3.2 idle question......again.
 

Backgound: I have a hunting/surging idle on my 3.2. I just had the engine out and replaced almost everything. CHT, O2, hoses, fuel lines, seals, intake gaskets...etc. Before it went under the knife it had a surging/hunting idle, usually only when the engine is cold. It still does this now.

I did this:
http://forums.pelicanparts.com/uploa...1363367962.jpg

When I put the jumper on the idle just smooths right out. What is that telling me? I bench tested the ICV. It goes click/clack when you put 12V on it. It had the correct resistance as per bentley. It hums when it's plugged in. Could it still be bad?

I've been reading idle threads for the last couple of hours.

Hi ,what was the last time you have checked you fuel mixture?
You do have an oxygen sensor right? Try to disconnect it and see if the humming problem is still there
.If the set up is to rich the oxy sensor is trying to correct it.

Ivan

I can't say I have ever checked my mixture. Not sure I have the instrumentation for this.

well? it is kinda important to know your CO adjustment.
Did you say you do have an oxygen sensor right?
Try to disconnected it and see what is the idle doing...let me know

Ivan

I just played with it. When I started it surged as per normal and then settled out quickly because the engine was still warm. Idled fine. Unplugged the O2 sensor. Idled fine.

I have a univeral 3 wire o2 sensor. I have the black wire going to the green wire. I am hoping this is correct and this is also the only wire I disconnected.

Correct me if I'm wrong but doesn't the car ignore the O2 sensor when it is cold?

.well the circuit goes trough the oxy sensor and fuel is corrected all the time.You have to disconnect all 3 wires for adjsuting the fuel mix and if you have a catalyst you should measure before cat.
I do not know what do you have as an universal oxy sensor .Maybe a picture? Basically there is no need to have it plugged in at all.In Canada you do not have a smog inspection or do you?
i suggest you go and check your fuel mix....
Ivan

Bosch 3 wire universal 15726
https://images-na.ssl-images-amazon....1G6GXDEZ2L.jpg

Is there an easy way to check mixture without having a gas analyser?

do you have an air-condition?

Try turning down the idle air bypass. That usually cures the problem.

usually yes ..in this case the OP never checked the Co mix ...i bet the AFM box still have the original plug in it...

When you jumpered the test connector, you shut the ICV off, so that is why things settled.

Based on your tests, it sounds like the ICV itself is OK.

i would tell you how to check your basic CO adjustment ..but you did not answer my questions...

Ivan

The air conditioning had been removed

What am I missing?

It has nothing to do with mixture, so stop wasting your time!

Just for kicks I looked investigated my DME. I wanted to see where the fuel quality switch was. I played with it, I am 90% sure it was on setting 1 before I touched it. I made sure it's on setting 0 now.

No appreciable change. Thing still surges. I think I played with the idle screw too much and now I have a hard time getting it to stop surging when warm.

This car is depressing me.

well if you would have the a/c..you did asked how to check your fuel mix without the c/o machine,right?
Since you do not have a/c this test is not for you.
---------------------------

stlrj..to check if your fuel mix is too rich you run the warm engine on idle , you put your a/c on and using your hand(or Foot in the car) you step on the throttle to five some high rmp for a second or 2.
If the engine dies ,going to idle, the mix is too rich....little trick i have learn in my 911 practice years;-)
There is also one trick i leaned back in the 1970 by an oldtimer mechanic.In those day there were no gas analyzers...for this you just need a single match which you place behind the exhaust.....too long story ..................

Ivan

old man...did you disconnect the oxygen sensor -all connections?

Ivan

Hi Pete..i think he said his Idle control valve is working properly...
Ivan

If it were a mixture problem, it never would have passed smog or at least, at some point it must have passed.

hi..ST...you can pass a smog in CA if you have catalyst and oxygen sensor connected(even with higher fuel mix) but he is not in CA so the regulation are different in Canada i assume;-)
Also the fuel mix was never adjusted ,that would my 1st thing to go after since ha has check all of the above...
Ivan

car passed smog about 10 years ago....back when it was idling fine. It also had a cat back then.

So I played again with it this morning. I played with the mixture screw. I had the O2 disconnected and tried to see what reading I could get. With the mixture screw all the way in I was getting between 0.3 - 0.8. With the screw where it originally was I was getting around 0.03-0.06. With the screw all the way in it would not idle with the 02 plugged in. With the screw where it is it will idle fine with the O2 plugged in.

In every case putting the jumper in settled the idle right out. Could it be as simple as the ICV even though it passed it's bench tests? Anyone try using an non-bosch one (cheaper kind)?

Hi Old You basically did not adjust the fuel mix in 10 years? Correct? i suggest you you do the adjustment.
Set it around 1.0.... oxy unpluged.....
Are you now talking about mixture screw or idle screw??

here is some reading where the mix screw is located.

http://forums.pelicanparts.com/porsche-911-technical-forum/438195-idle-throttle-screw-setttings.html


and here you most likely have this plug still in .If not you just have to adjust it .If the plug is in you have to remove the AFM unit and remove the plug to access the adjusting screw for fuel mix.
http://img.pccreation.net/photos/201803031656443009.JPG

I have owned the car for 10 years and have never touched it. There was no cap on it so I am assuming a PO has touched it.

How do I set 1.0? 1.0 what? Volts?


I was talking about the mixture screw on the underside of the AFM.

ok now i know you know which mix screw .To set it you have to go to someone who has the gas analiser .Or you can play with it by listening to your engine .It has to be warm to adjust...oxy sensor disconnected and side plug jumped with your tool-wire.

Ivan

Unfortunately I don't have a gas analyser. I played with it and couldn't get a noticeable change by ear.

Just for fun I unplugged the CHT. It just belched out black smoke and didn't really idle. Just coughed. Mean anything?

My car will not start with the CHT unplugged.

How old are your spark plugs? If they are bad, even one, car will run terrible

Motronic really should not change much through the years. Must be something else. Do a complete tune up. That is what I did and car runs so much better . Also I installed correct 02 sensor.

Old..again if you disconnect the oxy sensor and insert the jump wire on side the idle should change ..Your??

Replace spark plug wires! Really!

They are about 30min old.

Depending on where the mixture is set disconnecting the O2 sensor does or does not have an effect. Jumping the wire always stabilises the idle out.

Ok..what i would really do..Find a nearby shop where they can check your fuel mix...you did a lot of things and even now you do not know what the mix is..That is very important for the engine running fine...and correct idle

Ivan

That was my conclusion as well. I will either have to wait and then go to a shop or order my own meter. Right now my car doesn't have axles, front suspension, brakes, or seats so it's not going anywhere soon.

it looks like you have something to do when is cold outside;-)

Ivan

+5C, sunny, and no snow here...unfortunately. I usually have tons of stuff to do when it's cold and snowy out.

Back to the question. If I had to buy a tool to check my mixture. Should I get a CO gas analyser (gunson gastester) or get some sort of a air/fuel guage perhaps even a wide band LM-2. I don't know much about these things.

My fuel pressure tester came in the mail. I tested the fuel pressure engine off, engine running, and vacuum disconnected as per bentley. Exactly on spec.

Search in my previous posts re surging. I had a similar issue and I tensioned the spring on the air flap in the afm. There were quite a few posts about the tracks on the afm being corroded and needing resetting. HTH .

AFM track has been 'shifted' over a mil or two.

As for messing with the spring I have read mixed advice over that. I will read more, however.