www.ross-tech.com/

Cheers

[Tim]

if u think its pinging cant u just retard the timing a little and see if it still makes the noise?

[Bora Sport]

Have you tried free revving it yet as I suggested? It will cost you nothing.

[jmystaki]

Hi Bora Sport

There is no rattle when free revving... only under load (most often 4th gear, sometimes 3rd gear) ((automatic)).

Last night I put a clamp on the top of the down pipe... still made no difference.

I did notice that with a reasonable push on the downpipe heat shield there was some movement, and wondered if the dynamics of this movement changed when the temp rises (hot engine).

Question for all - people suggesting the heat shields and down pipe shields, does this rattle normally occur all the time or only when the engine is hot?

For me when the engine is cold, I don't hear a pip !

Cheers

[Jmac]

And to add to the mix this is when you will hear an exhaust noise most (COLD) so it isnt that mate. Back to fuel and timing mate
Jmac