[urq] Re: Intake temperature sensor

[Buchholz, Steven]

... here is info transcribed from the IST docs ...

**********
Intake Air Temp Sensor

The electrical signal from the intake air temperature sensor changes as
the air temperature varies.  This signal is processed in the timing
control unit whenever boost pressure is above 1.1 bar.

In general, the intake air temperature sensor will cause ignition timing
to retard as air temperature increases.  This helps to prevent engine
"knock" or "pinging".  Location: front of intake manifold
**********

Based on this, I wonder if an IAT sensor could have any bearing on a
cold starting/warmup problem ... and if you're seeing issues any time
the boost is below 1.1 bar then that would contraindicate the IAT as
well.  The IST docs indicate that an open circuit on the IAT will force
a 4K RPM cut out ... do you ever see this?

I'd recommend that you run your issue through the troubleshooting guide
in the maintenance and adjustments doc ... I also find it valuable to
read through the description of the various sensors and what they are
used for ... 

Steve B
San Jose, CA (USA)
> 
> So what is this component - some type of NTC resistor? Is it 
> a commonly available part that can be spliec/resoldered in? Source?
> 
> Ben
>   ----- Original Message ----- 
>   Sent: Thursday, March 03, 2005 1:30 PM
>   Subject: Intake temperature sensor
> 
> 
>          Absolutely not Ben! The 5000 has a much higher 
> resistance of 400 ohms rather than the 20 ohms used by the 
> MAC02. You can easily check with an ohmeter AFTER 
> disconnecting from the ECU. You could also check by measuring 
> the voltage across the terminals with the ignition switched 
> on. I do not have the expected value here but can e-mail it 
> to you from home late tonight. I have a spare that you could 
> borrow temporarily if necessary.
>          Martin Dapot
>          83 UrQ
> 
>          UrQ sensor part number       035-905-379B          20 ohms
>          5000T sensor part number    034-905-379B          400 ohms