Idle Valve

soxnail · 02-13-2007, 04:58 PM

Hi guys, I have been chasing a vacuum leak for a while. It turned out to be the ISV. So before I got a new one I decided to try to fix it. any way it was a crumbling dry 'O' ring.
I opened the valve by bending back the tabs and found the o ring the pictures are under...hope this helps some one before they drop 150 plus bucks on a new one.
Sox

This is the valve with the tabs bent back

Cleaned up valve and the position of the o ring

busted o ring

nynor · 02-14-2007, 12:57 PM

strong work! i'll be going through my entire intake soon.

soxnail · 02-15-2007, 01:01 PM

Ok got the new o ring on it and put it back together, this fixed the leak at the bottom of the valve, but there is still a leak at the top where the connector goes. So here is the final step. Use a small Q tip and put plastic cement around the connector and very very carefully put it in the connector, next to the three pins in the connector. Make sure that you do not get any on the pins !!. (if you do clean them with a small flat head screw driver). This should fix the final leak. See the pic.
Sox

ae1969 · 02-15-2007, 02:46 PM

.... good job sox.

The funny thing is that even the new ones leak out the top.

soxnail · 02-15-2007, 02:51 PM

Thanks ae1969 I am on a mission !! no leaks. Lets see how far it gets.
Sox

nize · nize's Garage

hey this is a great writeup, maybe you can submit it to clark so he can add it to the how-to's (you will get credit for the write-up too!);
http://www.clarks-garage.com/

soxnail · 03-01-2007, 04:16 PM

Unfortunately The cement on top of the connector did not last it must not like the high temp environment under the intake manifold. So the connector on top of the isv is leaking again. Any one point me towards a glue/cement that will handle the temp?
Tia Sox

nynor · 03-02-2007, 05:47 AM

jb weld.

nize · nize's Garage

ah yes, good stuff.

soxnail · 03-02-2007, 09:18 AM

Thanks Nynor...will do next time I have the intake manifold off. Its been on an off more times than a wasted prom queens drawers

Sox

soxnail · 04-30-2007, 01:41 PM

And finally the last step. The folks at Bosch good as they are did not add heat sinks to the Darlington transistors that are used to drive the ISV. This causes a problem over time of the PC board itself getting heat damaged and also if the ISV is sticking or has any problem it can burn out the drive transistor.

You can see the board is damaged.

Now replace the two "ON 588" transistors which are Bosch in house parts with "2N6386" transistors. Get two slip on heat sinks to go on them and you will end up with the following.

One final thing you can do a low tech test on your ISV.
With the ignition on but the car not running if you touch the ISV it should be vibrating.
Sox

Zero10 · 05-04-2007, 02:56 AM

Excellent write-up, I suspect my ISV is fuggered, since I have a random severe vacuum leak, and I can't pin it down anywhere else. I assembled everything such that I can actually remove the ISV without removing the intake manifold, so I think I will investigate this soon

Just curious though, why should the ISV vibrate with key on, engine off?

nynor · 05-04-2007, 05:27 AM

because the electrical valve is fluttering?

soxnail · 05-04-2007, 06:57 AM

Yup even with the engine not running the ISV is getting the pulse train, its moving back and forth very fast ( just a little bit) and you can feel it. With the car running there is to much other vibrations.
Sox

soxnail · 05-04-2007, 07:08 AM

here is what it looks like key on engine not running.

nize · nize's Garage

i have my manifold off now. is there any way i can check the isv without buying a new one?

i'd hate to drop $200 if it's unnecessary.

soxnail · 05-04-2007, 11:05 AM

Yup. You will need a digital VOM some alligator clip leads and a 10 ohm 10 wt resistor.
Also if you had a source of air it would be good but not totally esential.
!) On top of the ISV there are three flat pins in the connector. Take your VOM and put the alligator clips on each of the leads (one on black common and one one red signal). Set the meter to measure ohms and connect the common to the center pin on the ISV connector. Measure the resistance between it and the two pins in the connector (on each side of it) . It should measure 20 ohms one one side and a little higher on the other may be 24 ohms or so. The numbers are not important but it should not have less than 10 ohms or more than 50 ohms on either side. That means that the coils in the valve are good.
2) Now hook up the common (center pin) of the ISV to the positive side of a 12v source. You can use the car battery. Hook the negative side of the battery to the other alligator clip hook up the 10 ohm resistor to other side of the same clip. You will have a a circuit that is connected to the battery on one side and the other will be open. Now momentarily touch the open end of the resistor to either one of the two side pins on the ISV as you go back and forth the ISV will open and close with a loud click and if you are holding the valve you will feel the rotor in their turn. That means that the valve is functional.
3) If you have an air source connect it to the side of the valve that goes to the hard pipe before the throttle body. Let the air flow into the valve not much is needed, and repeat the above test. The air should flow thru freely with the valve turned on (a click that opens it) and the air flow should pretty much stop when you cycle the valve over to close. (there will be some leakage but it should be small). If you don't have a source for air then you can use the mark 1 air compressor other wise known as your lungs. Just blow into the valve while flipping the rotor open and close. You should get the same results.
If any of this is unclear (I know I am not the worlds most succinct writer) let me know and I will post pics and further explanations.
Sox

nize · nize's Garage

when the isv is removed from the car and disconnected, should it flow air or remain closed?

soxnail · 05-04-2007, 11:38 AM

depends on what position it was in when you turned the power off I think.
Sox

Zero10 · 05-12-2007, 10:07 PM

*still curious about my potentially fuggered ISV*
My ISV is not riding in the rubber mounts, so I can actually remove it from the car without removing the intake manifold. I really appreciate the basic tests above, but I have one stupid question......
Key on, engine off, what position should the valve be oscillating around?

I will also check out the 2 transistors on my board. I expect to disassemble the valve and find that the contacts for the brushes (the armature??) is completely eaten away, but we will see