Screaming, Squealing noise at idle.

[gotglasses]

I got a shock this AM getting off highway, car was fine at speed . as soon as I take my foot off accelerator the car squeals in an ear shattering squeal. I checked clutch, brakes and fuel pump. It seems to be coming from inside the middle of the car. The only part I can think of is the Altitude compensator, but that never acted up before and must cost a fortune. How do I fix this cheaply?

[Roadtrip]

What year and model is your car? Have you checked for an alternator that's loose in it's mountings. With the engine off, grab it and try and shake it. It won't be obvious by just looking at it.

[ossodiseppia]

Never heard of one of them making a noise. But if you need one, I will scrounge one up for you.

[gotglasses]

This is an 86 Quad Spider. the noise goes away when I blip the engine or accelerate, foot off the gas and noise starts. eery. Must be high vacuum related. sounds like brake squeal but it is not. Not coming from engine, this leaves me with the fuel pump - which seems at it's normal loud self. I have a fuel odor in the car , wonder if it could be from the carbon cannister? This is a part that I have never found, but am told it is in the fender.

[Roadtrip]

Does sound like vacuum. Try disconnecting the line from the fuel vapor recovery system up in the engine and see if it goes away.

[geh458]

Quote:

Originally Posted by ossodiseppia Never heard of one of them making a noise. ....

[papajam]

I've no personal experience with this but I've read that a vacuum sensor located behind the right seat by the ECU can emit this squealing sound.

[gotglasses]

Pulled the cover off the rear P/S , Altitude device squealing at idle. Took it off ( all nice and shiny, like new) and found a nasty, rusty piece that I had in my spare parts bucket (from another project car - never throw away the junk in the trunk ). Under the dirt it had the same part # - and it does not squeal after installing it.

Another amazing thing - my car ( and other Alfa in the past ) would not turn on the alternator after starting until I raced the engine slightly, the charge light stayed lit while it warmed up. Now, with this other altitude compensator , it immediately extinguishes the charge light when it starts!

This must have been a significant vacuum leak , wonder if it contributed to my recent emissions headache?

Thanks for the feedback guys!

[gotglasses]

OOps - it is a vacuum sensor, not the altitude compensator which connects to the injection computer. This plugs into the ignition computer. I guess it acts like a vacuum advance on an ordinary distributor ignition. Anyway, it is quiet now and got rid of a vacuum leak by replacing the part. Are these still available as a new part?

[Bill]

Quote:

Originally Posted by gotglasses Another amazing thing - my car ( and other Alfa in the past ) would not turn on the alternator after starting until I raced the engine slightly, the charge light stayed lit while it warmed up.

[gotglasses]

I'd say a quirk since all 4 of my cars have done that, maybe a ground wire to the Alternator would help? Car needs a little surge on start up to turn on the alternator. My vacuum issue helped this but it is still there when cold.

[papajam]

Way to go, gotglasses! Just send GTV parts. J/K

I suspect that the alt light going out now at startup is because of a slight startup rpm change that has occured as a result of the vacuum leak being repaired. I base this on knowing that one can change the rpm at which the alt light goes out (and when the alt starts to charge the battery) by changing the bulbs wattage.

[gotglasses]

changing bulbs? getoutahere!! This I have to try.

I'm starting a new thread on my radio/ cigar lighter issues.

BTW - Ebay has a vacuum sensor for sale by the DeNoya Res. - They are calling it an Altitude compensator TOO!