JormaK

My 964 started to "knock" when warm few days ago. Fuel should be OK.
When cold, engine sound normal, maybe idle is "sailing" a bit more than usually. But when warm, idle moves sometimes more. Where i sould try to find problem?

Knocking (detonating?, hope I use right word..) sounds like to come only other's side cylinders. -Not all the time, but when driving like bigger gear and lower rpm's..

I'm thinking air leaks somewhere? Anything else I should check up?

Spark plugs are old, and gonna replace them soon (can old/broken plug cause detonating/knocking?) -And what "loose" plug can do?

Becouse detonating is extremely dangerous, ofcourse I not driving now And gonna fix it asap

Rocket Rob

Check your distributor belt. When my belt broke, the engine ran but was pinging (detonating). Its an easy thing to check, just remove the secondary distributor cap and see if the shaft rotates freely. It shouldn't. If it is broken, disconnect the secondary distributor's controller. That will make it safe to drive until you have time to fix it properly.

C4inLA

What and where is the secondary distributor controller?

crg53

Controller = igniter. It's located right below the coils.

Hem

does it sound like this? I made this video when I was trying to figure out some noises and it was a broken dizzy belt.

JormaK

Distributor belt seems to be OK. Next trying to find vacuum leak...

Rocket Rob

Just to be safe, I would still try disconnecting the secondary distributor and run the engine.

Steve Weiner-Rennsport Systems

Make sure all of your plug & coil connectors are properly seated.

Goughary

As long as we are chiming in with potential issues... I'll share some of my experience too..

I had a shop once swap my distributer caps. They did two strange things. First they installed one backward. There is a tab that needs to seat in a slot or it goes on crooked. That caused me misfire issues.

Then, same shop didn't screw down the screws on a dist cap well, and it came loose. That caused issues.

Then, my original wires has been on the car for the first 75k miles. I found that a few of the boots had unscrewed themselves but seemed to be connected. It's a good idea to check each of your wires with a multimeter. For the above reason and because inside each boot is a resister that can go bad. Put a multi meter I each wire and see that each reads close to 3 ohm. Or if your wires are just very old, they may need to be replaced as they may be leaking and arching...

So many gremlins to chase down...you'll figure it out pretty quickly. Whatever it is will be immediately apparent when you find it.

Oh. And beru distributer caps suck. The posts tend to break out and that also is no good. Bosch caps are much more reliable.

Rabs

+1 on checking secondary distributor. I had the belt break and it made a terrible noise. Please see this link

http://i1168.photobucket.com/albums/r497/rabsrussell/Porsche%20964/B5B0AC2C-A8EA-4386-9167-F6C6076ADE1E_zps3r1vkifn.mp4
It's the lower distributor and if you remove cap it's obvious as the rotor will spin freely if belt is broken.

-nick

Do you idle at 1100rpm when warm? If so, you've got an aftermarket Autothority chip, which is why your pinging.