fonetico

My local Toyota dealer serviced my wife's Yaris last week and agreed to include an oil change for my S4 for a very reasonable price.

When I collected the car, he suggested my idle speed of 950 rpm was excessively high and could be caused by a hole in the oil breather tube.

I've always assumed the high idle was normal.

What's the normal idle and what's the oil breather tube? Would it be a simple operation for me to replace it and what's the part number?

I've consulted the WSM and the Katalog but they only seem to refer to parts generically.

MainePorsche

Hose 53 goes from the base of the oil filler neck and exits from under the intake to attach to the valve cover. It takes aerosolized oil vapor from the crankcase and recirculates it back in the system. On the engine pic it is the black hose just aft to the crossbar on the side opposite the throttle cable quadrant (left side when looking at the pic). I've never heard of this being involved with idle issues.

fonetico

Ah!!! Thanks for that.

Within the last 3 years I've replaced the ISV? and the throttle switch on the quadrant.

2 months ago upgraded ECU.

Should I now be looking at vacuum lines?

MainePorsche

Yes.
Always look to your vac lines. They are relatively easy to deal with, and will keep a number of systems working normally. That crankcase breather hose is not really a vacuum line. Unfortunately if it is violated, the intake has to come off to replace this simple hose.

fonetico

Oh no!!!!

Why is nothing simple with this damned car?

Thanks anyway.

MainePorsche

Check the hose with a small light and even a telescopic mirror. It may not have an issue.

fonetico

Unfortunately it's 8.30pm here in London so I'll check it out in the morning.

Is the hose accessible enough that I could repair it with gaffer (duct) tape?

MainePorsche

If the rent in the hose is up top-yes. If the rent is down under the intake-no.

fonetico

Thanks. Your help much appreciated.

MainePorsche

Sure.
Perhaps an engine control expert can speak to your high idle.
I'm not completely there yet.

FredR

To create a fast idle the system has to leak unmetered air through aged rubber that may be cracked or even split. The more obvious candidates on these motors are the inlet and outlet hoses to the ISV. There is also the small hose from the side of the filler neck that combines with the tank vent system and goes to the nozzle on the inlet manifold. Unfortunately all these items need to inlet manifold off to get and inspect.

An idle speed of 950 rpm is wrong- it should be 675 rpm. Assuming you have an automatic model the motor is likely starting to drag at that speed and that is not helpful.