[urq] Engine Warmup Operation

[Buchholz, Steven]

... I don't think I'd try to put too much value to WX idle speed vs. engine temperature.  As long as the RPMs are high enough to be above the ECU's idle regulation mode the only things controlling the idle speed are the aux air regulator a heated bi-metallic bypass device) and the idle speed adjustment screw on the TB.  Remember that these cars predate ISVs ...

If the behavior of a particular car changes it would be a clue that perhaps there's an air leak or impending component failure ... but comparing the behaviors of two different cars is as likely to send someone on a snipe hunt as down the path to a real problem ... 

Steve B
San José, CA (USA)
> 
> >    I take it that the idle speed should be constant during warmup, say
> > somewhere between 850 & 1000 RPM?
> 
> On my stock WX, that is correct. Exterior temperature can be as low as -15C
> or as high as +30C, startup idle speed is always the same.
> 
> It doesn't ramp up to ~1500 for a short
> > period like most EFI systems and then drop back to 850?
> 
> No. However, I found that the idle speed is not perfectly stable. If the
> engine is very hot, idle speed will go up a bit for a few minutes. It seems
> to be temperature related (underhood temperature, that is).