Rattle under load when engine is hot

[sydVR6]

The only other things I can think of at this time that might have an effect would be mixture related.

- O2 (lambda) sensor?

- MAF sensor?

Bear in mind that these would only effect the performance of the engine under normal operating conditions (when the fuel injection systems run in closed loop mode).

When you're using wide open throttle, the O2 and MAF sensor outputs would be virtually ignored and the engine would automatically enrich the mixture to protect the engine.

[jmystaki]

I have previously posted group 1,2 and 3 stats... including O2 Sensor...


I need some feedback on these results.... not sure if they are right...

[Jmac]

Lambda probe reading wil roughly let you know whats going on during a real time event and only in closed loop. Open loop forget it. Mate you might have picked up a bad batch of juice. I would drain the tank and fit a new filter and fill with good juice. The o2 sensor reads the amount of oxygen in the exhaust , for example if it has 0% oxeygen it is running Rich which produces a high voltage (0.7-1volt) Now the o2 sensor only goes into closed loop when the coolant temp sensor is happy the engine is at operating temp. At idle and part throttle is then when the measuring is done. At full throttle the o2 measurements are ignored by the ecu. If you think you are running lean mate you should notice an increase in temps. Blocked injectors, blocked filter and extra air entering via a Vac line or something being split. Lambda probes are great for 100k but then can get tired and give whacky signals as does the MAF too. Bad juice and crappy filter is common. Tired o2 sensor common too.
Jmac

[Bug_racer]

I cant believe this still hasn't been resolved !

Just putting up my original post so you can try the other things I mentioned . Maybe I need some more rep points so people will take notice ?

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 !

[Jmac]

I cant believe this still hasn't been resolved !

Just putting up my original post so you can try the other things I mentioned . Maybe I need some more rep points so people will take notice ?

Cmon dont upset they guy do as he says!!! Check what he has recomended

[Golf Loon]

If you read all the posts, it says the timing has been checked.

I re-checked it and recommended he change the knock sensor.

[jmystaki]

OK

Knock Sensor ordered from the US....

Already in shipping... should get it this week....

[jmystaki]

Brand new Knock Sensor installed, still pinging........

[jmystaki]

ok, flushed the tank and check the fuel filter (new one installed in the last 12 months - genuine Bosch).

Just did 2000km (return the Melbourne from Sydney) thought it may clean up the engine...(possible more carbon in the head, causing high compression, therefore causing pinging....)

Still pinging !!!

Despite the temp gauge in the middle of the range, I think it is running a little hot, and therefore a bit lean.....

Suggestions?

[sydVR6]

Ok.

When plugged into a VAG COM scanner, is it throwing you any codes?

Other than that, If it's leaning out enough to ping, there must be an obvious reason as to why... somewhere. Even with the new knock sensor, your bosch system isn't retarding the timing enough to stop the pinging. I'm wondering if the ECM is reading ok.

I think it might be time to talk to the EFI gurus, whoever they are : )
I know of a good bunch (Petroject.com.au) who consult on this type of thing.

Have you tried seeing what happens when you run a (Wynns, Nulon) Octane Booster with your tank of 98 octane fuel? Theoretically, that should at least help it to stop pinging.

Have you done a check of your fuel pressure regulator or had the injectors cleaned at all?

BTW What happened when you went to have the head de-carbonised? Was that done for you in the end? If you want to try something like that for yourself, you could do the tablepoon of brake fluid in the chamber trick.

It's pretty easy - remove the plugs, spoon or syringe a tablespoon of brake fluid into each cylinder through the plug hole, crank by hand for a cycle or two, then leave overnight. Replace the plugs, fire up engine, watch the masses of smoke pour out for a (scary) minute or two then take the car for a spirited drive. This recipe is sometimes recommended for bore glazing and the like, but also removes a lot of crap from your upper cylinders and plenum chambers, so, it could be worth a go (if you haven't already had the de-carb). Of course, be it at your own risk, but plenty of pretty safe minded heads have tried it over the years and had good success with gunged up cylinder heads. The brake fluid won't harm anything inside the bores, but sure does get rid of any crap!

Sorry for the lack of 'structure' in this reply, here, but it's late : )