The ISV modification for LWF
Race Car
Joined: Nov 2011
Posts: 4,356
Likes: 49
From: Cape Town, RSA & Sarasota FL
Hmmm - I just did this.. Today....
Remove the ISV and scribe the metal and the grey plastic so you can get back to the original setting...
Next - take a sharp SMALL jewelers screwdriver, and remove the epoxy from the 3 holes you'll see. Under the epoxy are 3 allen screw heads. Clean enough epoxy so you can get to the screws.
Next - loosen the screws a bit, and turn the plastic part (the electrical connector) about 3 degrees COUNTER CLOCKWISE.
Next - tighten one screw head so nothing moves.
Next - reinstall the ISV and start the car.
Next - if the idle isn't right (mine is set at 890) - loosen that one screw head, and turn the base (the grey part that the electrical connector is molded into) about 1 degree. Let the engine settle.
Next - repeat the previous step as needed. If you go too far - turn it back, and start over - the ISVs are VERY sensitive as is the idle as you adjust it...
Next - when you are set - tighten all three heads.
JOhn
Remove the ISV and scribe the metal and the grey plastic so you can get back to the original setting...
Next - take a sharp SMALL jewelers screwdriver, and remove the epoxy from the 3 holes you'll see. Under the epoxy are 3 allen screw heads. Clean enough epoxy so you can get to the screws.
Next - loosen the screws a bit, and turn the plastic part (the electrical connector) about 3 degrees COUNTER CLOCKWISE.
Next - tighten one screw head so nothing moves.
Next - reinstall the ISV and start the car.
Next - if the idle isn't right (mine is set at 890) - loosen that one screw head, and turn the base (the grey part that the electrical connector is molded into) about 1 degree. Let the engine settle.
Next - repeat the previous step as needed. If you go too far - turn it back, and start over - the ISVs are VERY sensitive as is the idle as you adjust it...
Next - when you are set - tighten all three heads.
JOhn
Are they on the metal on grey plastic? If so, where exactly please?! pics?
Mine is a 964 isv - maybe that is the problem ie different design ...
but its seems to work on 993's and 911SC per above posts so Ì'd imagine
it shd work on the 964 .... once I find those buried allen heads. TIA!!
if these are the 3 screws ... I'm screwed ... cos my ISV is sealed in comparison and has nothing like those bolts on the plastic/grey side where the plug is.
http://www.type911shop.co.uk/shop/sy...3Dposition1%26
Three Wheelin'
Joined: Jul 2004
Posts: 1,548
Likes: 42
From: FL full time
I could not find the original 993 'ISV adjustment' post that talked about loosening the three screws and turning the plastic connector body counter clockwise to raise the idle speed to prevent stalling at stop lights/signs. I have a TPC Supercharger, light weight flywheel, rebuilt engine that was running very fine for several thousand miles. Recently I was getting repeated stalling at lights, stop signs, slow down shifts. I just did the ISV adjustment, see pix. I did a drive today today that seems to have fixed the stalling issue. My take on this is that the mod gives a softer (slower) landing to the OEM idle speed. The engine does go down to about 800 rpm but only after it drifts down from about 1000 rpm. Bottom line, for me at least, no stalling!!!! The first pix shows the scribe lines back filled with magic marker and approx 1/8" ccw adjustment. The second pix shows hot melt glue I used to lock the screws in position.
Advanced
Joined: Oct 2018
Posts: 54
Likes: 1
Hi,
update regarding this mod
I already have on my car sport camshaft and to avoid stalling when going back to idle, my tuner increase the idle to 950
I will install the RS flywheel and have an ISV ready to do the modification
question is:
does this modification increase a lot the idle rpm ? or it's marginal cause I do not want an idle at 1200 rpm :-)
thanks for your feedback
update regarding this mod
I already have on my car sport camshaft and to avoid stalling when going back to idle, my tuner increase the idle to 950
I will install the RS flywheel and have an ISV ready to do the modification
question is:
does this modification increase a lot the idle rpm ? or it's marginal cause I do not want an idle at 1200 rpm :-)
thanks for your feedback
Rennlist Member
Joined: Aug 2009
Posts: 1,443
Likes: 176
From: Earth
If done properly it does not change idle RPM.
Think of it like adjusting carb butterfly stop. You’re adjusting it in a way that limits the amount the ECU can close the valve by mechanically setting it open wider. In fully closed position it will now let more air in. Not enough so to maintain idle speed let alone high idle. The ECU will still need to pulse it to maintain idle.
What this does is limit the amount the ECU has to “catch” the engine on the way down RPM’s to idle thus helping to prevent stalling.
Think of it like adjusting carb butterfly stop. You’re adjusting it in a way that limits the amount the ECU can close the valve by mechanically setting it open wider. In fully closed position it will now let more air in. Not enough so to maintain idle speed let alone high idle. The ECU will still need to pulse it to maintain idle.
What this does is limit the amount the ECU has to “catch” the engine on the way down RPM’s to idle thus helping to prevent stalling.
Last edited by MarinS4; May 12, 2022 at 12:37 AM.
