Hi everyone!

What would happen if disconnect the ACV's electrical plug and take off the hose that runs between air-pump and ACV?

The car is 88 GTU

Thanks!

 

youd have an annoying huffing sound from the pump, the hole created by the ACV will make your car sound like a tractor, and the acv will no longer do what the acv does.

what did you think wwas going to happen?

 

Actually i've meant if ACV is still in place but electrically disconnected...

You see i don't have the stock cats, and i'm using a Euro LIM with 5 & 6 butterfly-valve ports, so i don't need an Airpump anymore... Eventually it did happend that i've been forced to disconnect the ACV, but left it in place to block it off later...

So actually the question was - what the downsides could be in this case? I mean i'm not sure in which position internally ACV stays when it's unpowered and it might be possible that something's working wrong in this case, like fresh air that suppose to be added to exhaust manifold at certain circumstances only, could be happenin' all the time... Any ideas?

I'm just gettin' really bad MPG and engine runs rough with rough idle... Checked too many things to list here, including basics like cleaned injectors, spark plugs and wires, water thermo sensor, etc...

 

The ACV consists of five internal valves. Two are electric solenoid valves, two are pneumatic valves actuated by remove solenoid valves (the ones with the blue and grey plugs) and one is operated directly by manifold vac. Unplugging the two electric solenoid valves won't have much effect at all, since they have minor functions only.

Sounds like you have a vac leak.

 

Well, thanks NZ, it sounds like it, but since i installed a silicone vac lines all around i don't really think so... It just might be engine's wear...

 

There are plenty of other places to get vac leaks other than rubber vac lines. Everywhere between the AFM and engine ports would be a good place to start...

 

Thanks NZ

 

A very common *vacuum* leak is the anti afterburn valve in the ACV. It's the ONLY part of the ACV that feeds air to the INTAKE manifold air, and it only does that during deceleratiion, UNLESS the valve is not seating like it should, then it becomes a *vacuum*/air leak. It will only be noticable at IDLE.

So, if you disconnect the airpump (just take its belt off and leave the rest in place) and now the idle has changed noticeably, then you've a anti afterburn valve leaking. Take action.

 

Thanks HAILERS! Will check that as well!

 

If i'd have such a leak would it be cured by installing ACV block-off plate, right?

 

Yes, of course..

Your S4 has no feedback from the ACV solenoids, so you're good to go.

The S5 guys will get a CEL unless dummy resistors are added to the solenoid circuits.

 

Thanks! I've got one more question... My car has sitted for one and a half year and after i started it, the smell from the exhaust was really bad and i'm pretty sure that i was running way to rich... but the ECU has read no errors, after that i changed my AFM and the smell from exhaust turned to be not so bad, but it's still there... So my guess is that first AFM i used was miscalibrated somehow... Is there any way of overhauling it or tweaking except for buy a new one? And how often they do fail actually?

 

The FSM has some tests in the "fuel & emmissions" section.
The S4 AFM has a removable cover, so you can clean the resistor.
Be very gentile.

Try to find a can of spray contact cleaner.
Years ago it was called TV tuner cleaner.
It's aslo good for lock switch position contacts, radio controls, AC controls, TPS resistors.

 

I did opened it eventually and found it pretty clear... Is that liquid is the same as WD40? BTW i have another spare euro-spec AFM, i opened it as well, and checked resistence with DMM of all of the connectors on both, for me they've behaved absolutely identical, but when i'm trying to plug in a euro-spec AFM i see an error code for AFM, so it's not working... BTW internally they are a bit different in mechanical part, but PCBs are the same as well as connectors...

 

WD40 will clean the resistor, but the oil will cause problems.

If you can't find contact cleaner, or electric motor cleaner, use a small shot or brake cleaner.
Remember brake cleaner will melt many plastics.

 

Thanks for pointing that, mate! Will try to find a contact cleaner! So you think that should restore the AFM?

BTW have you ever tested AFM with DMM by yourself? I did that by FSM, and the weirdest thing i discovered is how resistance is changing when i'm pushing the flapper in gradually... I think FSM says that it should change from 500ohm (closed) to 5-6kOhm (open) (i don't remember exactly), but it doesn't says exactly HOW the resistance should change... and both of my a-spec AFM was reading really weird... I would describe the readings as a saw if i'd build a graphic... while i'm gradually pusing in the flapper it starts where it should - 500ohm i think and raises until ~5-6kOhm... and suddenly back to where it has started and climbing again... and has repeated several times until i pushed the flapper fully in... I'm still wondering is suppose to be like that or nor :-/

 

Yeah. The ohm meter will rise/fall as you push the flap. Do this: Connect the connector to the afm and turn the key to ON. Monitor the VOLTAGE output of the afm at the ECU pin 2E. You'll find the voltage will fall in a linear fashion as you open the flapper.

 

Thanks HAILERS... So how would you recommend to define is AFM is good enough or not... I mean the resisances are all in spec... But you know... It is an old cars... Something weird can come out...

 

The resistance sweep should be linear as the door opens.
This is also true for the TPS.

If there are dropouts in the values as you work the sensor, it is bad, but maybe can be cleaned.

 

It's easy to see you've never checked the resistanve of the afm out EVER.

 

Actually you might very well have, but not on a series four afm. I know NOTHING about series five plastic/cone afm's.

 

Other than checking out per the fsm I have no real other way.

The potential problem is that someone can go to the internals and change the spring tension but the results won't show on the fsm checks. But when you go drive the car the spring tension will make a big difference is they moved the tension more than one cog one way or the other.

My shade tree method was to find a afm that had never had its ihternals messed with. I stood it on end and put the electrical plug on the afm. I turned the key to ON and then placed a socket on top of the flap. Of course the flap opened some with the weight of the socket, but I made sure the socket did not touch the sides of the afm so its full weight was on the flap alone. Then I looked at my SAFC which was set on SENSORS and observed the voltage.

EDIT: This from a old thread by a neutral party......"Wrong again.&nbsp The 1986-1988 Zenki FC's run a logrithmic resistance signal that fluctuates several times from 0 to 5k-ohms(?); this is not a simple potentiometer.&nbsp Also, the AFM input is strictly for fuel; it has nothing to do with timing.&nbsp Timing is controlled by boost/pressure sensor and RPM, primarily."

Like I said, series five might very well be different.


So I figured that a normal afm with that given weight would cause a output of whateever voltage I saw.

Then I took one of my many suspect afm and put the same socket on its flap and compared the voltage output of that afm vs the one that had never been messed with. Then I changed the spring tension on my suspect afm to match the good one.

That's pure shade tree mechanics. You can buy rebuilt afm. There are places out there that do that for a living.