[wildcat]

I checked the idle with the ICV active, then disconnected it and checked the idle and it was low.  So I readjusted the idle to approx. what it was with the ICV connected.

 

I have had no adverse effects.  The machine is running really well, no stalls, no rough idle and no lag.

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[flash]

just realize that it is there to balance the air coming off throttle, and just off idle.  if you stuck a probe in the tailpipe, i am betting you would find it to be rich off the bottom, which will cause you to fail smog.  this range is a particularly critical area of concern in california

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[jfrahm]

The idle valve is a common enough part.  One of my cars came to me with a BMW E30 valve in it, did not fit properly due to the hose connections but it worked.  They can be aggressively cleaned on the bench or replaced with a Saab or Volvo or whatever part.  It is possible to finagle them out of the car with the intake installed.  I do not think you can spray them enough to clean them adequately when installed, I soaked one's business end and used a toothbrush to clean it decently, tested with a 9v battery.

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[wildcat]

I took mine out, but not apart.. that is probably the next thing I'll do.  And driving around with it disconnected I've come to the conclusion that two things happened apparently at once.  The M.A.F. wire broke and the Idle Control Valve was on its way out... all the problems I was having with idle were due to the ICV and not the M.A.F. (either with the copper or the platinum).  So I will follow sage advice and see what I can do with it, and see what the options are in replacing it. In the meantime it is interesting to note that the car runs fine without it, even if it does so a little rich.

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[ds968]

smog tests and gas mileage efficiency aside, I'll take running rich over running lean ( risk of engine damage ) any day any time  

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[wildcat]

Then you might find it comforting to know that if the ICV goes south on you, you can just disconnect the wiring to it, take the throttle body off and turn the set screw 1 1/2 turns approx and you're back in business. But you've got to leave the plumbing connected as it does provide just the minimal amount of air into the manifold to get you started. The DME does the rest.

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[kwikt]

Good to know

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[wildcat]

yeah kinda makes you wonder why there is a ICV at all... it complicates the regulating of idle by adding another layer... the DME and throttle body are more than up to the task. The problem is that as the throttle body was designed, when closed the throttle body doesn't allow air into the manifold... by turning the set screw you are in effect creating a small opening in the butterfly valve to allow air in to start, and that becomes your idle setting. Another gnome dictum from on high.. "if there's a more complicated way of doing it... proceed."

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[flash]

it's an emissions thing.  without the ICV, the idle air is not regulated as well, and therefore will vary to the extent that the emissions are adversely affected.  with the throttle plate kicked open, unless you recalibrate the TPS, the ECU will "think" that you are off idle, and will enrich things accordingly.

 

as for the ECU handling things, it is extremely primitive, and its sampling rate at idle is very slow by modern standards.  it does not do a good enough job without the ICV.  further, at low temps, the car will not start or idle as well.  in a 6 speed, this causes stalling.  in a tip, where the idle is set a bit higher than in the 6 speed, and also has more reciprocating mass to keep the engine running, this may or may not be a problem.  we won't really know until winter.

 

kids - do not try this at home.  fix or replace your ICV.  it's not that hard to get out of there, and you'll be happier in the long run.

 

do it once - do it right - don't go back

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[wildcat]

They claim its an emissions thing... but follow the logic... the ICV is controlled by the ECU.  The ECU may be primitive by today's standards but it is hardly primitive for what it was intended.

 

Basically the ICV is like a miniature throttle body and if you look inside you'll see a slit where the air goes through, if you're daring you can stick a probe in and move the "shutter" which allows more air in. Its the ECU that's controlling this little beast.  So why not just take direct control of the butterfly valve? Having taken it apart  and adjusted the set screw for idle I am well aware that it is a redundant bit of hardware. It is not crafted in a way that would make it superior to the control of the butterfly valve.  In the old days with carbs the fuel and valve worked in tandem and also provided idle.  With a computer regulating fuel and air its more precise and the ICV is just another ad hoc piece of non-sense. 

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[flash]

it is NOT a redundant bit of hardware.  it absolutely does control the air better than the gross control of the throttle plate.  the smallest movement of the throttle plate alters the mixture.  it is connected to the ECU via the TPS.  unless you recalibrate the TPS, the ECU will think you are off idle, and will add fuel.  even then, i don't think you'll get it right.  i know i had this problem when i was tuning the supercharger kit.  i had a bored out throttle body that cracked the plate open just a touch, and it threw the mixture all to hell.

 

you are thinking in terms of carbs, but fail to realize that in those days we were not concerned with 14.7 mixture.  it was common to float between 12 and 13.  it didn't matter until emissions controls came into play, and then there was an air injection pump, driven off the crankshaft, and an EGR valve, which together did much of what the ICV does, but the ICV does it much better

 

again, just because it starts and runs, does not mean that it is working.  again you need to take readings at the tailpipe.

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[wildcat]

Essentially it is an automatic choke, and absolutely is redundant in the sense that it is not needed. You can by pass the ICV but you'll have to warm it up manually and that isn't as precise as what the ECU will do. The amount of time involved to warm it up is less than a minute unless you're in a colder climate. Adjusting the throttle body to allow air in will increase your idle rpm and that will increase emissions but that's the limitation imposed by design. If the throttle body was designed to allow air for idle it wouldn't be needed at all.   Emissions are handled by the ECU. The argument that it is essential for emissions and that the throttle plate is insufficient to the task is absurd. 

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[flash]

it IS needed for CORRECT operation.  get a danged A/F meter hooked up and see for yourself

 

i am really getting tired of having the same discussions about mickey mousing repairs, and what YOU think is fine.  it is clear to me that you don't understand how some of these things work.  that's fine, and a part of the learning curve with a new car, but please stop trying to tell people that these methods are ok.  if you want to ruin your car, you have that right, and can do whatever rubber band and bubble gum repairs you want.  it is NOT the way we do things here.

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[wildcat]

Right, the M.A.F. I repaired works as its supposed to.  Hardly a bubble gum repair. If that is the way you wish to categorize my efforts as a disclaimer that is your right.  I have not put anyone's car at risk.  I know I don't have all the answers but I work through them.  I have investigated the ICV in depth. The relationship between the ECU and these different elements is fascinating.  Nothing like hands on either.  I also took apart the ICV and repaired it.  It has two armitures, a small one in 3 sections which were scoured and a large one with a metal housing.  This had some rust on it. I took 3000 sand paper and took out the scouring and the rust and put it back together.  I looked at the "points" which are the contacts (or brushes) for the small armature. Very little wear.  This is important because it determines how active the ICV is. This  lends support to the notion that it is an automatic choke more than it is an "idle control valve".  It also lends support to the contention that emissions have nothing to do with its function. But this can be tested without checking the tailpipe emission numbers.

 

There is a simple test in 3 parts.

 

A basic assumption is made regarding two factors.  First that the ICV is not gummed up, if it is the ECU will try to compensate by opening the valve.

Second that the idle set screw is at its factory setting, that is neutral so the throttle plate is closed at idle.

 

The first part is to disconnect the plug connected to the ICV when the engine is cold.  This is not to be done with the engine running.

Crank it a few times and note the engines response. Don't give it any gas.

 

The second step is to reconnect the plug to the ICV.  Then restart the car as you normally would.

Let the car warm to operating temperature.  Note the RPMs at idle. Stop the engine.

 

Disconnect the plug to the ICV again.  Start the car... it should fire right up with a little gas.  Let the idle settle. Note the idle.

 

The idle should be the same.  That is because once the car is warm the ICV goes to its stand by position which is 3/4 closed.

 

All this implies that its function is not to regulate idle, except during warm up. The ECU sends a signal to open up the valve when its cold and mixes in more gas.

You'll note that idle is higher at start up and tapers down as the engine warms. When warm the idle is the same with or without the ICV connected.

 

In my previous post I mentioned turning the set screw 1 1/2 turns. This is not necessary provide the ICV is not gummed up.

 

I could resent your implications but I know I'm on solid ground.  If there is any aspect of my projects that you think falls in the "bubble gum repair" category we'd

all be enlightened if you'd share the specifics.

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[vliegwielolaf1234]

Maybe this should be in a differnt topic !

 

Has nothing to do withthe throttle lag from idle .

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[flash]

wildcat - you have absolutely no idea how the ECU works, and are wrong about the ICV.  i experienced the extreme of situations of how it is necessary when i was tuning the supercharger.  you may not see its need, but it is there.  the fact that you have a tip limits your ability to see that.

 

the higher idle at startup is programmed in.  there is a whole map, with a timer, for that.  it is not directly related to the ICV.

 

as for the bubble gum repairs, you still don't know how the MAF works.  until you get mixture readings, you won't know.  your assumption that because you can start the car and go to the grocery store without incident is NOT indication that it is functioning correctly.  that's like saying you don't have a disease, just because you've never been tested for it.

 

show us air/fuel readings at start up, idle, and running down the road.  then we'll have something to talk about.  it is not in the best interests of the community to suggest repairs other than as indicated by the manufacturer, without data to support the validity.  anecdotal reference and opinion are insufficient.

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[wildcat]

On the contrary I do.   When you turn the ignition key, without using the accelerator, the ICV provides the air to the engine. The ECU sends a signal to open it further for startup.  When you put the car in neutral, the throttle plate is closed and again the engine gets its air through the ICV.  I've provided the test. See for yourself.

 

Your intimidation techniques and snide assumptions don't do anything for your argument.

 

I live 2 blocks from the San Diego Yacht Club.. a lot of Porsches in the area... you don't need to take it personally.

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