4age 16v running roughly - diagnostics shows unknown code

[jondee86]

A "knocking", "pinging" or "rattling" sound is an indication that something is not happy in your engine.
There can be a number of causes and depending on the cause the sound will be different, and it will
occur under different operating conditions. Knock from worn or damaged bearings is usually a deeper
sound, like tapping on the block with a heavy hammer, and often occurs when the load on the engine
is relatively light and increasing or decreasing.

Spark or ignition knock (detonation) is mostly heard if the engine is struggling to accelerate under
heavy load at low rpm or when running WOT at high rpm. The sound is more like rapid tapping on the
block with a small hammer.

Rattling may also be produced by other causes. For example I once had a car where the cam belt idler
wore out and started to make a noise. It first started happening as the engine rpm dropped as I slowed
for a traffic light. After a while it was making a noise at idle as well, and even my mechanic thought
it was bad engine bearings until he investigated with a stethoscope.

Unless the engine has been pushed past its limits, bearing knock does not start suddenly. It creeps up
very gradually as parts wear and at first it is only heard faintly under certain conditions. Spark knock
mostly happens under high load conditions... accidentally trying to start in 3rd instead of 1st or towing
a heavy load uphill. It is easily reproduced and you will know what you did to make it knock

You may want to check your fuel pressure to see if it is dropping low. A good workshop will be able to
test the pressure for you. If the pump is getting tired or if the filter has not been changed for a long
time the pressure may be dropping under load. Even a bad batch of fuel where the octane rating is too
low can cause spark knock. If you can narrow down the circumstances when the knocking sound is
heard (high load, low load, accelerating, decelerating, cruising etc) that will help make a diagnosis.

Cheers... jondee86