shurton

My mechanic just told me that my low idle is caused by a defective Air Control Valve. Anyone know where to get one? Mazdatrix has them for ~$460, but I'm hoping to get one for less.

J-Rat

iTrader: (2)

How on earth does an ACV cause a low idle??!?!?!?!!

You need a new mechanic, like YESTERDAY.

shurton

Here are my exact symptoms:

Symptoms:
Car idles at about 500 RPM.
Idle can not be increased with idle speed screw.
Car frequently dies when AC is on.
Disconnecting BAC valve connector (as per shop manual) does not change idle.
Extreme hot starting problems.

Does not appear to be a vacuum problem.

Why wouldn't this be the ACV? I'm not a mechanic, I'm just asking.

Thanks...

shurton

Sorry I got my facts mixed up.
He said the low idle is caused by a split in the hose that connects the MAF to the turbo inlet.

I'm failing emmissions testing, and he said that was because of the ACV.

Does that sound right?

J-Rat

iTrader: (2)

Yes, that sounds more correct. But there is a way around it... You can trick the ACV into pumping air to the cats at all times in order to pass emissions. There is a thread COMPLETE WITH PICS! somewhere here...

J-Rat

iTrader: (2)

https://www.rx7club.com/showthread.p...=Emissions+ACV

shurton

thanx, I'll check it out.

ddub

I still failed when doing that =|

And I even leaned my s-afc out to -19 at 500 rpm, 1000, 1500, 2000, 2500, 3000 for the idle/cruise test

J-Rat

iTrader: (2)

Then your cat is totally trashed... Run alcohol...

ddub

Brand new Bonez hi-flow cat


I had a better idea anyways, I'm getting a P.O. box in a county with no emissions, problem solved

Aaron Cake

iTrader: (1)

Just for the record, the ACV could easily cause a low idle. During decel the ACV supplies air from the air pump to the rear rotor. This helps combat afterburn. If that valve is stuck, the rear rotor will run lean all the time....

Just an afterthought: I have just finished cutting apart an S4 NA lower intake, so I have all the various air passages fresh in my head. The intake is mostly empty space, with the bottom part taken up amost completely by the "port air" passanges (blows fresh air into the exhaust ports at various RPM ranges).

J-Rat

iTrader: (2)

So how is it that my car runs the same with or without the ACV? IF anything it would be a malfunctioning solenoid, not the ACV.

NZConvertible

That just means there's nothing wrong with the ACV. When Aaron said, "If that valve is stuck...", he meant stuck open. Normally it's closed, and is opened by vacuum under decel.

J-Rat

iTrader: (2)

Ahhh... One of those things.. You and Aaron ganging up on me?!?...

HAILERS

If one suspects a leaking acv, do this. Buy a can of STARTER FLUID. Take the airpump feed hose off the air filter.

With the car idling (fully warmed up car first), spray the starter fluid in the airpumps intake hose.

RESULT: The idle should not chang a whit. If it does change a whit....then the anti-afterburn poppet is not seating properly and allowing airpum air to leak into the intake. It should not leak air into the intake at idle.

Fix: remove and replace the acv. OR if your cheap, take the acv off and plug the hole that feeds b/t the acv anti-afterburn valve output and the intake manifold. Let the RTV set for a couple of hours and then return the acv to service.

Rex4Life

Hailers, could you please explain this? I'm trying to figure out why my vacuum is low. I don't see any way the ACV sends air to the intake side of the rotors. Yea I know it is all housed on the intake manifold, but the passages all go to the tiny exhaust ports below the main intakes on the block. I have an S4 but I think the S5 is the same.

Thanks,

Scott

NZConvertible

Go look at the schematic of the ACV in the FSM. You'll see it clear as day. There's a valve in there that is pulled open by manifold vacuum, and allows air from the air pump to flow into the manifold via a seperate passage.

HAILERS

Maybe this jpg will get thru all the obstacles this site has put in place to keep me from posting jpgs (I'm sure this site conspires against me posting jpgs )

Ignore the red dots and lines, they were put there for another thread/post. It's the AAV at the top of the acv that causes the INTAKE to get air. But only during deceleration when it was brand spanking new. Now that its got some years under its belt....it likes to pass gas when it shouldn't (humor)

HAILERS

I'd like to give this site a big symbolic *Pat on the Back* for letting me post a jpg without a long confusing wait!

Rex4Life

OK, I sprayed starting fluid in the intake hose to the ACV and it stopped the engine at idle. Couldn't feel air sucking in but obviously it's leaking into the intake. Could this be why my idle vacuum is only 12"--on a 2000 mile rebuild?

BTW, which FSM are you getting these nice drawings from? The 88 FSM is crap compared to what you post up.

Scott

HAILERS

I think I'd take the acv off (just three fasteners), and take some RTV and block/plug the two holes that deal with the anti afterburn valves operation. If those two are blocked off, then there cannot be any leakage into the intake manifold. Or buy a new aircontrol valve.

Then again it's possible that the leakage is caused not so much by the valve itself, but could be a leak b/t ports on the acv due to the gasket not being in good condition? or?

I don't notice any problem with the anti afterburn disabled. I've never had any backfire etc.

87fsm from Mazdatrix. It's the eight and a half by eleven book, not the cutdown small pocketbook version.

HAILERS

OOOPS. REX4LIFE........One thing that slipped my mind. If you have a 86-88 car, it has a EGR valve. It might be possible that spraying the fluid in the airpump intake will cause the idle to rise/fall thru the EGR valve if its not blocked off.

Or a erratic idle can and will be caused by a EGR with a bad diaphram. You might check out the diaphram in the EGR by applying a vac to its diaphram and seeing if it will hold a vac.

Sorry 'bout that. I forgot about series four and the EGR being a possible bad actor during idle.

I don't think the EGR should be open at idle unless the diaphram in it is toast.