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Discussion Starter #21
Can you bench test the ICV with a 12v battery and test wires? This may help to settle if you have one, or two good-bad ICVs.
Just checked and they're both moving with a 9v.


With a high-impedance DVM the risk is low, BUT it's best not to tempt fate. I mean, if you slip and touch the probes together you've just shorted the ECU, and that's not good.
Good point. I had a cloth between the paper clips back-probing the MAF connector today.


This idle issue is mentioned quite a few times on the BB, but generally there's no follow up.

https://www.alfabb.com/bb/forums/164-168-1991-1995/216073-idle-air-control-valve-functionality-signal.html
 

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Discussion Starter #22

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This is the thread where it ended up being the fuel regulator.
easy enough to check....pull off vacuum hose from plenum and suck through it, if you can suck through it (or there is petrol in the hose) the diaphragm is split...make sure though, the hose itself is not split.

you could also clamp off the fuel return hose from bottom of FPR, see if your idle improves
 

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Discussion Starter #24
easy enough to check....pull off vacuum hose from plenum and suck through it, if you can suck through it (or there is petrol in the hose) the diaphragm is split...make sure though, the hose itself is not split.

you could also clamp off the fuel return hose from bottom of FPR, see if your idle improves
Looks like the FPR is fine. I had already changed the small hoses.
Clamping the bottom hose - no change.

Guess I'll check for leaks again - although I already sprayed all over.
If it was a leak big enough to stall the car wouldn't it also be noticeable when the ICV was disconnected?
 

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Discussion Starter #25
Is the O2 sensor involved with the idle when the car is cold? For example 1st start of the day.
 

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Before it started doing this, there was some hunting at idle, and some stumbling at idle when the fan kicked in, heater was on.

At that point I cleaned the ICV, throttle body, Oil Separator, VVT, and changed the plugs from Golden Lodge to NGK BP7's. The car felt much more responsive etc, but it started dying at idle.
Thanks
when you cleaned the throttle body, did you notice if the butterfly was closed?....my photo shows a throttle body off the car and you only see the tiny gap because I shone a flashlight behind for the photo.
I can imagine if the butterfly is not almost closed it would cause all sorts of idling problems.

The throttle stop is factory set and capped off, but some PO mess with them when there is a problem elsewhere, like a bad ICV or bad TPS etc.

check the throttle stop is just in contact with the throttle mechanism and not so far screwed in it is keeping the butterfly open.
 

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Discussion Starter #27
when you cleaned the throttle body, did you notice if the butterfly was closed?....my photo shows a throttle body off the car and you only see the tiny gap because I shone a flashlight behind for the photo.
I can imagine if the butterfly is not almost closed it would cause all sorts of idling problems.

The throttle stop is factory set and capped off, but some PO mess with them when there is a problem elsewhere, like a bad ICV or bad TPS etc.

check the throttle stop is just in contact with the throttle mechanism and not so far screwed in it is keeping the butterfly open.

As I recall the butterfly looked 'closed'.
This was messed with, however, I doubt that's the issue because I backed it off completely
and there's no change. I set it to touch + a tiny bit.

Plus, if I keep it running for a few minutes until it warms up,
it will idle with the ICV connected. It hunts a bit, but it won't stall.

It only stalls with the ICV connected when it's cold.
If that was the problem it would persist when it was warm, no?



To back up to the beginning:

When I first got it in summer, when the ambient temp was high, it idled with the ICV connected.
It was oscillating between about 900-1000, but it didn't stall.

It started stalling as it got cooler outside.

If I warm it first, either by keeping up the RPM's or disconnecting the ICV, it idles like before - some hunting but it doesn't stall.


When I first start it, it smells rich. About the time it warms up a bit and stops smelling, it will idle with the ICV connected.

So what controls the idle if the ICV is disconnected? With the ICV disconnected the idle won't drop below 1k even with the throttle stop backed up all the way.
 

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So what controls the idle if the ICV is disconnected? With the ICV disconnected the idle won't drop below 1k even with the throttle stop backed up all the way.
There's a rotating vane valve in the ICV. When the ICV is unpowered, it rotates to a fixed opening point. So it still flows air, it just doesn't control the flow. When you power it up it actually rotates to close that baseline opening and opens a gap on the other side of the valve.

I'm probably not explaining it well, but if you look at an unpowered ICV you'll see the opening where the air flows. The rotation of the valve is in the direction of making that opening smaller, not larger.

The throttle plate isn't supposed to be completely closed. There's a calibration to set the correct air flow at idle, but it requires Alfa flow tools that you don't have. Since it's been messed with anyway, maybe try *opening* it a bit more using the adjustment screw? It sounds like you're not getting enough air at idle, and if the throttle plate is too closed that might be part of the problem.

I would try progressively opening the throttle adjustment until it'll idle cold with the ICV connected, see if that makes a difference. Note that you'll likely need to adjust the TPS in parallel so that the idle switch is still closed at idle.
 

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Discussion Starter #29
There's a rotating vane valve in the ICV. When the ICV is unpowered, it rotates to a fixed opening point. So it still flows air, it just doesn't control the flow. When you power it up it actually rotates to close that baseline opening and opens a gap on the other side of the valve.
Alright.


The throttle plate isn't supposed to be completely closed. There's a calibration to set the correct air flow at idle, but it requires Alfa flow tools that you don't have. Since it's been messed with anyway, maybe try *opening* it a bit more using the adjustment screw? It sounds like you're not getting enough air at idle, and if the throttle plate is too closed that might be part of the problem.

I tried this before but I didn't change the TPS because the idle was quite high so I thought it's pointless.

However, it sounds like the ICV might actually be less open when connected than when disconnected - that's what I didn't account for.

I'll try increasing it by about 100-200 RPM and then adjusting the TPS so it knows it's at idle,
and if the ICV is less open that might actually drop the high idle.

But what I don't understand is - why is it Ok with the current settings when warm and not ok when cold.

Is the O2 sensor active immediately or only after it warms up?
 

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But Mad North-Northwest
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But what I don't understand is - why is it Ok with the current settings when warm and not ok when cold.
When the engine is cold you need a more open throttle to maintain the same idle RPM. The L-Jetronic manages this through the AAV, that lets in more air when cold and closes when the engine heats up. The Motronic does the same thing through the IAV.

In both cases, though, the throttle plate (and idle air bypass in the case of L-jet) need to be set right or there still won't be enough air to cold idle.
 

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Discussion Starter #32
Was looking at: https://www.alfabb.com/bb/forums/engine-management/197011-motronic-base-butterfly-position.html


This "If when you get it back together you find that the revs hang when you lift off the throttle, that's a likely sign that you need to open the butterfly a bit more."

That happens here so that might indeed be the issue.

The thread contains several procedures for adjusting the throttle stop - I'll go with Clayton105's.
Key part is blocking the ICV and then setting the throttle stop and TPS.
 

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Discussion Starter #33
this was a means of setting the throttle stop on a TS if you didn't have the factory gizmo.
I believe it would be the same on the S4, as they are not dissimilar and both are motronic.

the idea of blocking the ICV (not just disconecting the plug) sounds useful...
https://www.alfabb.com/bb/forums/1217184-post7.html
Oops, faster than me. Hadn't seen your post.

Yeah, that's the thing I didn't realize - the ICV was affecting the idle disconnected,
and may actually let more air through than when connected.

That would explain the stalling. Fingers crossed.
 

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Discussion Starter #34
Yep, that was it. Thanks guys.


RPM"s dropping fast to about 1200 RPM and then very slowly to idle speed would be a vacuum leak?
 

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Discussion Starter #35
The door chime with the door open and the key in is triggered by one of the switches at the front of the driver's door, and it's not uncommon for that switch to need a bit of cleaning.
The switch casing on this one has a wire which apparently is supposed to touch the mounting screw - seems kinda iffy.

Pulled the switch out and there's one cable but it's not connected to anything - maybe it disconnected when I pulled it out but there was no resistance.

The only other loose cable I found in there is a different gauge.
Connecting the 2 does nothing.

Do you know if the chime sound comes out of the same thing as the lights buzzer?
The lights buzzer does work consistently, but the chime thing was intermittent.
 

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Yep, that was it. Thanks guys.


RPM"s dropping fast to about 1200 RPM and then very slowly to idle speed would be a vacuum leak?
what!
after all that it was really a vacuum leak? .....Gubi suggested that way back in post #2

where exactly was it and how did you find it?
 

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Discussion Starter #37
what!
after all that it was really a vacuum leak? .....Gubi suggested that way back in post #2

where exactly was it and how did you find it?
Not even a leak - it was simpler than that. Had to raise the idle via the throttle stop
and adjust the TPS.

Basically, the throttle stop was set too low. As the ambient temps dropped there wasn't sufficient air to hold the idle with the ICV connected when the car was cold - ok when warm.

Looks like the ICV lets more air in when disconnected.

The key thing was understanding that the ICV affects the idle even if it's disconnected.


Re: leaks - might have some small ones - will have to check with the air pressure method,
but considering I can pull the OVS hose off and it doesn't stall, I'd say it was def. not a leak.
 

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Not even a leak - it was simpler than that. Had to raise the idle via the throttle stop
and adjust the TPS.
Basically, the throttle stop was set too low.
Ok, many thanks for the follow up and solution!
:)
 
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