This noise with my EL GLi has been happening for the last three or so weeks. It is hard to describe, but the closest thing I can think of is if you've ever folded a leaf in half and blown through it - it's a high pitched, almost grainy whistling sound.

But it only happens
- In the first 5-10 minutes of driving when cold, after leaving the car for a few hours
- Between around 1500 and 2750rpm
- Only under throttle, the split second you take your foot off it's gone

After 5-10 minutes it disappears, which makes it hard to find out exactly what it is. Initially I thought it was an intake noise, so cleaned out all the crap from the throttle body, that didn't do anything. Then this morning when it was happening, it almost sounded like some sort of exhaust leak. This could be the case, as I'm pretty sure I've got a dodgy cat anyway (chugging exhaust sound, and economy is consistently up around the 18L/100km mark).

Any ideas?

18L/100km? You must be made of money!

O2 sensor, blocked cat, stuffed MAP sensor and/or vacuum leak can cause such poor economy.

Anyways, with the squeal, does the pitch change when you accelerate? If so, it might just be the idler pulley. Also check your power steering pump...make sure the fluids are topped up...it can make some sort of squealing noise if too low.

Haha! Not anymore I'm not! Already 3 weeks overdue on rego, and have to save for schoolies!


Changed the O2 sensor already, made zero difference. She's done 160000km and I wasn't sure on when it had been done, so thought may as well. Blocked cat is my next guess. Would a MAP sensor make THAT much of a difference?


Yeah the pitch increases with acceleration, up to about the 2750rpm mark. But it not really a squealing noise, which is why I am steering away from anything to do with the belts. Also, I changed the serp belt and power steering fluid about 2000kms ago. It's like a whistling, which makes me think air or exhaust. Also, because it goes away once it has had a chance to warm up, then comes back like clockwork when cold, I'm not sure it would be the idler pulley.

When I first noticed, I thought it was coming from front left (eg. why I thought it was intake/throttle body), but the more I pay attention, the more it sounds like its coming more centre/rear left

MAP sensor leaking vacuum can cause you to lose power in a sense. Actually any vacuum for that matter. The engine has to compensate for the vacuum and you put your foot down to compensate for the power taken from the vacuum.

Anyways have a look around for any possible vacuum leaks. When the engine gets warm, metal expands and this may actually seal it up again or something. Check intake and exhaust bolts, make sure they aren't loose (don't tighten up too much if they are loose, you may strip the thread in the alloy head) and maybe get the exhaust checked for leaks.

Also, pay your rego please...if you hit someone and hurt them, you are not covered for their medical bills and quite frankly, I don't like it. Priorities!

Believe me, I can't wait for payday this week so that I can actually do that! Sucks having to catch the bus everytime I don't need the space of the wagon.

Okay so vac leak seems on the money. Might take it in to our bloke after school so he can have a look at it as well. Fingers crossed it's as simple as tightening a few bolts

Okay, so here's what the doctor says:

Regarding the fuel issue, he didn't fidn anything wrong with the cat, and he thinks that the injectors may be to blame. I forgot to mention that before I bought the car in July, the owner had left it sitting for quite a while. The wax buildup in the injectors might be making the engine work much harder than it needs to, which I haven't really noticed, but mind you it's been this way since I've been driving it. He also did an emissions test, and said it was actually running a little lean at idle, which adds to the engine overworking argument. Also said to check the thermostat & radiator cap, as it doesn't seem to be holding pressure in the cooling system.

Regarding the noise, he checked for vacuum leaks in the engine bay and couldn't see any. Whether this was because the engine was already warm (it only makes the noise when cold) I'm not sure, but I'll do another check in the morning. He did note that the mid exhaust was a bit rooted, which was causing the chugging exhaust, the rattles, and maybe the noise. I was planning on getting a cat back and start my modding adventure when school is done in a month or two, so I may as well kill two stones with one bird there.


One last thing, if anyone is in need of a decent mechanic in the eastern suburbs of Melbourne, I go to K&C Auto in Blackburn. Ask for Karl. He's a top bloke and definitely knows his s**t when it comes to his Fords (and motorbikes). I thought he deserved a bit of a shoutout.