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TB thread was turning into ISV discussion, so i thought it best to start another....
I am more than a bit confused on whether to replaced my 28 year, 88k ISV. after taking my intake off, for a second time,
I realized it is not a big deal....however....that being said, I don't want to make a habit of it.
did not replace the ISV the first time out, and thinking to just get it over with this time, but all the threads I have read send very mixed
messages. some say absolutely, while others say, if its working, just clean it up.
I have a minor idle issue, (not surging or hunting, more like "drifting") and feel pretty good that it is the TPS. logic would dictate that age/miles can't be an asset to the ISV.
I would opt for one of roger's lowe units at 70, because the bosch @ 300 is just too much! most seem to be happy with the lowe, but a few have posted that
there have been issues? and I have read more than a few threads about installing new bosch units, that caused issues, forcing folks to reinstall the original?
this might be going down the oil and coolant roads, but curious if there might be a consensus on this one?
Last edited by merchauser; 12-03-2018 at 07:49 PM.
Just remember that the S3 item is going to wear out by design, but the S4+ (like yours, presumably) should not. I don't mean that it should work forever, but it's not the wear item that the one in the S3 is. Based on all the troubles I've had* getting one to "work" properly, if yours is working fine I would leave it alone.
*FWIW, mine is the S3 version, and I haven't proven my idle issue is actually ISV-related, despite my deeply-held belief that it is lol...
I cleaned the ISV on my S4 with WD-40, then followed with electrical parts cleaner (spray)...evaporates almost immediately. Testing with a 9V battery it seemed to work fine before I cleaned it. After I cleaning it seemed to respond more quickly to open and close...but that may have been what I wanted to see. It was a bit dirty inside, but not bad for 30 years old.
Before cleaning After cleaning
Last edited by Captain_Slow; 12-04-2018 at 07:02 AM.
Reason: add photos
When my motor was in its original 90S4 and the kit was about 10 years old I had an idle problem. I was advised that the ISV needed replacing at whatever $$$'s I was quoted. Did not accept that so decided it was time to get my hands dirty and did my first inlet manifold job. When I got to the ISV I found the shuttle was jammed and contaminated with a dry greyish powder. Cleaned the thing best I could until the shuttle was free to move, applied a 9V supply and it opened and closed perfectly. Reinstalled the thing and it gave me good service until I replaced it earlier this year, still functioning but I wanted to try a replacement so installed the Lowe unit that works exactly the same. I view the original unit as a viable spare and it has about 100k miles under its belt. I dare say as with all things it will fail eventually but they do a seem to be a very robust items that needs a clean every now and then- about every 10 years in my case.
If the thing has served for 10 years I take the view it owes its owner nothing.
Last edited by FredR; 12-04-2018 at 10:41 AM.
Reason: typing errors corrected
I replace every one of them when I have the intake off for the first time. I also use both the Bosch and Lowe and have yet to see a failure. One of our more vocal members touted how his Lowe unit was bad and pitched a fit about it so Roger took it back, I've had that same one on my car for 2 years now.
Just like the flappy actuator, it can function perfectly right up until the moment it doesn't. Just replace it and move on. Nothing is more annoying than a tested flappy actuator failing within weeks of refreshing the intake. BTDT.
The ISV is not a binary device. It’s fed a pulsed signal from the LH with the duty cycle of the signal determining the average air-pass-through opening size. It operates in closed loop with the o2 and mass-air sensor.
If the ISV gets sticky the resulting actuation delay will cause the control loop to mis-behave. Weird idle problems may follow depending upon how sticky.
Has anyone ever found a dead-dead-dead S4+ ISV? Not dirty. Not sticky. But, a fairly clean not-used-in-the-desert-storms (like Fred’s) ISV that was electrically dead when bench tested?
The ISV is not a binary device. It’s fed a pulsed signal from the LH with the duty cycle of the signal determining the average air-pass-through opening size. It operates in closed loop with the o2 and mass-air sensor.
If the ISV gets sticky the resulting actuation delay will cause the control loop to mis-behave. Weird idle problems may follow depending upon how sticky.
Has anyone ever found a dead-dead-dead S4+ ISV? Not dirty. Not sticky. But, a fairly clean not-used-in-the-desert-storms (like Fred’s) ISV that was electrically dead when bench tested?
Anyone? Anyone? Bueller?
A few, which were so gummed up and dirty they could not be saved. No matter how much I tried to clean them up. I cringe every time I see someone recommend spraying WD-40 in the intake hoses. Complete waste of time as if the fluid even gets close to the ISV, it's just going to gum it all up. So it may give you a bit of time, it sure isn't going to fix the issue. You are more likely getting that fluid in the throttle body and sucked up in to the intake than it actually getting to the ISV.
A few, which were so gummed up and dirty they could not be saved. No matter how much I tried to clean them up.
Right. This I get. So far I haven’t had a ISV in my hands that had been used to pass gum. If I found one that way I would absolutely replace it and wouldn’t even bother trying to clean it.
Hence my question: electrically dead and not totally gummed-up?
Or, has anyone bench-cleaned an ISV and then later had it die electrically in service?
I cringe every time I see someone recommend spraying WD-40 in the intake hoses.
WD-40 is The Devil’s Fluid. It has a few uses. But this isn’t one of them. It needs to stay far away from an ISV even if the ISV is on the bench.
Complete waste of time as if the fluid even gets close to the ISV, it's just going to gum it all up. So it may give you a bit of time, it sure isn't going to fix the issue. You are more likely getting that fluid in the throttle body and sucked up in to the intake than it actually getting to the ISV.
Totally agree. But we’re talking bench-cleaning here.
The ISV is not a binary device. It’s fed a pulsed signal from the LH with the duty cycle of the signal determining the average air-pass-through opening size. It operates in closed loop with the o2 and mass-air sensor.
If the ISV gets sticky the resulting actuation delay will cause the control loop to mis-behave. Weird idle problems may follow depending upon how sticky.
Has anyone ever found a dead-dead-dead S4+ ISV? Not dirty. Not sticky. But, a fairly clean not-used-in-the-desert-storms (like Fred’s) ISV that was electrically dead when bench tested?
Dave,
The last thing I would do in a Shammal [desert storm] is go for a drive in any car I owned- they can fetch the paint off the front of the car and etch the headlamps in minutes. Many years ago when working in Riyadh we were advised one day to go home early. Our office was next to the military airport and as I skirted the perimeter a C130 Hercules was coming in to land- as he came over my head his engines revved up and off he went again. As I looked over my shoulder I could see why he scarpered- the storm was about to hit the airfield. I scampered home as quickly as I could with the storm chasing me- it was just like that scene in the Mission Impossible movie shot in Dubai- very scary. On the oil fields we were advised that if we got caught out in such to just stop the car and sit it out.
Ironically despite the environment I have never seen any signs of dust ingress in my motors and the engines generally last very well as they never see cold starts.
Fully agree with your comments about the ISV. I cleaned mine with a cotton cloth and when I got as much out as I could I squirted some carb cleaner into the thing- did not have an air gun at the time to blast it.
The Lowe item seems to be so well made I would not be at all surprised if it is that company who makes the ISV for Bosch and doubles the cost to put it in a Bosch box who in turn double the cost to put it in a Porsche box. How many different cars use this model of ISV would be interesting to know. The Lowe item is surely cheapish but it does not look like a cheap knock off - far from it in fact if superficial looks are anything to go by. Fully appreciate the dilemma you professional chaps face given your need to warrant your work and your time to change out these things is likely way more than the value of the Lowe part and probably the OEM Bosch part.
I also do not like the idea of squirting WD40 into the ISV.
12-03-2018, 06:02 PM
Replace ISV as wear/age item or not?
