Stall when returning to idle
03-18-2008 | 04:54 AM
#17
Rennlist Member
Joined: Jun 2001
Posts: 9,714
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From: Barcelona
In a warm climate, like FL, you can get away with removing the ISV. It's a nice feature to have though, as it stabilizes the idle when the engine is cold. Definitely necessary in cold climates.
This doesn't bypass the ISV, which is the only way you can set the idle properly when it won't hold.
This doesn't bypass the ISV, which is the only way you can set the idle properly when it won't hold.
03-18-2008 | 05:55 AM
#18
Drifting
Joined: Mar 2007
Posts: 2,285
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From: Kansas City
Yea, but I wonder if I'll be alright. My car is kept in a climate controlled garage year round, and never sits long enough outside in the winter, to get completely cold.
To bypass it, you just connect the hoses together that the ISV connects to, right? Or do I need to cap both of these off?
To bypass it, you just connect the hoses together that the ISV connects to, right? Or do I need to cap both of these off?
03-18-2008 | 02:27 PM
#19
Three Wheelin'
Joined: Jun 2003
Posts: 1,854
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From: Phoenix, Az
In a warm climate, like FL, you can get away with removing the ISV. It's a nice feature to have though, as it stabilizes the idle when the engine is cold. Definitely necessary in cold climates.
This doesn't bypass the ISV, which is the only way you can set the idle properly when it won't hold.
This doesn't bypass the ISV, which is the only way you can set the idle properly when it won't hold.
it was recommecded by by a shop owner that owns and maintains p-cars, jags, bmw's, mercedes, other foreign stuff as a warranty repair center, as there are no mercedes, porsche, land rover dealers on maui and it appeared he knew what he was talking about.
87951
03-18-2008 | 02:54 PM
#20
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Joined: Oct 2004
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From: Hoosierville
To bypass it, you just connect the hoses together that the ISV connects to, right? Or do I need to cap both of these off?
FWIW I purchased a rebuilt ISV from 944 online for a more reasonable price than a new one. Have yet to install it, but I was having stalling issues as well. Used Tim's smokinator to find the leaks which worked better for me than compressed air alone. With just comp. air I could hear the leak, but was having trouble locating it.
03-18-2008 | 08:51 PM
#22
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From: Barcelona
From the Factory Workshop Manual Turbo Supplement:
24.7. - IDLE ADJUSTMENTS
Note:
Requirements for adjustments:
Engine in perfect mechanical condition. All electric equipment switched off during duration of adjustment. Adjustments must be made as quickly as possible to avoid excess heat in intake ports which would lead to incorrect CO levels. Ambient temperature: 15 to 35ºC/59 to 95ºF.
4. Check and, if necessary, adjust engine idle speed. This requires stopping the operation of the idle speed charging control [ISV].
a. Jumper round female plugs B and C on diagnosis socket with a wire lead. This stops operation of the idle charging control.
b. Instead of a wire lead, Special Tool 9246 (test relay) can also be used. The idle charging control is out of operation when the green test lamp lights up.
5. Turn control screw (bypass) on throttle housing until specified speed of 840 +/- 40 rpm is reached.
6. Restore operation of idle charging control after finishing adjustments by removing wire lead or test relay from diagnostic socket.
Note:
Requirements for adjustments:
Engine in perfect mechanical condition. All electric equipment switched off during duration of adjustment. Adjustments must be made as quickly as possible to avoid excess heat in intake ports which would lead to incorrect CO levels. Ambient temperature: 15 to 35ºC/59 to 95ºF.
4. Check and, if necessary, adjust engine idle speed. This requires stopping the operation of the idle speed charging control [ISV].
a. Jumper round female plugs B and C on diagnosis socket with a wire lead. This stops operation of the idle charging control.
b. Instead of a wire lead, Special Tool 9246 (test relay) can also be used. The idle charging control is out of operation when the green test lamp lights up.
5. Turn control screw (bypass) on throttle housing until specified speed of 840 +/- 40 rpm is reached.
6. Restore operation of idle charging control after finishing adjustments by removing wire lead or test relay from diagnostic socket.
03-18-2008 | 09:10 PM
#23
Drifting
Joined: Aug 2005
Posts: 2,405
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From: SFL
Can you just remove the ISV altogether? Or...is LFA being sarcastic? How does this affect overall drivability? My car has always died following abrupt throttle release from higher RPM's. I have long suspected my APE chips and MAF are responsible for this problem, but I'm about to rule that out (have a new Vitesse kit in my garage now).
03-18-2008 | 10:14 PM
#24
Three Wheelin'
Joined: Jun 2003
Posts: 1,854
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From: Phoenix, Az
This is not correct. It's one thing to make minor adjustments to the idle with the throttle body screw, and another to properly set the idle.
From the Factory Workshop Manual Turbo Supplement:
Like I said, to properly set the idle, you must bypass the ISV. This is done by jumpering ports B and C in the diagnostic socket with the engine at normal operating temperature. Other adjustments from the throttle body screw are just guesswork.
From the Factory Workshop Manual Turbo Supplement:
Like I said, to properly set the idle, you must bypass the ISV. This is done by jumpering ports B and C in the diagnostic socket with the engine at normal operating temperature. Other adjustments from the throttle body screw are just guesswork.
it's been 8 months and i haven't touched it.
the manual:
there was a post here not to long ago about r&r ing the vr without removing everything in the manual so just cuz it's in the manual, there might be a workaround.
87951
03-18-2008 | 10:28 PM
#25
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From: Barcelona
If your ISV or vacuum system ever springs a leak and you try getting your idle back with only the throttle screw, you'll understand what the manual is talking about.
03-19-2008 | 05:12 AM
#27
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Joined: Jun 2001
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From: Barcelona
If your car already holds an idle and you want to make minor adjustments to it by turning the throttle screw, that's your prerogative, but this won't fix the problem in the initial post.
03-20-2008 | 02:39 PM
#28
Three Wheelin'
Joined: Jun 2003
Posts: 1,854
Likes: 0
From: Phoenix, Az
This is beside the point. The reason for this thread is that Keith's car will not hold an idle. The idle is set by the process outlined in the Factory Manual, bypassing the ISV.
If your car already holds an idle and you want to make minor adjustments to it by turning the throttle screw, that's your prerogative, but this won't fix the problem in the initial post.
If your car already holds an idle and you want to make minor adjustments to it by turning the throttle screw, that's your prerogative, but this won't fix the problem in the initial post.
i had the same problem of the idle dropping low but not dying, that's when i made the adjustment, to eliminate the big drop in rpm and using the screw increased rpm and eliminated the big drop in rpm.
87951
03-22-2008 | 01:08 AM
#29
Thread Starter
Nordschleife Master
Joined: Sep 2005
Posts: 5,107
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From: San Francisco
UPDATE
I reset the idle the other night.
When I jumpered the ports and the ISV shut down the engine got really quiet, however the RPM was not that low.
Took me a while to get it right as the car chose to be rich at idle while I was setting it. It seemed to have worked immediately. The RPM still dips down a little bit but its really not that much. Also, when the RPM is falling it now slows down around 1200rpm, didn't do this before but I guess this is correct. The real test was the next morning when I started the car cold. It dipped a small amount but its 80% better than it was.
Thanks Guys!
When I jumpered the ports and the ISV shut down the engine got really quiet, however the RPM was not that low.
Took me a while to get it right as the car chose to be rich at idle while I was setting it. It seemed to have worked immediately. The RPM still dips down a little bit but its really not that much. Also, when the RPM is falling it now slows down around 1200rpm, didn't do this before but I guess this is correct. The real test was the next morning when I started the car cold. It dipped a small amount but its 80% better than it was.
Thanks Guys!
