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old man neri's Avatar
 
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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:


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.
Old 03-02-2018, 01:23 PM
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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
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Old 03-02-2018, 01:28 PM
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I can't say I have ever checked my mixture. Not sure I have the instrumentation for this.
Old 03-02-2018, 01:35 PM
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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
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Old 03-02-2018, 01:47 PM
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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?
Old 03-02-2018, 02:20 PM
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.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
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Old 03-02-2018, 02:30 PM
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Quote:
Originally Posted by proporsche View Post
.
I do not know what do you have as an universal oxy sensor .
Bosch 3 wire universal 15726


Quote:
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
Is there an easy way to check mixture without having a gas analyser?
Old 03-02-2018, 02:40 PM
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do you have an air-condition?
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Old 03-02-2018, 02:49 PM
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Try turning down the idle air bypass. That usually cures the problem.
Old 03-02-2018, 02:50 PM
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usually yes ..in this case the OP never checked the Co mix ...i bet the AFM box still have the original plug in it...
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Old 03-02-2018, 02:59 PM
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Quote:
Originally Posted by old man neri View Post

When I put the jumper on the idle just smooths right out. What is that telling me?
When you jumpered the test connector, you shut the ICV off, so that is why things settled.

Quote:
Originally Posted by old man neri View Post

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?
Based on your tests, it sounds like the ICV itself is OK.
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Old 03-02-2018, 03:39 PM
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i would tell you how to check your basic CO adjustment ..but you did not answer my questions...

Ivan
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Old 03-02-2018, 03:49 PM
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do you have an air-condition?
The air conditioning had been removed
Old 03-02-2018, 04:22 PM
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Quote:
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i would tell you how to check your basic CO adjustment ..but you did not answer my questions...

Ivan
What am I missing?
Old 03-02-2018, 04:25 PM
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What am I missing?
It has nothing to do with mixture, so stop wasting your time!
Old 03-02-2018, 04:34 PM
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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.
Old 03-02-2018, 06:28 PM
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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
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Old 03-03-2018, 12:09 AM
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https://www.youtube.com/watch?v=MRZG-s_55CU
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Old 03-03-2018, 01:58 AM
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Hi Pete..i think he said his Idle control valve is working properly...
Ivan
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Old 03-03-2018, 02:16 AM
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Quote:
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It has nothing to do with mixture, so stop wasting your time!
If it were a mixture problem, it never would have passed smog or at least, at some point it must have passed.
Old 03-03-2018, 04:13 AM
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