ACV Noise - Need help
 

I finally got my reman installed. After priming, she fired on the first turn. Had an immediate oil leak (C clip hadn't engaged the oil cooler feed) that was easy enough to fix. All appears well except one issue. I have a strange noise coming from my ACV when I give it any throttle. Sounds just like the squeal from a slightly loose belt. It doesn't happen if I give it throttle very, very slowly but I'm talking slooooow. I'm sure it's from the area of the ACV because I can localize it listening through a peice of heater hose and when I disconnect the air pump connector, the sound is gone. Completely. The car appears to run fine in every other way. I'm sure I've done something wrong but I hate to take the UIM off without some idea of what I'm going to do next. Ideas please.

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/cant-get-rid-moo-sound-%40%25-665335/

I had the same problem and I fixed it last night. Do this mod and the noise will go away but make sure you drill the holes with very small diameters.

It's not the infamous mooo sound. It's not coming from the air return hose.

Pull the ACV off and see if the ACV internal junk is in place. I believe there is a filter and gasket which can cause noise issues if they aren't not positioned properly. Its been a LONG time since I've seen one so I can't remember exactly what's all in there. ;)

Yea, I'm pretty sure it's air squeezing past something in the ACV. I removed the ACV when I had the LIM off. It was a stupid thing to do but i wanted to check the condition of the valve that sits between the ACV and the LIM.

Damn, I hate to take that UIM off. I assume I can reuse the metal UIM to LIM gasket.

I'm almost sure it's the internal gasket. Mine made the same sound and I'd not seated the gasket properly. It is reusable and a thin film of oil will hold in place while you attach the other portion of the ACV.

Sounds like I have the same problem. Happened after the UIM was removed - though be advised in my case the ACV was not detached.

After everything was assembled, would do this weird squeal starting around 2.5K - to maybe 4K rpm max. Throttle also had to be very easy or it would go away. Was bummed at first thinking maybe it was the turbo. But after using the steathascope heater hose trick, also narrowed it to the ACV area.

Just another data point, mine is a 93 R1 with the paper like gaskets. I got in new gaskets and new check valve - hope that is it. Solenoids are a bit pricey to just buy and install on a whim. Please post what you find and I'll do likewise.

Many times it can be either the gasket or the "wagon wheel" check valve that sits in the intake manifold behind the ACV. If the wagon wheel is cocked a little and pinched, you'll get noises.

You should always use the metal gasket, the paper gasket is a joke. Pull the ACV, make sure the wagon wheel is in good shape, use a little Vaseline or something to help keep it in place, install gasket and ACV.

Dale

Ok on second thought I think I'm having the same problem too. So in other words what your saying is to fix this I'll have to take off the UIM in order to get to the ACV and that the gasket is located there?

Knee deep in removing the UIM to get to the ACV. Was reviewing info to see what else I could/should accomplish while in here and came across the following tidbit on http://www.robrobinette.com/hoses.htm Sound familiar?


Chris Davis Adds
After reassembling everything on the car I was getting full boost in both turbos including a nice transition from the primary to the secondary. The problem was between 2000 rpm and 4500 rpm I kept getting a loud squeal coming from under the intake plenum. I narrowed down the noise to the air control valve (ACV). I removed the intake plenum again but could not find anything wrong with the ACV. I finally received advice from Dave at Blackstone Performance. I told him my problem and he told me to open the ACV and check to see if the metal disc had slipped down a little while I was reinstalling the valve. I loosened the three nuts on the valve and sure enough the disc was not flush with the intake manifold (I could tell because it left an imprint in the black carbon build-up). I tried to pull the metal disc up with a screw driver but the disc kept falling back down. In order to make the disc stay in place, I had to remove the solenoid rack (again) and pull the valve completely off. Next, I put a little rubber cement around the disc (from the advice of Dave) to give the piece a little tackiness so it wouldn't fall off again. After reassembling everything, another sore back, and much frustration the car runs perfect with no annoying chirps.
I also learned in the process (from Dave) that the ACV is only active between 2000 and 4500 rpm which is what clued him in to the problem. I can also remove the intake plenum in about 15 minutes but I hope to never have to remove it again. Anyway, I just thought you might want to mention something about the ACV disc to save someone else the headache of having to remove the solenoid rack twice. Once, as you know, is plenty.
Chris Davis

Sounds like a lot more than I expected. Does anyone have a photo of this ACV with the UIM off? I've never taken mine off and I can see it in the vaccum hose diagram but even if I did have my UIM I'm sure a photo will still help.

I pulled the puck out tonight and it does appear to have had some leakage given the carbon residue. I'm not reinstalling until I get back from vacation. What a crappy design.

Do you mind taking a few photos?

Pic's

Well I got home last night from the family summer vacation and this morning I spent an hour installing the UIM. Started 'er up and the squeal is gone. Yahooooo!!! Problem solved. My 7 runs like a champ.

The LIM has a very shallow chamfer that the valve/puck sits in. I guess I hadn't quite got it seated correctly. I used just a tiny spot of Right Stuff to hold the puck in place while I installed the ACV. Jeeez, what a PITA to fix.

Someone should add this issue to the FAQ. Much thanks to ColdFeet, Dale. Majik and others who responded to my thread with the right advice.

My purchased new, chaste white, base FD is back on the road with a newly installed Mazda reman. Hope I can put another 100K miles on her.

Just to close this for those that follow....

My noise kept coming back like the energizer bunny. People can call it a Moo, but sure sounded like bearings going out to me. I replaced the valve twice and even the whole ACV with another used one - still had the noise. :wallbash:

Thanks to this forum even if by accident - I finally found the problem. I have the M2 air intake. Someone was selling theirs and happen to have a pic showing the back of it and I noticed that the air pump relief hose connector had a restricter in it. Hmmm. I go out and check and sure enough, somehow my restricter had gotten punched out. All this time.... sigh. On a positive note, I can now pull and replace the UIM in under 20 mins :icon_tup:

Moral of the story => You MUST have airflow restriction somewhere in the ACV relief line.