Speedtoys

Im rather embarassed to say...

My high idle slowly came back.

At a light in drive, the car doesn't TRY to hard to move, it's calmer..my peak idle is maybe 50rpm lower than the 1050 it was before warm, in park.

But cold, its perfect..damned perfect.

Warm, 950-1000rpm idle.

The leaky ISV was part of the problem..not all of it.

928NOOBIE

If the new ICV tests OK and doesn't fix my issue I'm taking it to a trusted shop here in town. Regardless of direction needed I'll keep this thread updated until we are done.

SMTCapeCod

Well, I wanted to get a spare ISV given the NLA status anyway. It's smaller than I remembered. Cost more than the Borg from Pepboys one to get Bosch from a 928 vendor-- Thank You 928 Intl! http://shop.928intl.com/Idle-Stabili...28-606-161-00/The Borg is probably a good bet though. I noticed that some sources cross referenced the application to a number of BMW fitments.
Looked like Standard and Airtek (or similar) brands are still on the mainstream market for less, don't know the odds on that dice roll.

I'd say back to ECU but S/toys eliminated that on his.

Speed- did you have a few full-temp drives before it started to revert?
Did you just pull the center T and work from the back, or did you pull more of the intake/other parts?
Would seem like it ought to have been in the scope of things you worked on.

Though, mine still seems a little intermittent and of varying degrees of intensity. Which is why I think ECU. THat plus the incremental nature of the gain at full hot idle, when it happens.

Anyone tried to check timing yet when this is happening?
What about that whole emissions loop...tubes on switch likely too small...Diverter shouldn't bleed vacuum and its line is too small, I think... already did the splitter to my vacuum can...there's still that air bleeder assembly on the strut bar... Hoses reversed? I dunno..

Cuncur that the worn amateur makes no sense given the key symptoms.

Back to A/C circuit? Voodoo curse? Getting old whatever it is. Mechanical obstruction is interesting. Too mired in motorcycle & boat projects at the moment though, Call my Phaedrus, hit the hadit wall with the 928. Let the flogging commence/caretaker status only. More work slated for probably August....

ROG100

Practically all gone - Bosch that is - I have one left.
Same for the 87 to 95.
Porsche has them but Oh My!!! Big $$$

928NOOBIE

Not sure on A/C circuit..I know when I use my AC it doesn't raise it that high. I'm discounting my LH and EZF since KillaV is having same issue and he's running non-Porkenized and is also having same headaches as us. Also since it's only happening when warm and mine gets worse the hotter the engine gets..doesn't feel like computer to me...and no change in Ohms to Idle/WOT pins on LH hot or cold...so harness is working fine there. Mine isn't incremental per se...but I do notice that when driving highway speed and things are cooler in the engine compartment, idle will be helped some...not completely..but some...until things heat up again..

My charcoal cannister vacuum actuator is disconnected, likewise vacuum to/from thermal adaptor...I'm running a pared down system so at least mine can't include those. I yanked all that stuff chasing this down and am going to leave it that way until I get this resolved...then slowly add stuff back..not really concerned with that stuff except maybe the charcoal cannister thing.

Also don't have belt on air pump...

I'll have my ICV Monday and you can bet it's going on the same day...I'll report back

Speedtoys

We pulled all of the intake sections, T and all. Left the throttle body assy in the valley, and checked all hoses and clamps.

It may have been a few drives, but..Bill and I kinda sorta saw it come back right away we think, just _less severe_.

I can see 950-1000 rpm hot now. Not 1050-1100.

If I press REALLY REALLY HARD on the throttle lever..it will go down maybe 25rpm..but that's an unreasonable amount of force. Never did look at the throttle plate stop screw setting. We thought we 'had it'.

SMTCapeCod

That was all helpful in terms of (potentially) eliminating some candidate systems/parts. I'm not optimistic on the ICV- but I'll keep my fingers crossed. If you could, like speedT, maybe check both for flow closed while they are handy to see whether they are the same or different?

Starting to wonder what hard parts would have the clearance to twist/leak while hot. I wouldn't think cam covers would leak that much air, absent a massive accompanying oil leak. Weak seals on the vents that allow air to pass once warm probably would've been encountered by others in the past. The few instances of un-flat intake runners -- well that seems so uncommon and unlikely that they would like while hot.

Were folks' smoke tests done hot?

SMTCapeCod

Bummer, was hoping there might be a shortcut there. I did the ICV with the intake on once before, long time ago, but not the TB. Full intake pull/refresh put the car down for a couple days for me last time, not good (DD).


Bummer, sounds like back to that Mike Frye thread. But Noob did work on the TB too, right? So was that not a factor there?
Just trying to do some elimination across the various attempts, even thought its still conceivable that one or more of us have different problems...seems likely to me that two or more have the same one.

depami

I'd be inclined to try factory chips and see if symptoms change.

ROG100

Killav is using stock chips and has the same/similar issue.

SMTCapeCod

Wonder if we could just unplug it and go for a drive. Would that cause other electrical faults/interuptions?

928NOOBIE

If the leak is the valve in the ICV failing to close properly you won't see the leak by any vacuum test...I noticed today my idle going up and down fairly noticably after I started it when it was good and hot..that's a classic symptom of an ICV responding improperly to signal...running "sluggishly"...that's an immediate replacement candidate by that alone.

I drove my car today like I stole it and it moved as good today if not better than it ever has...

Also...I've got a whistle sometimes..light one...not constant...in my mind the scenario is that engine rpm is going down ....close to where ICV will open but it's closed right now....as engine rpm decreases and it begins to thirst for air...that whistle comes...then ICV opens...sound goes away and I get the rpm "bounce" we see sometimes.

I am almost positive my ICV is at least failing if nothing else at least from perspective of its inability to move correctly when signaled..today was solid proof for me...even though it tested perfectly on my bench...but with the pressures that could be in there...and things expanding with heat..that ICV has to be able to restrict air with 17 inches of vacuum acting against it...plus with that small opening we would have air velocity and pressure...I am having more trouble believing all of us have external vacuum leaks that all just happen to be expressing themselves exactly the same...and am thinking that maybe there's a common component failure that's causing it...just thinking out loud..but you have to admit..look at the odds is all...

I'm leaning more and more in direction of failing ICV.

Speedtoys

Keep up the good work.

I wont be able to at home and "blow" through my KNOWN good pair of S4 ISVs, to compare that to what I could blow thru the "good" old ISV on the 85 now.

The new ISV, was human breathable when closed.

SMTCapeCod

Well good to get that done then.
There is a thread by a lister that chased a whistle, found that the new hose he installed on the ICV was collapsing under big vacuum signals. He reverted to the old hose, IIRC.
He did not note a change in idle, as S/T did when he pinched it.

depami

How does the idle speed adjuster system work? Does it simply regulate air to obtain target RPM? If so, wouldn’t it attempt to compensate for high RPM due to vacuum leaks?

That being said, is it possible to measure ICV input signal? If it has command but no effect, it could be defective. If it has no command, then something else could be driving the high idle.