Should ISV turn manually??

dlpalumbo · 07-01-2009, 05:44 PM

I've tried cleaning my ISV, but I still have idle problems. A new O2 sensor helped a lot, but the idle still bounces when I depress the clutch.

I took off ISV (again) and tried to rotate the valve. I didn't apply much pressure, but it seemed to be stuck. It was open about 1.5mm.

Is this normal??

Thanks,

Dan

Steven C. · 07-01-2009, 07:15 PM

You should be able to turn it once it is clean. Apply 12v to it and see if it turns. If not it needs to be cleaned with WD40 or carb cleaner and a Qtip.

1990-964 · 07-01-2009, 09:38 PM

Quote:

Originally Posted by dlpalumbo

I've tried cleaning my ISV, but I still have idle problems. A new O2 sensor helped a lot, but the idle still bounces when I depress the clutch.

I took off ISV (again) and tried to rotate the valve. I didn't apply much pressure, but it seemed to be stuck. It was open about 1.5mm.

Is this normal??

Thanks,

Dan

This may be unrelated but I had been recently having idle problems too. In my case the car would not hold an idle reliably with the isv connected. Even when it would idle it would hunt too much. I tried many things, cleaning the isv, swapping it out for a different unit, cleaning the DME connector pins thinking it could be resistance related and none of it worked. When the isv was disconected it would idle fine except when cold so in frustration I hooked up a bypass switch to the isv so I could control it from the cabin as needed. This got me by but I knew there must be a fix. A mechanic that I know who works on my neighbors Porsche's suggested that the throttle body/AFM was dirty and cleaning it would likely cure the problem. With some skepticism I let him do the work and it worked like a charm. It now idles just as it should with a rock steady idle whether the A/C is on or not. All this and I have a LWF and no harmonic dampener with serpentine alternator belt. So if this can get my car running right it may be worth a try. If you do it yourself it is free and only takes about an hour or less.

dfinnegan · 07-01-2009, 11:14 PM

Note that the ISV valve turns the opposite way that you might think!

When you look into the valve you can see a gap, that gap must close, then the valve moves past and opens on the other side. Others have broken these valves by trying to make push the valve the wrong way.

If you hold the body in your hands as you might a pencil with both palms facing each other and roll it quickly back and forth you should hear the valve clicking as it swings from side to side.

DaveK · 07-02-2009, 09:45 AM

"Bouncing" idle is exactly what mine did when the dist caps were worn.

68CGPlt · 07-02-2009, 03:33 PM

I had the same experience as DaveK. Cleaned ISV, replaced O2 all of which helped some, however Dist caps and rotors were the fix.

TR6 · 07-02-2009, 04:24 PM

Quote:

Originally Posted by dfinnegan

Note that the ISV valve turns the opposite way that you might think!

When you look into the valve you can see a gap, that gap must close, then the valve moves past and opens on the other side. Others have broken these valves by trying to make push the valve the wrong way.

If you hold the body in your hands as you might a pencil with both palms facing each other and roll it quickly back and forth you should hear the valve clicking as it swings from side to side.

I broke my ISV exactly as described above. The only consolation was that I now have a brand new ISV.

07-01-2009, 05:44 PM	#1
dlpalumbo User Join Date: Nov 2007 Posts: 7	Should ISV turn manually?? I've tried cleaning my ISV, but I still have idle problems. A new O2 sensor helped a lot, but the idle still bounces when I depress the clutch. I took off ISV (again) and tried to rotate the valve. I didn't apply much pressure, but it seemed to be stuck. It was open about 1.5mm. Is this normal?? Thanks, Dan

07-01-2009, 07:15 PM	#2
Steven C. Addict Rennlist Member Join Date: Aug 2005 Location: Dallas, TX Posts: 1,614	You should be able to turn it once it is clean. Apply 12v to it and see if it turns. If not it needs to be cleaned with WD40 or carb cleaner and a Qtip. __________________ Steve 02 996C2 daily driver 91 964 turbo...I'm baack! 71 Fiat Vintage Racer it's red too. 4th owner. 68 Alfa GTAM Replica Vintage Racer....what? Ok it's RED. ''Aerodynamics is for people who can't build engines"- Enzo Ferrari "Back in my day, tires were skinny and the drivers were fat"- Fangio "I don't have time to read gauges, I'm racing!" M Andretti www.firebreathingfiats.com www.corinthianvintagerace.com [IMG][IMG]

07-01-2009, 11:14 PM	#4
dfinnegan Addict Rennlist Member Join Date: Jul 2005 Location: NY, USA Posts: 2,908	Note that the ISV valve turns the opposite way that you might think! When you look into the valve you can see a gap, that gap must close, then the valve moves past and opens on the other side. Others have broken these valves by trying to make push the valve the wrong way. If you hold the body in your hands as you might a pencil with both palms facing each other and roll it quickly back and forth you should hear the valve clicking as it swings from side to side. __________________ 1991 C4 Coupe, Polar Silver The hours a Porsche spends parked. You don't get those back.

07-02-2009, 09:45 AM	#5
DaveK Addict Rennlist Member Join Date: Nov 2001 Location: Surrey, UK Posts: 3,764	"Bouncing" idle is exactly what mine did when the dist caps were worn. __________________ Dave '90 964 C4 '02 996 TT

07-02-2009, 03:33 PM	#6
68CGPlt Addict Rennlist Member Join Date: Apr 2005 Location: New Jersey Posts: 158	I had the same experience as DaveK. Cleaned ISV, replaced O2 all of which helped some, however Dist caps and rotors were the fix. __________________ 93 RS America 94 Carrera 4 WB Previous P-Car Rides: 03 996 C4S 97 993 C4S 87 944S