Odd knocking noise under initial load

[Don in VT]

Hi,

Now that I have the exhaust calmed down a bit with the addition of the X pipe I have a new noise to track down the cause of. When I start the car the cam chains make their 1 to 2 second rattle. When I press on the gas a noise appears that almost sounds like the older diesel motors. It is a mild knock. It only is there under initial load and is gone by 800 to 1000 rpm. Above 1K rpm the motor is smooth and quiet. I am sure that this motor has been run hard but it does not smoke or make any unusual noises above 1K rpm. Could the knock be rods, mains, wrist pins ? I did do the search .

Any ideas

Don

[Kb7tif]

internal engine wear

[tomtom72]

Do you still have the duel mass flywheel? I have been told that it can make some knocking noise at low rpms once the springs start to loose their tension.


Tom

[Kevin]

could be tip in knock, could be something else. almost impossible to diagnose over the internet

[A26B]

Don,
Rod knock can be checked by the following procedure.

1. Emergencey brake set
2. Engine running
3. Hold rpm @ your knock range
4. slowly release clutch to point load is detected on engine

If knock noise ceases, then most likely a rod bearing is worn & clearance is excessive. Rod knock will still be present at all rpm's, most noticable with no load on the engine.

If knock continues, then rod bearings are not likely to be the source of the knock.

A worn, dual mass flywheel is generally mis-diagnosed as rod knock. The few I have experience with, only knock at low rpm. Your description

It only is there under initial load and is gone by 800 to 1000 rpm. Above 1K rpm the motor is smooth and quiet.

describes this condition perfectly. There is nothing terminal about the condition, just an embarassing noise at idle.

Sometimes new plugs, gapped at 0.045" will help, if all other elements are good, i.e. coils, wires, injectors, etc.