OOOO!! What does this do?*PIC*

[Kinetik_tsi]

Well, I got my car back from the mechanic, and it's running fine after I got bent valves replaced, and new belts and all that. When I got the car home I noticed that this connector on the intake manifold wasn't pluged in, so I plugged it in. It ran fine for a little while, then it started to idle like crap( like @ 200 RPM). I reset the ECU, and the car wouldn't turn on any more. So I unplugged this connector here and tried again. No dice. Then I let it sit for the night and tried it again in the morning (connector still unplugged) and the car fired up, still idling like crap, but after a couple of minutes idle went back to normal and it stayed like that. So I am driving around assuming the mechanic left this unplugged for a reason, and this is ok for my car.

Cliff notes:
Car runs like crap, or does not turn on at all when this is plugged in.
What does this connector do?

 

[Willjs7]

That is the ISC connector attached to the ISC motor.

 

[TSiAWD666]

That sensor detects when the throttle body is closed. Why it's so important (or not) I couldn't say, as it's a 1g thing. I'm sure someone will have a better answer for ya

 

[92redman]

It will raise your idle speed if disconnected and will also take your engine longer to slow down when you let off on the throttle. Also you can adjust your idle speed with it because it actually stops the throttle plate. You can only back it out so far but turning it down will slightly raise your idle. That's about all I can think of, you can still drive fine with out it but it will just have some affects on your rpms when the throttle is closed.

 

[92redman]

If you want to know how to check to see if it is bad, let me know, otherwise I guess you could just leave it unhooked.

 

[Kinetik_tsi]

Cool. So it won't be a problem if I leave it unplugged? I kinda like the idle speed it stays at right now(600-700rpm varies with accesories).

P.S. How CAN I find out if it's good or not? I guess it'd be good to know.

 

[steve]

It's the Idle Position Switch and it used my the ECU to know when the throttle butterfly is closed for a varity of things like deceleration, controlling engine idle speed, emulating a dashpot, etc. It's a simple but important sensor. I can cause a CEL if disconected.

My guess is that your mechanic set your engine idle speed with it disconnected and now the BISS is in too far to idle correctly under ECU control or your ISC has problems too.

You can read the state of the IPS with a datalogger or by checking that the connector is grounded normally and opens with a little throttle petal.

Depending on what tools you have you might want to try following the BISS VFAQ and reset your idle speed or print it out and take the car back to your mechanic for him to do it.

Steve

 

[audiodude123]

just screw in the BISS then back it out 2-3 turns then adjust the idle switch so that it just closes when the throttle plate is completely shut then test with a multimeter and finally adjust your throttle cable using the multimeter to make sure it's not too tight.

P.S. your gas economy will increase because it will actually idle instead of the computer thinking you are lightly gassing the engine

 

[patriot]

Originally posted by audiodude123
just screw in the BISS then back it out 2-3 turns then adjust the idle switch so that it just closes when the throttle plate is completely shut then test with a multimeter and finally adjust your throttle cable using the multimeter to make sure it's not too tight.

P.S. your gas economy will increase because it will actually idle instead of the computer thinking you are lightly gassing the engine

but please, before you just screw in the biss screw, read the vfaq. then you will find out that if you dont essentially disconnect the ecu before you do this, you will be competing with it to control idle speed. all that is required is two jumper wires with gator clips about 1 foot long each

 

[steve]

Originally posted by audiodude123
just screw in the BISS then back it out 2-3 turns then adjust the idle switch so that it just closes when the throttle plate is completely shut

Unless you have reason to believe that someone has moved the IPS from where it was set at the factory or you have to replace it, don't touch it!

The IPS serves two functions on a 1G. The first we discussed, the second is the stop for the throttle butterfly. It keeps the throttle plate from cutting into the throttle bore and hold the plate/butterfly open a specific amount to allow air past. This is a critical adjustment that effects how the three other air bypasses (ISC, FIAV, and BISS) interoperate. The manuals procedure for setting the IPS is to connect up a meter and back off the IPS and make sure the throttle is fully closed. Adjust the IPS with the thottle closed until the IPS has continuity to ground, then turn it in an additional 15/16 turn and lock it down. That 15/16 turn sets the amount it holds the plate open.

Steve

 

[Kinetik_tsi]

Cool. Thanx.

I guess I can just do an idle adjustment. I had done an adjustment before the car broke down because I had idle surge.

 

[92redman]

Yup, those are the correct procedures. If you can't get it to have continuity by adjustment, then it is probably bad. You may want to take off the t-body elbow to verify that it is actually making contact with the throttle butterfly before replacing it.

 

[Kinetik_tsi]