Throttle Body and IAC (ISCV) Cleaning

Yes, that really is my car with the throttle body out and lying on the ground. I have no idea why there's a pile of rusting bike parts littering my work area, I need to clean up. Box that shit up. Yeah.

For the record, although you do see the Haynes manual pictured, it was pretty useless. This article is vastly more useful. Remember, of course, this is for the 1.6 - I don't know if the 1.8 is different.

I attempted a non-invasive cleaning with no real results. Apparently, so had the previous owner, as the main mounting screw for the plastic air intake had been removed. Permanently. So I need another one. However, spraying the face of the throttle restrictor plate is not going to fix idle problems.

When cold, my ISCV (idle speed control valve) worked perfectly, compensating for extra load (like A/C) exactly as it should. Idle was right around 900 with the idle control screw pegged shut. As the engine warmed, the idle would rise to about 1200-1300 and the ISCV would stop working completely. Turning on the A/C would almost stall the car at idle.

This made me think I had a very dirty ISCV. I mean, had it even been cleaned in the 102k miles the car had been driven? I have absolutely no records for this car.

Well, how does it look to you? I think it looks pretty filthy. That's the back of the throttle, by the way, with ISCV still attached.

The Haynes manual refers to the ISCV as the IAV (Idle Air Valve). I think that ISCV makes more sense, as there is another valve that's also an 'air valve' but responds to coolant temperature, not the ECU. I haven't been able to find that valve referenced in my Haynes manual.

ISCV removed. I think the hardest part of all this was putting that stupid gasket back in. It was way distorted, probably from heat, and much too big. Ended up using a simple, latex based adhesive on the back side of the gasket, applying pressure, and praying. I'm pretty sure it got back in it's groove, finally, as it's a very thick gasket and the ISCV seated without a gap of any kind and not a great deal of effort. But that was awful, and if you can find a new gasket for this, do so and save yourself some serious frustration. Or share with me your secret for getting a swollen gasket to stay in place.

Look any better? That's about halfway through cleaning it... I eventually pulled the gasket from the groove which proved to be a silly thing to do. Silly me.

Oh yeah, and that's the inside of my intake manifold looked before cleaning. Nice.

That's about all there is to it, really. I'm happy it all went back together, the ECU isn't throwing open ISCV solenoid codes like it used to sometimes, and so far it seems the idle problems are cured. At least, the ISCV problems. I now get a nice steady idle at all engine temperatures and the ISCV works whenever I test it. Of course, it's not over - I am suspicious of the other air valve. But that one's a lot easier to get to.

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