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OK, so I have my replacement part (thanks Roger!) and I'm ready to dig in...unfortunately, I haven't found any write-up of this job that doesn't also include an entire top-end refresh. However, I've seen numerous references to being able to do this without removing the intake on an S3. I imagine I need to remove the PS "intake box thing" from the intake tubes...once I do that, is it obvious what I need to do?
Pretty obvious, but fiddly unless you have really small hands.
It can be done, there are various surgical approaches.
I took off the throttle plenum in addition to the side boxes.
I'd have to recommend against it. I've done it, but only after having practiced once with the entire intake manifold and fuel rails removed. And I did it after my hoses had recently been replaced. if your hoses are old and hardened it's going to be extremely difficult to pull them off without damaging other things under the manifold. You'll bust the hell out of your knuckles at the very least. At worst it will simply be impossible to get enough leverage. At least see if your hands are too big before you proceed. My average size hands just barely fit under there.
If I pull the intake runners, I have to replace the gaskets, etc right? But the center T fits into the throttle body so I guess I wouldn't have to in that case. I can fit my hand in from the back, with the airbox out of the way, and feel what I think is the ISV, but I can't see it when I do that. Sticking my camera in there, I see this:
I think that's it, but...what is that clamp around the body? It doesn't appear to be clamped TO anything...I can move it around a bit.
I'll look into that center T. As it is, I can get one (only one) hand in there, and only then while blind. Really didn't want to deal with intake runners and fuel rails, but I always have to be wary of urges to shortcut past the removal of things in the way in order to save time...which invariably does NOT save anything.
OK, moving the T out of the way was a huge help. Then with a long extension and a universal joint on the end I was pretty easily able to loosen the hose clamps (btw, that clamp on the body does appear to be holding the ISV to something, I'm just not sure what...it's not the block, because the whole thing moves around a little). Those hoses though, are now the problem. They don't actually feel too crispy, but they're definitely baked onto the ISV barbs pretty well. I was hoping to save the electrical connector with that stupid wire retainer for last, but we'll see...
Yeah, if you pull the runners, you have to pull the fuel rails and replace the manifold gaskets. It's not too difficult. Just time consuming. However, getting the "T" out is a tight fit without pulling the runners. It just barely has room to come out on my car. That clamp just attaches to a metal tab that just holds it in place. It might be somewhat flexible.
At least for the purposes of accessing the clamps on the ISV, I found I don't really need to get it all the way out. I just loosened the top hose clamp connecting it to the throttle body and pulled it up until it caught on the other runners. I can see (sort of) and reach most everything now, if only these...damn...hoses...will come off....
Well. I managed to get the old one out, and the new one in, and everything back together. Yay, me. The problem is, none of the things I was trying to fix, are fixed. The tendency for RPMs to dip almost to 0 if you put the clutch in and brake for a stop with the RPMs around 3K or higher (sometimes resulting in a stall)...still there. My high idle...even higher. Like, 13-1500 RPMs now.
It is entirely possible that I've introduced a vacuum leak(s) while doing this job. I had a bit of a time getting the intake runner and throttle-to-T hose clamps tightened up without the little hose couplings slipping off one end, etc. And that hose between the T and the outer intake box seem way too short. Not sure what's up with that...
Anyway, long story short...I have confirmed that I can replace an ISV. I have not confirmed that I SHOULD replace the ISV lol...
Well nice job replacing it anyway. Yeah, vacuum leaks definitely cause a high idle. When I had a stalling issue like that, a bad MAF was the culprit.
The ISV change could cause a higher idle too though. They do allow some air to pass even when fully closed, so you might try tightening the idle screw on the throttle body. I would try to fix the stalling issue first, though.
To clarify that...it rarely actually stalls. Usually, the idle drops rapidly and then bounces back up...I became proficient at goosing the gas a bit as it dropped, which would prevent it from dropping past the idle point. Someone suggested that it could be an ISV issue, but then it seemed to get better for a while. So this may not actually be an ISV thing. My MAF is a re-conditioned one from about a year ago that hasn't given me any issues, as far as I know. Generally, the car has been running great, other than these issues.
If the old ISV was sicking (worn out) it could have take out the "driver" circuit in the LH.
Now that you have a new ISV see if you can borrow one to test how it idles.
I have a bad LH on the shelf and it idles at 1300 to 1500 RPM, been down this same road
Hmm, I did a thorough intake refresh (and Porken chip install), and not too long after started getting the same symptoms op is describing - big dip/high rebound after throttle blip and high idle (1100-1200).
Was also assuming a vacuum leak, but now am wondering is this clearly LH symptoms or is that just another possibility, and it could be still be vacuum leaks? Troubleshooting for ISV and circuit first maybe?
I should add, my symptoms also include some cold start up stumbles. I keep the throttle cracked open on cold start or it will surge/bog/die for a few seconds.
FWIW regarding the old ISV taking out the LH driver...the motor in it seemed good, at least it reacted in both directions with a 9V battery. I'm not sure exactly what kills the drivers though...is it a failure of the motor inside to do its thing, or could a leak also have that effect?
05-27-2017, 11:36 AM
ISV/ICV replacement ('86.5)
