ISV connector for 9A, which way round?

[Albie 0]

Just found the last bodger has fitted a new plug for the ISV without crimping down the connectors properly. After a history of occasional tickover problems I actually heard a slight crackling as I bent the cable near the plug. When I investigated the darned things just slipped out!

 

The plug is numbered 025 906 231 but I have found out this may be superceded to 443 906 232 on other setups. The ISV is numbered 048 133 455. I have the 2 crimp pins out of the plug without any damage and I have borrowed a good crimp tool from work to fit them properly. Now I need to know which terminal is which? (The picture below is not my own plug, mine is in much better condition than this.)

 

2.8l 24v Climatronic system.pdfISV AMP Plug.jpg[/attachment:1y4ty0a1]

 

The plug has a "1" and "2" moulded into the body at the cable entry point behind.

 

Plug Nos.jpg[/attachment:1y4ty0a1]

 

You can see the numbering of the terminals in these plugs. In the first picture pin "1" is on the Right. On mine, wires to it are coloured Blue/White and White/Black.

 

Logic tells me that as the ISV is basically a coil electromagnet pulling a metal plunger against a spring it shouldn't make any difference which wire goes to which. But experience tells me to get it right! I believe +12V is fed through one wire and the ECU controls grounding via the other wire so it could be relevant.

 

Can someone please tell me which way round the wires should be fitted. It would be enough to know that +12V should go to pin 2 say, as I can of course identify which wire is my +12V and take it from there.

 

One other thing which I find strange is that I have absolutely no idle adjustment on my throttle housing. There is no adjusting screw coming out towards the front of the car bleeding a little air past the smaller butterfly, or anywhere else for that matter. (I have run a few Sciroccos so I am familiar with this system). Common folklore seems to say that I should be able to set a slightly low tickover with the screw and the ISV takes care of the rest. Can anyone explain or am I thinking of something else?

[nocrap 0]

I can do the first bit for you! Just been out and checked, the black wire goes to the left on your pic and the white obviously goes to the right.

[Albie 0]

Thanks for the feedback Nocrap. The colours are a little confusing though.

 

My colours are definitely Blue base with thin White stripe, and White base with thin Black stripe. I would think that when you sat White you are referring to my White with Black stripe, and my Blue with White stripe is your Black.

 

You can't confirm which is the +12V when the ignition is on can you, then we can do away with any need for colours?

[Albie 0]

I have had another try to make sense of the schematics posted on the Russki VW site. I can't find any reference to wiring for the 9A engine. (so what's new), only to what seem to be the 4 cylinder SOHC and the VR6 models.

 

For all of them the ISV, or the Idle Air Control Valve as they call it, is labelled with different colours but with no pin numbers associated with the plug at the valve end. I think we must be able to assume that it makes no difference which way round they are connected, otherwise they would surely have numbered them wouldn't they?

[Blaklabel313 0]

for your second point.... the 9a isnt like a rocco in that sense....the 9a has an idle valve that controls part of the tickover but that isnt adjustable either.... why do you need to make it run slower on tickover?? is it too fast?? (possibly a stupid question)

[Albie 0]

I know the Scirocco has no ISV system and is completely manual on the screw. But I have read of Corrados with both an ISV and an adjusting screw. It is often advised to do away with the ISV and run only on the screw, particularly on American sites. This seems to me to maybe give the best of both worlds. My current problem is with a tickover which is fine for a while then drops, falters and dies rather than runs high.

 

As I understand it, the screw isn't there to set the tickover to its working level, it is to set it to a kind of lower minimum default level. The system I mentioned kind of sets 2 effective tickover levels, a working one and a sort of backup one which you hope you'll never need. Let's say the ECU wanrts to set the ISV to allow tickover at 950rpm. You disconnect the ISV and adjust the throttle screw to give a tickover of around let's say 800-850rpm. When you connect up the ISV again it will take over and adjust the tickover back up to 950rpm of course. If it ever gets into a stew and loses its ability to control for whatever reason it will stop passing as much air but the manual backup means the level cannot fall below 850ish, even with the ISV completely out of action and closed. There should be no problem with the ECU asking the valve to add just a little air to the intake to up it from 850 to 950 rather than the full quota needed to tickover, it's a continuous feedback system and is continuously self-compensating.

 

At the moment without the manual system, if the ISV or its ECU control fails then I am shafted! Some would say that the ISV only system is more sophisticated. Some cynics may say it forces you to buy another very expensive component when it fails in order to get your Corrado back on the road! ;-) Have you ever looked at how little is inside an ISV and how undemanding the construction is?

[Blaklabel313 0]

theres nothing too them at all i know, if its cutting out then try another idle valve....after all as youve said you cant adjust what you havnt got.

america didnt get the valver so im not sure what engine they are basing that on.

[Albie 0]

I wonder if I have cut in on a discussion about a different model, Audi maybe, and just assumed that because I recognised things they were talking about the Corrado? It could be, but the gist of the info was exactly as I described. "Why not do away with the ISV and rely on the screw adjustment solely like I do". It was even reported that it is a bit more difficult to do this in winter as the screw adjustment is not so temperature independent as the ISV.

 

If I can retrace my steps I'll post a link.

[Albie 0]

Durhhh! Yep I found it. In amongst a lot of links to discussion about 16V ISV problems I had come across this post on VWVortex. I didn't notice it was relevant to the CIS-E setup which does apparently have the ISV and screw adjustment. Sorry, latest in a string of senior moments.

 

http://forums.vwvortex.com/zerothread?id=3462207

 

Does make you wonder if a throttle body swap of some kind to one with screw adjustment isn't possible though, to reduce total dependence on the ISV. It may be a non-issue but it might just be interesting. Anyone any thoughts?