pd_day

iTrader: (6)

Hey guys, need some help.
My car have developed a weird idle.

It all started when my air pump went bad.
So I had a GOOD air pump put in, changed all the belts but the weird idle is still here.

BTW, where do the airpump pump air too? I found the inlet of where ever the airpump is puming air to real dirty. Could this be my problem?

The car drives ok but idles like ****. I would rock back and forth very violently and threathens to stall.

The SAFC states the O2 sensor voltage is 0.01 at idle...no fuel? Fuel filter was replaced 40k km before and voltage is normal when I drive.

I thought it was the pressure sensor. I swap another one in, still the same. But I did noticed that when I pull the vacume line from the pressure sensor, the car idles alot better! What can it be???

Also, this problem happens intermittently. Sometimes when I stomp on the gas hard and let go, it'll go away....

can someone help me?

thanks in advance

jmseven

Try your TPS.....chk it using the OHM method. Make sure your lowside is getting a signal at closed throttle, .8ohms - 1.02ohms. It should increase smoothly to 4.5 or 4.6 (WOT)

pd_day

iTrader: (6)

Thanks for the suggestion, I checked that on the safc already. It's good.

Aaron Cake

iTrader: (1)

Bad or sticking BAC valve...

pd_day

iTrader: (6)

My dash lights dim and idle drops when I press on the brakes.
Is that from the BAC valve too??

Thanks

pd_day

iTrader: (6)

Ok, cleaned the BAC valve last nite and the idle is still jumpy.
Here's more info I found out regarding my problem.

I noticed that the vacume in the car is higher then normal.
Usually it's at 540mm/HG at idle, but it's running constantly at 740mm/HG now.

I also noticed upon my crazy jumpy studdering idle, if I richen up the mixture to +30% at 1000rpm, the idle because really smooth and rises to 1000rpm instead of my normal 750rpm.

Do you guys think I have a vacume leak?
If I do have a leak, shouldn't my vacume at idle be alot lower?

Thanks

hugues

your lights dimming when you apply brakes, that means,
your alt is not outputting enough juice.

Check ur voltage at idle with no accessories on. Should be 14.4 (or more).
Turn on headlights, voltage should drop a bit.
Rev to 2000 rpm, voltgage should go back up to 14.4 (or more).
If does not do that, you alt is weak. Time to change it (along with battery).

TPS and BAC valve are first things that come to mind, but u say, they check out ok.
Look at this http://www.teamfc3s.org/info/articles/idle.html
for more info.

The engine will run better if you disconnect the pressure sensor because the ecu thinks you are under heavy load and compensates (more fuel and advance timing, I think). No a good idea to leave it unplugged.

Vaccum leaks:
Look for not so obvious leaks. In particular, ACV and EGR. On ACV valve, you have I think 3 vaccum activated diaphragms. On EGR, you have 1. if they are toast, you have a vacuum leak. To check for those, you have to apply vacuum with hand pump and see if vacuum holds.
But you are saying your vacuum has actually increased, so that looks like you're better than before.

Have you done a basic tuneup recently, spark plugs, wires, fuel filter, etc. You may need to do one.

the O2 sensor should not affect idle, so you can rule that out.

hugues -

Aaron Cake

iTrader: (1)

I still say BAC valve.

HAILERS

If your problem started with the new air pump why not start from there? There is only one place in the acv that air can get into your intake system. That the anti after burn valve. Inputs fresh air from the air pump during deceleration. If it has a leak, the working air pump could now be shoving air into the intake when it should not. Take the airpumps inlet hose off that runs b/t the airfilter and the airpump. Put your finger over the hose that leads to the air pump. Does the idle change????

I'd suggest pulling the hose off the rear of the air pump rather than the front,except I think its probably harder to get to. If it is easy to get to , pull that hose off instead of the one on the front. In other words kill the input from the air pump and see if things get better.


If you think its the bac, just pull the plug off the bac and see what happens. Better?Worse??????

hugues

Here is a pic of acv valve on s4

The arrow shows the path to the intake.

As you can see,
it is supposed to come from the air pump under certain conditions (vacuum to relief valve + air control valve).

Some exhaust port air may also find its way there if the check valve is not good (under certain conditions as well).

The above is what I understand. If I am wrong, please somebody point it out. thanks.

I have read the original post again, but now I am confused. You say you changed the air pump and idle is STILL weird. So, it was weird before you changed the air pump. When did the idle start acting weird ?
Just wondering.

Hugues -

pd_day

iTrader: (6)

I got my funky idle when my airpump went dead.
Maybe some crap from my dying airpump got into the ACV and clogged.
There were a lot of crap in the inlet where the airpump pumps air to.
I cleaned that out yesterday and was still the same.
Maybe I have to take the lower intake manifold alone with the ACV off completely and see. I can install my pineapple sleeves at the same time...heheh

With the BAC valve cleaned, the car seems to be a tad smoother....but still sucks

pd_day

iTrader: (6)

I think it's my port air and relief air valve giving me ****....

maybe they are stuck close so I have more vacume at idle....

Anyway to clean them without taking it off the Lower intake manifold?

HAILERS

I think you are misunderstanding the acv. The PORT AIR.......is air directed into the EXAUST manifold. It will not effect your idle. And the relief air valve if it fails open will just dump the air pump air overboard.

The only way I see the acv effecting the idle is if the poppet for the anti afterburn valve is stuck open or cracked open. That is the only passage to the INTAKE air in the manifold. You can prove this by just removing the airpump air from the acv. If the problem is alleviated, then that might be the culprit.

Its not a big deal to see if the relief valve in the acv is working or not. Idle the engine, pull the large exaust hose off the acv, then pull the blue solenoid connector off. Air should spill overboard when the plug is pulled and barely blow overboard with the connector on.

You should have a vacuum on both the relief and switching vac lines on the acv at idle. Check for that and also pull both lines off and put a piece of vac line on the nipples on the acv and see if they will hold a vacuum.

hugues

You should really get fsm for your car
www.fc3s.org under how-to->manuals (get 89 one, chapter about fuel and emissions)

You'll find everything you want to know about the ACV valve (how to check it and take it out)

HAILERS is right on the money.

If you look at picture I put earlier in thread,
the AAV (anti afterburn valve) allows air to flow into the intake (under certain circumstance) [I even put an arrow to show the path]

If the relief valve is open (vaccum on its diaphragm)
and the AAV is stuck open, you have an open path to the intake

Now, I kinda disagree with HAILERS

I don't think that s the only possibility

It is possible exhaust gases can also creep into the intake if the check valve (the 1 in the port air duct) is blown and the switching valve is open and the AAV is stuck open (in that case, the relief valve could still be closed and functioning properly)

As HAILERS suggested, just disconnect the air pump and see what happens. If it does not improve, check the check valve for leakage of exhaust gases.

Hugues -

pd_day

iTrader: (6)

ok, I pulled the air hose from the air pump to the avc and now it idles rock solid at 750rpm without any extra fuel...

so I think the culpit is the after burn valve..
I am going back now to verify...

pd_day

iTrader: (6)

Sorry, what I mean was I pull the hose from the airpump to the ACV and the idle still sucks. I put my hand on the ACV opening and I can feel air being sucked in.

Turned off the car, pluged the ACV and started the car again.
Idle is rock solid at 750rpm!!!!!
SO the air is leaking from the ACV or AAV or somewhere....

Nevertheless, I have to get the ACV replaced rite? It can't be cleaned?

HAILERS

Yes. You probably need a new one. You might take it off(three nuts) and make or buy a plate of metal to cover where it was. This will give you time to invest, gamble or steal a large enough amount of money to buy a new one. Beware used ones. They usually have cracked diaphrams inside. The anti afterburn valve is a part of the acv. Try cleaning it. Never done it myself. You've nothing to lose.

EDIT: I take that back. You have a n/a. They don't destroy the diaphrams as good as the turbo model does. You might find a good used one.

dr.jones63

I dont know if this is your problem but, the heatsink gizmo behind your passenger headlight regulates voltage to your fuel pump. High airflow = more voltage to your fuel pump. A known weak area for 2nd gen cars. Check out : http://www.teamfc3s.org/talk/turbo/messages/3829.html

hugues

As HAILERS said, I would just replace the whole ACV unit with a used one. Just make sure the 3 diaphragms hold vacuum when you buy it and that the check valves are good.


Hugues -