Davies

I posted a few weeks back that I had what appears to be engine knocking at
around 4000 RPMs. Despite the excellent (and much appreciated) advice, it's
still doing it!!

So far the distributors/belts have been checked, fuel injection flow pattern/rates
checked, coils, ECU, new Bosch plugs in an otherwise perfectly running engine.
No power problems right up to redline, just a very slight metallic chatter from the motor
at 4000 rpm (and not beyond that).

What am I missing?? Any further suggestions???

Help!!

chris walrod

even though at 4k rpm you should have great oil pressure, maybe a lifter (rocker) is going soft on you?

Sounds as though this may be mechanical, not elcetronic...

TrackJunke

Could it be something as simple as a heat shield or something like that rattling at that certain RPM for some reason. Just an idea.

Robin 993DX

Have you done the varioram function test yet?

The testing procedure is listed inside the shop manual under the "engine" volume.

Basically you will need to disconnect the vacuum hose that is connected to the bottom of the solenoid that controls the flap to regulate the fresh/engine air flap located on the left side of the engine in front of the heater ducts. Plug the vacuum line up to prevent any vacuum leaks.

(BTW, the engine must be warmed up already to do this test)

Start the engine and hold it at 2500 RPM for 10 seconds.

Turn off the ignition

Have someone else turn the ignition to ON positon (One click before the starter) as you keep you eyes on the varioram diaphram on the both sides of the varioram intake runners.

You should see them move.

Davies

Thanks guys.
TrackJunke: I was hoping it was that when I first heard it..Though unfortunately
I cant find anything externally that will make the noise...

Robin: I'll check that out. If the varioram doesnt move...would that cause knocking?

Chris: I HOPE it's not that....