RoughRex

I have a '88 N/A and cannot get air through my ACV to the split air pipe. I have replaced the ACV with a "working" used unit off ebay and still no luck they both just blow air to the silencer all the time.

So my question is:

What controls the ACV or could make it function improperly as described? Or did I just get another bad part off of ebay.

Your thoughts are appreciated as always.

Thanks guys.

*I thought I posted this earlier today but can't seem to find it so, sorry if this is a double post.

Icemark

The ECU controls the ACV.

If your old ACV had burnt up, it would take out the transistors in the ECU that control it

Carzy Driver

wow, that sucks.

HAILERS

This is a confusing post. What does *blow air just to the silencer* mean?

You know the ACV's air mostly goes to the exaust PORTS. To a hole in each exaust diffuser, located about an inch prior to where the exaust manifold mates with the exaust ports. In other words the ACV air gets mixed with exaust air prior to the 02 sensor and before the catalytic converter.

And the split air pipe gets and anemic amount of ACV air compared to what the exaust ports get.

The amount of air going thru the Split Air pipe rises dramatically when you put he transmission in fifth gear. The Split Air Solenoid gets activated anytime you go to ....fifth gear.

If I were you, one of the first thimgs I'd do is get a spare piece of vacuum hose. Remover each of the vac hose just above the ACV and put that hose on one nipple at a time. Suck on the hose and make sure it holds a vacuum. If they hold a vac, that's good.

Then start the engine and fully warm it up. Pull one of those vac hose off one at a time and make sure each HOSE is getting vacuum at idle. Rev the engine and the Relief hose hould lose it's vacuum, or just remove the blue plug off the Relief solenoid and it's hose above the ACV should lose vacuum.

What part of the FSM exactly is failing anyway? Most of the CONTROL of the ACV is thru the Relief and Switching solenoids. That's the Blue and Grey solenoids on the left side of the engine. They're controlled by the ECU but rarely fail. The two solenoids on the ACV are the Port and Split Air solenoids. Split Air controled by putting the gear lever in fifth and the Port Air by a signal from the ECU usually for short periods during sharp acceleration (memory). Neither of those two are a big player during Emissions testing.

RoughRex

hahaha...pardon my ignorance I got this car less than a year ago and it's my 1st rotary.

I thought the air going to the split air pipe IS the air that goes to the exhaust with the exception of some that goes to the reactor. Which makes sense to me even now as the two biggest lines that I know of to the ACV are to the silencer and split air...if only a nominal amount of air goes to the split air pipe, how does it get enough pressure in that big hose to override exhaust pressure and open the check valve...perhaps I'm misunderstanding? I guess there is the big hole behind the ACV but, I thought that went to the intake...not that I understood why...unless for the AAV but, it stands to reason what with the "Intake manifold check valve" blocking the path. At any rate I'm not arguing I'm just trying to let you know what I thought.

I had posted a while back that I was not passing emissions and Icemark had pointed out the secondary air injection issue. SO, I "tested" the ACV by disconnecting the hoses both to the silencer and to the split air pipe I then revved the engine at the throttle body and noted that air was blowing out only to the silencer. I then got a piece of 1" hose and ran it from the silencer port on the ACV to the split air pipe effectively sending air to the main cat at all times. Voila, I passed emissions with flying colors.

SO, there I was thinking that my ACV was bad but, now that I've replaced it...I'm wondering what else it could be. I'll be checking the Vac lines mentioned by hailers and here's hoping it's not the ECU b/c I'd hate to have to replace it. I don't suppose you rebuild those to Icemark?

HAILERS

My bad. THAT silencer.

IF both nipples above the acv will hold vacuum, then it's a matter of the signals from the Relief and Switching solenoids working right.

The Relief Solenoid is the one that puts a vacuum on one of those two nipples above the acv that caused the valve inside to stop the air from coming out the large hole and dumping it in the silencer. So check out that Relief diaphram inside the acv by sucking on the nipple that goes to it and making sure that it will hold a vacuum, indicating the diaphram is not ruptured and is functional.

Sorry 'bout that silencer/

HAILERS

Another thing you might try. A fully hot engine. A piece of spare vacuum hose. At idle pull first the most fwd nipples vacuum hose off the nipple. Plug the line. Install your spare vacuum hose. Suck on the hose. The air from the large silencer nipple should cease.

One little, tiny cavet here. I've actually forgotten if its the most fwd or the rear nipple that controls the Relief diaphram. Try both.

I'm talking about the two nipples directly above the acv. I'm also assuming the S5 acv arrangement is the same as S4.

RoughRex

ok, I just got home from work and checked for vacuum on the two lines coming out vertically above the ACV. No vacuum on either one at idle speed with the engine hot. I double checked the system by pulling the lines for both the Cruise Actuator and the Atmospheric Pressure Sensor which both had a good strong vacuum. I also put my finger over of the solenoid with the blue plug but, I couldn't tell if it was pulling air in or not. I'll have to go get a piece of vacuum line to try these other things....but, I can assume so far that if the ACV is good my relief solenoid related wiring or ECU is bad yes?

RoughRex

I got a piece of hose and tried pulling suction on each of the two lines above the ACV. I got no noticeable response with the forwardmost hose but the rear hose cut most of the air going out of the silencer so I want to say the Blue solenoid is the issue but, I pulled the one from my parts car and swapped them and nothing changed...I guess I need to bring home a voltmeter and test these guys the fancy way? Or....Icemark was right on from the start and it's the ECU.....*knocks on wood* Let me know if you have any more thoughts or if I'm not going the right direction here.

Thanks again guys.