[DaveN]

Rock stready so that explains why I couldn't get the idle to vary by squirting volatiles around. I would assume with all the track sand flying that fine dust could make its way to the ICV? I tapped it with a screwdriver but the idle didn't change. Odd that it will idle at about 850 for 30 seconds after starting and then rise and stay at 1100. <acronym title='mass air flow'>MAF</acronym> is sparking clean; first thing I did.

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[MB968]

Seems odd that it will idle at 850 for 30 sec. and then settle in on a higher rpm.



A lot of ECUs increase the idle speed if the A/C is on, or if the engine is cold, decreasing as it warms up, etc. I'm not familiar enough with the 968 yet to know if or when the ECU might increase the rpms and what sensors it uses in its decision making. But, could it be a faulty coolant temp sensor, intake air sensor, or?

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[flash]

yeah- it sounds like a sensor somewhere. does the car run right otherwise?



i'm still not ruling out vacuum, just because i found that you can have a leak in a control circuit, but it not show up on the gauge. what you will have to do is test each and every vacuum hose.



did you check the ICV hose? no kinks?

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[DaveN]

Car runs greeat. I pulled the IVC hose and checked for dirt, etc. Cleaned the hose and squirted <acronym title='mass air flow'>MAF</acronym> cleaner into the hose hoping to have some of it get to the ICV and maybe flush it out a bit. Re-assembled and still settles in at 1100. I may have to wait until I get to my mech's lift to polk around underneath. If I want to pull the ICV I have to dump all the coolant and swear a little (lot) to get my fingers at that rear bolt so I may just wait for the savvy hands of my friend/Porsche mechanic; he has tricks fo rthese things AND a beer fridge.

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[flash]

for the third time, is the hose from the ICV to the 3" elbow in front of the supercharger kinked?

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[DaveN]

I guess I'm always eluding to the answer but never nailing it, NO <img src="/forum/images/smilies/968/wink.png" class="smilie" alt="" />

Just went out to a cold car and pulled the ICV connector and let it warm up, hmmm, straight to 1100 RPM.

Plugged it in and it dropped to 1000, did it a few more times and the car sort of idles at 950-1000 now. I have a feeling I just got so muxh crap in there during that track day that it's clogged. Only way to pull it (nicely) is from underneath so I will let it lie for a few weeks until I get to a lift, remove, and clean the daylights out of it.

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[jfrahm]

I would not be surprised to find a lot of grit in the ICV or gunk from blowby, etc. They are not hard to clean, and you can use a 9v battery to activate them out of the car. There are also lots of replacement options, BMW Saab, Volvo, etc. I recommend getting a replacement and if it is used, clean it very very well and then swap them out. I think the common Bosch 0 280 140 505 part will swap. One of my cars had an old E30 BMW ISV on it which worked fine despite not even having the 90 degree head.



Cheers,

-Joel.

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[DaveN]

Tks for the input. We'll see what's in there when I pull it. I had to wash my engine twice to get all the sand out of the nook and crannies. The K&N looked like it had 200K on it give the amount of dirt and sand that fell from the unit upon cleaning. The ICV is probably very sensitive about any kind of dirt.

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[DaveN]

After tinkering even more I noticed that there is a pressurized whoosh in the middle of the engine bay when I turn off the car; hadn't really noticed it before. Unless you're quick after stopping the engine you can't hear it as it's gone by the time you get your head into the engine bay.

It seemed to be coming from the front of the intake manifold and not from anywhere I would expect the extra pressure from the S/C to bleed.

I have a thermal intake gasket and I fear that the hot track day made it get soft and bulge out causing my idle problem.

Do these gasket not like heat? 968 heat that is <img src="/forum/images/smilies/968/wink.png" class="smilie" alt="" />

Won't know if this is the answer until I get a new gasket and replace it. I won't get the Teflon gasket again if we concur on the failure.

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[banditsc]

The whoosh noise is normal, they all seem to do it, some are just louder then others.

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[tamathumper]

I've noticed the "whoosh" several times, including today, when I had my air filter removed for setting my belt tension.

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[flash]

what the heck are you talking about?

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[Eric_Oz_S2]

Why did you use a thermal intake gasket - what's wrong with the stock paper gasket?

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[tamathumper]

Flash, about one second after turning off the key, there is a loud "decompression" sound from the engine bay, especially noticeable when the air filter hood is removed. Mine has been doing it since I bought it last spring, and I've assumed it is normal. I've been working on the car recently tweaking the belts, so I tend to leave the top down and the hood up, and reach into the car to start and stop it while standing next to the driver's door. Usually you can't get out of the car and up next to the engine in a second, so it's not heard, but from my vantage point next to the driver's mirror, it's quite noticeable.

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[DaveN]

I get the whooosh right between the middle 2 cylinders under the intake manifold. I was starting to wonder if that thermal gasket had melted on track day and now the built up pressure is forced out a gap in the seal when the engine is turned off. In the picture you can see how much gasket is now visible, I doubt there is very much at the mating surfaces. <img src="/forum/images/smilies/968/sad.png" class="smilie" alt="" /> That would explain my high idle as there is a small leak in the malformed gasket. My high idle is only after the car warms up as well further pointing to that gasket as it shrinks when cold (sealing) and expands when hot allowing the leak.

Eric - the thermal gasket, according to Flash and Pete, is supposed to reduce intake manifold temps a bit so better zoomzoom with the SC.

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[flash]

that's what everybody says. for the cost, i figured "what the heck?" i haven't had a leak problem though.



did you over-torque that gasket? did you fail to use the copper spray on it?

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[DaveN]

Gasket was tightened to P-spec. Pete or others never mentioned any copper spray before installing - Ack! I did put a light coating of copper high temp RTV on it before I torqued it down but that should have only helped.

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[flash]

actually, rtv could create a leak. it doesn't stick to the plastic.



there is a copper spray gasket that he told me to use, and what i have generally used on all intake gaskets for a very long time now.

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[DaveN]

Now that the old girl is getting a going over (see new post) I will replace that gasket. I had put a little RTV there because when I removed the old gasket this winter I noticed oil discolouration/staining on the teflon and what appeared to be gasses pushing past the seal.

I will look for this spray and use it on the new gasket. You indicate it's general use on any type of intake gasket material?

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[flash]

i used it on any intake OTHER than the perforated metal type, which is designed to compress and seal.

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