IAT Sensor

[Mr T]

Hi guys, I've just noticed the intercooler fan on my Mk5 never runs?
I'm sure it used to & in this weather I'd have thought it would of run after shutting the engine down, due to heat soak.
Also there is a noticeable smell of petrol, as if the engine is running rich all the time.
I've had a look on Evilution.co.uk & Kane suggests the IAT sensor could be at fault.
Well I've taken the sensor out & given it a clean. I also put a meter across it & got a reading of 3.8KΩ, is this correct? Not sure what type of sensor it is, so not sure of it's o/p.

Thanks
Martin.

[tolsen]

Re: IAT Sensor

Smart 450 IAT sensor P/N 000542 2818 resistance versus temperature:
-1C ~ 16.6 kOhm
+5C ~ 12.9 kOhm
+17C ~ 8.7 kOhm
+30C ~ 4.0 kOhm

[Mr T]

Re: IAT Sensor

Thanks tolsen for those figures.
So 3.8KΩ would of been about right as it was about 27˚C at the time.
Do you know if the IAT operates the choke/fast running at start-up? As my car didn't come off choke for a couple of mins this morning, even though it was 16˚C at the time.

[Kapt. Q]

Re: IAT Sensor

I would guess that fast idle is triggered by coolant temp not IAT. A heatsoaked intercooler should make the car run leaner, not richer.

Cheers!

[Thrumbleux]

Re: IAT Sensor

Do you know if the IAT operates the choke/fast running at start-up? As my car didn't come off choke for a couple of mins this morning, even though it was 16˚C at the time.

My car currently has an intermittent problem where boost isn't always available from cold start-up. I've been advised that turboed motors are set up to prevent boost during initial warm up and read from the IAT sensor to do this.
Noticeably, a fortwo in the fast idle phase following cold start holds the turbo wastegate open and closes it when the revs drop. Listen closely and you can hear the turbo start to spin up when this occurs - on a properly working car that is.

Taking a couple of minutes to settle to a normal idle in these temps should not be happening.

[Thrumbleux]

Re: IAT Sensor

Cleaned my IAT sensor yesterday (and replaced another part as well so not entirely conclusive) and it's running a whole lot better today.

Easy job - 5 minutes and some brake cleaner, cotton bud if you're fussy. Worth doing I reckon. Add it your service schedule.

[Mr T]

Re: IAT Sensor

I managed to break one of the retaining clips on the IAT sensor... & the other clip is just about to go. So I've had to order a new one.

[tolsen]

Re: IAT Sensor

Remove plug from sensor first, then unclip sensor. Sensor cannot be unclipped when plug is attached unless you break one of the two catches.

[Mr T]

Re: IAT Sensor

I found that out the hard way!...Doh.

[Mr T]

Re: IAT Sensor

Fitted the new IAT sensor today. The smell of petrol has gone away & the intercooler fan is now working again.
Might also get better MPG as motor not running rich now.

[Thrumbleux]

Re: IAT Sensor

Mr T: If this has been going on for some time - consider changing the engine oil - or at the very least give it a good long (gentle) run. The oil may well be fuel diluted. Have a sniff under the oil filler cap for petrol smell.

[Mr T]

Re: IAT Sensor

It burns a fair bit of oil, needs a rebuild really, but I'll have a sniff of the oil & it's due a service, so oil will be changed then. Thanks for the heads-up.