Weird whistle sound - Mk1 16V K-Jet

[HuH]

Yesterday I was driving on the motorway in fifth gear, and after cruising with part throttle for a little while I noticed a strange whistling sound. It went away and reappeared a couple of times, only in fifth and only after a kilometre or so of part throttle cruising around 80-90km/h.

I filmed a very brief video with my phone so you could hear the sound. You can watch it here: Mk1 16V K-Jet Air Leak? - YouTube

Could it be a slight air leak causing the whistle? Volume was related directly to throttle position, and the pitch increased with the engine revs.

I'm driving the car down to Canberra for GAD in a couple of weeks so I'm hoping to get this bug ironed out and avoid three hours of whistling down the highway!

Thanks.

[Blue Flog]

Check the idle adjustment screw on the back of the throttle body. I have had 2 work themselves out due worn o-rings on the valve.
Darcy

[HuH]

Good idea. I'll take a look at that, but surely that would cause the idle to go erratic? The car still runs and idles perfectly.

[Blue Flog]

I only had a high idle. The other source could be the air hose to the cold start injector.

[HuH]

This has been really hard to diagnose. Someone else has suggested that it could be the alternator. Apparently it's not charging particularly well so that sounds plausible. Does anyone have any input on that? Ever had a whistling alternator?

[ryana89]

The alternator on my MK2 'whistles' or whines under heavy load (all lights on), but not that loudly.
Alternators can load up if you've got bad groundings, dying battery or with heavy loads.

Do you know when the alternator was last reconditioned?