Help identifying engine ticking or clicking noise

[SpawnyWhippet]

When my engine is running and warmed up, every few secs or so there is a fairly loud ticking or clicking noise. I am tring to identify this, from some preliminary googling it could be a head stud bolt that has come off inside the valve cover. I have uploaded a video of this and would greatly appreciate some assistance identifying the cause of the noise.

[Chuck Miller]

Spawny,

I would ask if the idle changes, even minutely, when you hear the tick? ... I think I heard a slight momentary change...

If so I would ask when the last (or if ever) you had your throttle bodies rebuilt?

As a test I would 'play' with the air adjusting screws, one at a time, and see if there is any change...

I had a similar ticking sound just before I had my tb's rebuilt... the ticking was at idle when the compression was hitting the badly worn throttle plates, shafts, and bushings causing an intermittent tick/w an ever so slight hiccup in the idle when it occurred ...

It's worth a try..........

[SpawnyWhippet]

The MFI was rebuilt by Pacific Fuel Injection about 6 months ago, so I hope that is OK. I'll fire her up again today and see if I can detect the idle changing when the tick occurs. The car is running rich and the plugs are sooty, so it probably needs some tweaking anyway. Can anyone recommend a decent mechanic in the Bay area who could look at this?

[edmayo]

There are two different subjects here, Chuck is referring to the throttle bodies but you are confusing them with the MFI pump rebuilt by Gus,,,,,two different MFI parts, Gus does the pumps, not the throttle bodies. Just trying avoid confusion of terms here.

[kentf14]

Not that I know ANYTHING close to Ed or Chuck.... but
I can't hear a "regular" ticking. I hear an irregular tick/pop
Is the sound you hear metallic? You likely have thought of the following, but..
Possible sources that I'd think of
throttle bodies
valves (when is the last time they were adjusted? Loose valves will tick when warm)
timing chain slap
Rod knock (low oil pressure = knocking sound)

[SpawnyWhippet]

I will try to get someone to look at the throttle bodies. I am reading the MFI section of Wayne Dempsey's 'Rebuild your 911 motor' book now and it certainly seems be beyond my abilities.

The ticking is very metallic and not regular, its on average every 5 secs, but could happen twice in a second or not for 10 secs. It doesn't do it when the engine is cold. I'll try and localize the sound with a stethoscope.

[edmayo]

I'm with Chuck in that popping in the intake stacks can sound 'metallic'. There can be a number of causes from worn throttle plates to improper mixture settings and or idle speed RPM. If that's what you're hearing just know that its not hurting anything, but that's not to say that you shouldn't pursue trying to solve the problem. To some degree we are spoiled by the refinements of modern cars and their computer controlled everything (albeit at astronomical replacement costs when they go bad) that we forget that our favorite cars are comparative stone age technology and these quirks are part of living with them.

[SpawnyWhippet]

Thanks for the earlier input. I have the throttle bodies, stacks and MFI pump assembly on the bench now, as the engine is removed from the car and having a top end rebuild for the valve issues I mentioned in another thread. I noticed that some of the connecting rods for the throttle bodies are not tightened properly and need to be adjusted and tightened with the locking nuts.

Can anyone recommend a throttle body rebuild DIY thread or tutorial, and where to buy a rebuild kit?
How can I best check for overall condition and wear, eg on the butterfly valve bearings?

I am determined to try to get my head around MFI and the overall fuel delivery system for this car. I've bought a LM1 exhaust gas analyzer and am looking for the Porsche protractor tools (P228B/C) to try and set this lot up.

There were a number of random disconnected hoses around the engine when I removed it, so I am hoping that the main cause of rich running was that the thermostat heater hose from the SSI was not connected to the MFI.

I also found a couple of as-yet unidentified hoses that were disconnected and laying behind the MFI pump. These route down into the bulkhead by the transmission shifting tunnel and run forward somewhere, but I cannot find out where. They are NOT the AC hoses, as they are 100% identified and run elsewhere.

[edmayo]

Okay, first, if the hot air hose was not connected to the thermostat it will run REAL ungodly rich!!(major emphasis here) The other two hoses you mention are for the charcoal cannister system. If you can feel sideways play in the throttle shafts they are worn out,,,,no need to measure. When you say the connecting links are loose do you mean the locknuts came loose and the threaded rod was unwinding from the socket ends? There is no tutorial for DIY of the throttle bodies as that recquires expensive machine work, such as milling equipment, not likely to be found in the average garage. From your description so far I'm amazed the engine even ran.

[Chris E]

Couldn't it simply be a "lean pop" in a particular cyl when reaching working temp? (the metallic sound beeing some worn component trickled by the pop) Are all 6 plugs running rich? Try a new set and see if all cylinders are equally sooted? I mean, since it doesn't do it at startup...? (When it runs richer?)