Rob in Oz

I've had my '93 964 C2 for 5 months now, and it's always had this annoying "zizzing" noise at idle, which the PO was unable to get his tech to locate and fix. Today, after some disassembly to fix another problem (popped manifold connectors after 130km/h backwards on grass at track!) I found the sucker. It's the steel pin arrowed in the attached pic, in the lower part of the connector between the inlet manifolds. If I touch it while the engine is running, the noise stops. There is also a strong high frequency vibration going through the pin. PET (as far as I can see) doesn't give much detail on this, but I suspect that it's a pivot shaft for a manifold butterfly valve. Is this a common thing, and what is the best way to fix it?

TIA

Rob

MisterRisky

I would guess you are right as to what it is, but I don't think this is terribly common. Can you put a washer or two behind that E clip on the end of the shaft? That might make it all more snug and help with your vibration. Usually these types of set ups where you have a metal shaft, metal E clip and a plastic housing would have a washer behind the clip to keep if from rubbing the plastic housing. It does not appear that there is one on there. After I get some daylight here I will take a peak at mine (if I can find it on my car )

Geoffrey

That is the pivot shaft for the resonance flap in the manifold. They wear out and begin to leak. If you smoke test the manifolds, I bet you'll find yours is leaking and needs to be replaced.

drola

on the opposite side of that e-clip there is a lever which goes hooked up to a vacuum actuator. does anyone know what that lever goes hooked up to?
when i tore my motor down i realized this but i really don't remember having disconnected it. but it does look like it was connected to something.

Rob in Oz

Guys

Thanks for your replies - most illuminating. As my C2 is quite low mileage (115,000km / 70,000mi) I wouldn't expect a lot of wear in the shaft. My guess is that the actuator on the back has been dislodged (or not put back on) and is allowing some freedom of movement. So - I'll have to pull the manifold to check it out. BTW, the replacement bit is listed at ~$2400 on Pelican, so I won't be rushing out to buy one any time soon!

Thanks again

Rob
1993 C2

1pcarnut

When I read your post, I thought this was a question concerning Viagra.

parsecnc4