porsche 993 ISV
Discussion
hi guys,
as i'm sure most 993 owners are aware there's something on top of our engines called an isv (or idle stabliser valve) that can cause a few owners some problems, nothing too serious but annoying all the same. the bulk of the problems revolve around, yes you guessed it the engines idle speed. basically this little bit of kit keeps engine revs where they should be regardless of engine/ambient temperatures & presures by way of a motor operated valve.
the problems mainly result in a hunting idle speed, but can manifest in other ways such as a slow return to idle from high revs, stalling, jerkiness in traffic & mild to more noticeable "kangarooing".
basically small amounts of debris,soot & oil gets into the mechanism & this gradually hinders the operation of the valve. the problems usually don't become immediatly apparent due to the fact that the fault only gets worse little by little, so you may not even realise there is much of a problem because it's not like a part suddenly failing.
my car seemed to show signs of something wrong after its winter lay up, a italian tune up appeared to solve it but i thought i'd investigate when i had the chance.
now, there are a few guides on this out there on the usual sites (jackals, pelican, renn list, 911uk etc) but like a lot of owners the thought of taking bits off the engine of my p&j can be a little nerve wracking to say the least so i thought i'd post this up to show you it's so simple, even a hairdresser can do it! you probably won't need much more than a 7mm socket, a screwdriver & some rubber freindly lube (;)) but things can be a little more akward so take a couple of minutes to have a look at yours & decide from there....
so, here we are with the valve in place on top of the engine, its the cylindrical part about 5 inch long (perhaps get the missus to measure if you're not sure
) with a rubber hose attatched to the rear & a aluminium u shaped pipe attatched to the front by way of a rubber connector. the first thing to check is where the screw heads are on the worm drive hose clips. you need to be able to access all three (two front, one rear) so if yours have been left facing down by some helpful Herr at the factory make sure you have a flexi connection for your 7mm socket set so you can do it, this may be the only part that you find tricky, if they're all within easy reach you're on.
first job is to unplug the electrical connector on the left side, just push the metal clip in & it pops off. then undo all three worm drive clips on the hoses (the jubilee clips), i didn't bother undoing them fully as the metal part gives you something useful to push against.
next, i found it easier to pull the aluminium u tube out of the front first as this was easiest to grab hold of & get some purchase on, the rubber connector that has the two clips on can then be popped out to give yourself some more room, the aluminium u shaped tube has a fair bit of play but i didn't want to cause any headaches so i was just happy enough holding it out of the way
after this, you need to get the rear hose off, i suspect everyones is different but after undoing the clip i found you coud pull the isv itself forward a quarter of an inch & then using a spanner, leaver the rear hose off. mine came away quite easily but then i reckon the valves been out before to be cleaned, yours may take a bit more elbow grease.
once that's out of the way you just need to slide the isv out of its mounting bracket by pushing it to the right, i found when mine popped out the rubber o ring that supports it came away as well but this only makes things easier. then simply remove all the clips so they don't fall down the back & you're ready to get cleaning.
see the dirt? not much eh, but like i said i suspect mine has been cleaned before. now, all the guides describe how the valve can be heard moving around but even with that little amount of dirt in there mine didn't make a sound, not good! see some of the other thraeds on this & you can see all types of oil & crap in there but mine just looked a little sooted up. basically i sat mine in a jug of white spirits overnight, making sure to keep the electrical connector end dry. one tip, unless your missus likes the smell of white spirits leave it in the garage-oh & don't use her best measuring jug! this one was just the right size so it couldn't fall over inside it & get soaked.
if you're anything like me you won't be able to just leave it there so i went back after a couple of hours & it had totally freed itself up. if you hold the cylinder part of the isv like a door knob & twist it quickly back & forth you can hear the valve opening & closing-it's quite loud. then get it there with some cotton wool buds & get it totally cleaned, it should come up like new, i then left it overnight to soak fully & was lft with this:
![](http://thumbsnap.com/sc/jFqGgscI.jpg[/img]</a> <a href="http://thumbsnap.com/V7N9k1dj" Target="_blank">[img]http://thumbsnap.com/sc/V7N9k1dj.jpg)
nice eh?! a good final clean out with some kitchen roll & then i left it for the rest of the day to dry out:
clean enough for a 911uk member!(well nearly
)
the fitting of it all is obviously the reverse of taking it off, remember, plumbers & pipe fitters are careful of what lube they use as some detergents can erode rubber so like i said use something gentle, if nothing else you've got an excuse for buying some & what you use the left overs for is entirely up to yourself! i greased up the rubber o ring on the actual isv mounting as this helped it slide back in but you may feel you don't need to.
my car when fired up for the first time had an erratic adle for around 10 seconds until it seemed to reset itself & then it was fine. also, some people advise leaving the battery disconnected while you do this job so that the dme resets itself & starts afresh with its ecu "learning". now, i don't know about this but i figured why not, just remember your alarm key as it tends to set it off when you disconnect the electric. if you don't do this don't forget to shut the engine lid over night as the light in there can drain the battery pretty quick if left on.
i think thats about it? hope this helps anyone nervous of having a go, all in certainly no more than 45 mins to take it off & half an hour to put it back on.
craig
as i'm sure most 993 owners are aware there's something on top of our engines called an isv (or idle stabliser valve) that can cause a few owners some problems, nothing too serious but annoying all the same. the bulk of the problems revolve around, yes you guessed it the engines idle speed. basically this little bit of kit keeps engine revs where they should be regardless of engine/ambient temperatures & presures by way of a motor operated valve.
the problems mainly result in a hunting idle speed, but can manifest in other ways such as a slow return to idle from high revs, stalling, jerkiness in traffic & mild to more noticeable "kangarooing".
basically small amounts of debris,soot & oil gets into the mechanism & this gradually hinders the operation of the valve. the problems usually don't become immediatly apparent due to the fact that the fault only gets worse little by little, so you may not even realise there is much of a problem because it's not like a part suddenly failing.
my car seemed to show signs of something wrong after its winter lay up, a italian tune up appeared to solve it but i thought i'd investigate when i had the chance.
now, there are a few guides on this out there on the usual sites (jackals, pelican, renn list, 911uk etc) but like a lot of owners the thought of taking bits off the engine of my p&j can be a little nerve wracking to say the least so i thought i'd post this up to show you it's so simple, even a hairdresser can do it! you probably won't need much more than a 7mm socket, a screwdriver & some rubber freindly lube (;)) but things can be a little more akward so take a couple of minutes to have a look at yours & decide from there....
so, here we are with the valve in place on top of the engine, its the cylindrical part about 5 inch long (perhaps get the missus to measure if you're not sure
) with a rubber hose attatched to the rear & a aluminium u shaped pipe attatched to the front by way of a rubber connector. the first thing to check is where the screw heads are on the worm drive hose clips. you need to be able to access all three (two front, one rear) so if yours have been left facing down by some helpful Herr at the factory make sure you have a flexi connection for your 7mm socket set so you can do it, this may be the only part that you find tricky, if they're all within easy reach you're on.first job is to unplug the electrical connector on the left side, just push the metal clip in & it pops off. then undo all three worm drive clips on the hoses (the jubilee clips), i didn't bother undoing them fully as the metal part gives you something useful to push against.
next, i found it easier to pull the aluminium u tube out of the front first as this was easiest to grab hold of & get some purchase on, the rubber connector that has the two clips on can then be popped out to give yourself some more room, the aluminium u shaped tube has a fair bit of play but i didn't want to cause any headaches so i was just happy enough holding it out of the way
after this, you need to get the rear hose off, i suspect everyones is different but after undoing the clip i found you coud pull the isv itself forward a quarter of an inch & then using a spanner, leaver the rear hose off. mine came away quite easily but then i reckon the valves been out before to be cleaned, yours may take a bit more elbow grease.
once that's out of the way you just need to slide the isv out of its mounting bracket by pushing it to the right, i found when mine popped out the rubber o ring that supports it came away as well but this only makes things easier. then simply remove all the clips so they don't fall down the back & you're ready to get cleaning.
see the dirt? not much eh, but like i said i suspect mine has been cleaned before. now, all the guides describe how the valve can be heard moving around but even with that little amount of dirt in there mine didn't make a sound, not good! see some of the other thraeds on this & you can see all types of oil & crap in there but mine just looked a little sooted up. basically i sat mine in a jug of white spirits overnight, making sure to keep the electrical connector end dry. one tip, unless your missus likes the smell of white spirits leave it in the garage-oh & don't use her best measuring jug! this one was just the right size so it couldn't fall over inside it & get soaked.
if you're anything like me you won't be able to just leave it there so i went back after a couple of hours & it had totally freed itself up. if you hold the cylinder part of the isv like a door knob & twist it quickly back & forth you can hear the valve opening & closing-it's quite loud. then get it there with some cotton wool buds & get it totally cleaned, it should come up like new, i then left it overnight to soak fully & was lft with this:
nice eh?! a good final clean out with some kitchen roll & then i left it for the rest of the day to dry out:
clean enough for a 911uk member!(well nearly
)the fitting of it all is obviously the reverse of taking it off, remember, plumbers & pipe fitters are careful of what lube they use as some detergents can erode rubber so like i said use something gentle, if nothing else you've got an excuse for buying some & what you use the left overs for is entirely up to yourself! i greased up the rubber o ring on the actual isv mounting as this helped it slide back in but you may feel you don't need to.
my car when fired up for the first time had an erratic adle for around 10 seconds until it seemed to reset itself & then it was fine. also, some people advise leaving the battery disconnected while you do this job so that the dme resets itself & starts afresh with its ecu "learning". now, i don't know about this but i figured why not, just remember your alarm key as it tends to set it off when you disconnect the electric. if you don't do this don't forget to shut the engine lid over night as the light in there can drain the battery pretty quick if left on.
i think thats about it? hope this helps anyone nervous of having a go, all in certainly no more than 45 mins to take it off & half an hour to put it back on.
craig
Well, even though mine was stuck fast I didn't seem to have many of the problems other people have, mine was just a bit lazy in returning to idle speed after being revved. However, that's disapeared so it would seem that was the problem, it was also jerky in traffic after being laid up over winter, I described it as like the throttle being an on off switch & that's now gone, although to be fair after a good run that seemed to disapear anyway.
Still it's nice to know it's all dine & cleaned now.
Still it's nice to know it's all dine & cleaned now.
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