Help me – my car is making a horrible wining sound!

[lpraun]

OK – This is the situation. The car starts fine with full choke and warms up nicely – choke gradually off and after 5 minutes it idles at about 700 rpm with no choke. After a good drive, when it returns to idle it makes a horrible wining sound and will stall or run at very low rpm.

If the engine stops and I try to start it again it is very difficult to start. Choke does not help and if it starts it runs at very low rpm – and eventually stalls.

I have made a video of the engine making the sound. I am the one who rev the engine in order for it not to stall – as it does in the end of the video.

It’s a 73 car with 3-screw round top SU carbs. With all 73 emission control systems still installed.

Does anybody have any idea of what is wrong and what I can do to fix it?

[260zCaliCar]

My diagnostic skill is nothing like everyone elses, but if I were to guess (without listening to the video) I would venture that your over heating and the fan clutch is kicking in. Someone may want to make a better suggestion, but that's my guess. FWIW

[manny1973]

bad fan clutch or water pump??

[lpraun]

The fan clutch is good, and I installed a new water pump a couple of months ago. It sounds like the sounds comes from somewhere around the carburettors and the heap of emission control tubes. The car is not overheating, and I just changed oil and the level and pressure is good.

My big worry is if somehow there is a problem with the lubrication of the camshaft or any other mechanical component, resulting in excessive wear or failure.

[ChrisZ]

LP if you take off the 710 then you should be able to see if your cam get's oiled, try to take a piece of hose and use it to listen for the sound, see if you can get any closere to it, i'm in my summer house right now and you are welcome to look by and i will be home on Friday before leaving for Italy, so if you like to borrow some smog stuff, it have to be then.

Let me know.

[Curtis240Z]

It sounds like your air pump is going bad. The noise I hear from your video clip sounds like a small fog horn. Try and remove the belt for the air pump and see if the noise and your performance gets better.

Edited July 27, 2009 by Curtis240Z

[FastWoman]

It doesn't sound like a bad bearing to me, as it only has one constant pitch that doesn't vary with engine speed. I'm speculating that it has no relation at all to lubrication. It sounds like some sort of air valve to me -- one of the emissions valves, perhaps -- or maybe a vacuum control. Anything making that loud a noise should probably vibrate pretty well. I'd start feeling around for vibrations in the different parts that have diaphragms.

[Diseazd]

I 2nd the bad air pump bearing. Chop the belt and try that.

[conedodger]

Dude! Where is your cat???

Seriously, lose the air pump.

[bobc]

Sounds like an air leak to me. Probably a small vacuum leak that's causing the rough idle and stalling as the car runs lean. When the car is cold it's probably not bad. As the engine warms up and expands, the leak opens and hence the sound. As you increase the RPM's the vacuum increases, but the tone changes because you have changed the volume of air going through the leak. Kind of like the difference between whistling and just blowing air through your lips.

Could be one of the emission control valves too. Not a bad suggestion.

The best thing is to try to start isolating where the sound is coming from. Try using a long handle screw driver against your ear or a piece of hose. Once you get in the general area, you should be able to start isolating the sound until you find where the sound is coming from.

For my two cents, it doesn't sound or act like a bearing.

Bob

Edited July 29, 2009 by bobc

[Walter Moore]

I agree with BOBC. This is a common problem on some cars with throttle body FI. They will get a small vacuum leak in the gasket under the throttle body and make almost the same sound, with the same inability to idle.

The screwdriver trick usually works. Normally you will be looking for a leak somewhere on the intake manifold. Goodness knows there are enough places where it could leak.

[lpraun]

Okay guys – did what You sad, warmed up the engine and when I returned home it had a hint if the sound, when I manipulated the throttle. I tried to disconnect different hoses to the emission control systems with no result. I then took of the air cleaner box, and then the sound became much louder and I was able to locate the sound to the idle compensator positioned on the air box back plate. I disconnected the little hose hidden away inside the jungle of other hoses in order to see if I was right – and I was:)

It’s nice to know nothing serious is wrong with the engine – now only my pride is subjected to excessive wear when I idle at a stoplight:embarrass:

Thank You very much for the valued input.

The next question is then how do I fix this or how do I test the idle compensator to se if it works properly – the sound from the idle compositor might still just be a symptom of something else wrong!