Alfa Romeo Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
247 Posts
Discussion Starter #1
Afternoon all, this issue is really starting to get on my nerves now, basically if I try and accelerate over 50% throttle, I get this annoying whistling coming from behind the glovebox (which changes tone as soon as the throttle position changes). For the life of me, I cannot find anything wrong. The top turbo hose is new, the bottom is fine, I haven't checked the intercooler yet though. Only does it with load on engine, I have smoke as well, and if I try and maintain a fixed throttle position I get what feels like a misfire!

Any ideas?
 

·
Registered
Joined
·
247 Posts
Discussion Starter #3
Ha Ha cheers, I'm aware that there is a vacuum reservoir behind the engine somewhere around the glovebox area, I'm wondering if I have a split hose around this area, as it's definitely coming from behind the dashboard, passenger side.
 

·
Registered
Joined
·
796 Posts
The miss-fire and smoke suggest excessive EGR, perhaps the valve has stuck open. I don't know that it would whistle though, unless it is also leaking – do you smell fumes inside? Anyhow, the valve is relatively easy to clean, or try a blanking plate. They are readily available.
 

·
Registered
Joined
·
2,270 Posts
Top turbo hose fits the bill given the location of the sound. Vacuum leak wouldn't be audible in car as you accelerate.
 

·
Registered
Joined
·
247 Posts
Discussion Starter #6
The egr has been cleaned and is working correctly and fitted with the modified semi-blanking plate, it may not even be vacuum, but something is definitely leaking when it shouldn't be! I cannot replicate the noise when the car is at a standstill, only when driving! The top hose is a relatively new silicone hose, with no noticeable splits.
 

·
Registered
Joined
·
796 Posts
They are small throttle plates in the inlet manifold that close off one of the two inlet ports to each cylinder at low revs. This increases the air speed in the other port and so the swirl in the cylinder which improves the combustion efficiency. Unfortunately they tend to fall off and can damage injectors/valves etc. If your car has them this is one possible cause of the miss-fire and smoke but I'm lucky, mine never had them so I'm not up on the details of which cars had what fitted. A search will find many threads on the subject....
 

·
Registered
Joined
·
247 Posts
Discussion Starter #10
I have found out that the car, although a late 2005 model, has the CF3 engine, so reading up on that I'm guessing that it doesn't have them. It has a metal inlet manifold as well.

I've noticed as well lately that as it starts to make this whistling noise, as soon as I let my foot off the throttle it makes a slight flutter noise, a bit like a dump valve!

It was quite funny to start with, but now the novelty has worn off. I'm convinced that it's not the top turbo hose, it is silicone and there are some wear marks on it, I've had the hose off and had a good look at it, but can't see any splits in it at all!
 

·
Registered
Joined
·
796 Posts
Is the throttle in the (driver's) left hand end of the inlet manifold working properly? It should be spring loaded open, and only close at key-off; it's there to provide a judder free engine stop. Is the vacuum capsule connected to it, and does it snap shut at key-off, and then open up to 20 seconds later? If so it's probably OK.

Don't discount the EGR valve just because you have cleaned it. Mine can start sticking again within a few hundred miles of a clean; I think others find the same(?) I bought a blanking plate just for diagnosing this sort of problem. It's the easiest way of knowing the (insert expletive of choice) thing is sealed.

I'm not sure about the fluttering noise; the only time mine has made that noise significantly was when I deliberately stopped the engine while on boost by manually closing the throttle. Hence my question about yours.
 

·
Registered
Joined
·
247 Posts
Discussion Starter #12
Is the throttle in the (driver's) left hand end of the inlet manifold working properly? It should be spring loaded open, and only close at key-off; it's there to provide a judder free engine stop. Is the vacuum capsule connected to it, and does it snap shut at key-off, and then open up to 20 seconds later? If so it's probably OK.

Don't discount the EGR valve just because you have cleaned it. Mine can start sticking again within a few hundred miles of a clean; I think others find the same(?) I bought a blanking plate just for diagnosing this sort of problem. It's the easiest way of knowing the (insert expletive of choice) thing is sealed.

I'm not sure about the fluttering noise; the only time mine has made that noise significantly was when I deliberately stopped the engine while on boost by manually closing the throttle. Hence my question about yours.
Thanks again for your help, I'll have a look at this as soon as I can and see what I can find! I'll feedback how I get on!
 

·
Registered
Joined
·
1,134 Posts
My old alfa 156 had a real loud whistle and had it for 5 years with no problems, it was a slightly chipped rotor in the turbo but as the vanes needed replacing anyway as they were sticking I never bothered with it and in the end I decided to sell the car anyway as it had a couple of other serious issues, and don't worry about a bit of scuffing on the top hose as mine was silicone as well and rubbed but it was only superficial :)
 

·
Registered
Joined
·
247 Posts
Discussion Starter #14
Just thought I'd update and say that this has been fixed now. I noticed that there was quite a bit of oil on the lower part of the turbo hose (where it joins the top of the intercooler). I took the hose off completely, cleaned it, refitted and now there is no irritating whistling noise! It seems like that the hose had partially slipped off the top of the intercooler.

Also took the opportunity to clean the MAP sensor in the inlet manifold, it was absolutely caked in soot, so blasted it with some electrical cleaner, and now a combination of the two have made the car go spot on! I'd highly recommend doing this, it only takes 5 mins!

Thanks for all your help.
 
1 - 14 of 14 Posts
Top