I'm getting this high pitched metal on metal sound when I rev my new engine. It starts around 1800 RPM and only is audible when accelerating. It sounds like it's coming from underneath the UIM so I took the ACV out and I'm going to test it today. It is definitely not the airpump because I have tried 3 different ones and I still get the same sound. If I unplug the airpump, rev up the engine, there is no sound. It almost sounds as if the ACV is fluttering inside and the noise gets louder as the RPM's climb and the airpump puts more pressure on it. I have not driven about 3000 rpm yet since I've only got a couple miles on the reman.

Anybody else's ACV go bad? If so what were the symptoms.

 

I am very interested in this too.

I developed a simular sound (as you described) before winter. I Also checked my air pump. Which was fine. I am planning to pull the UIM to check my ACV now that I am driving again. I first thought it may be the 2 Vac lines above the ACV. After my Vac hose job I might have cut them a little short so, they might be pinched?. When I rev it over 3000 it goes away.

Does your sound start right way from a cold start? My sound starts (sometimes) when car is warmed up and after a short drive.

I have read many have removed the ACV but I would like to keep mine for now. Hope someone can help us both.

 

my vaccuum lines were not pinched. the car makes a short squeak noise everytime i start it up. it doesn't make any weird noises at normal idle, 800 rpm. it makes the noises the same whether the temperature is cold or hot. i am going to buy a vaccuum tester right now and pick up another acv tonight so we will see. this thing is driving me crazy because i can't break in the car yet....

 

this is an update to my problem. i found the problem. it was the circular 1" check valve in between the LIM and ACV. it was not centered correctly and had fallen down about 2-3mm from where it was supposed to be. i suppose it just fell down when i was installing it. i reinstalled it correctly and the problem is gone. the high pitched metal fluttering sound is gone and was that little check valve was what was fluttering around. two clues to this were the carbon on the inside part of the check valve was squished into an elliptical pattern versus circle pattern. there was also a perfectly circular mark on the acv from squeezing the check valve in the centered position, then there was a small black mark on one corner where it had fallen down and been squeezed when it was incorrectly installed. hopefully this info. will help someone in the future. this was a tough one. on a lighter note i finally started breaking in my new reman.....125 miles today! woohoo!

 

Great to hear you found the problem. I have not had time to take my UIM off, maybe tomarrow? Thanks for the information, hopefully mine will be solved too.

 

my car drove perfectly normal with a bad ACV.... I was just a gross polluter