Ecu Temp Sensor

[mikej]

2001 MK2 2.3 , Hi all i am looking to replace the ecu cold start temp sensor with a resister for testing purposes i am still experiencing issues with rough running from cold for approx a minute or so and would like to try it with a resister first, would anyone know what resistance this sensor is when engine cold so i can purchase one or even offer an alternative method apart from the buy a new one method ?

thanks.

[Mirez]

2001 MK2 2.3 , Hi all i am looking to replace the ecu cold start temp sensor with a resister for testing purposes i am still experiencing issues with rough running from cold for approx a minute or so and would like to try it with a resister first, would anyone know what resistance this sensor is when engine cold so i can purchase one or even offer an alternative method apart from the buy a new one method ?

thanks.

 

Is this an air sensor? If so then an easier way would be to take it off the car and measure the resistance with a multimeter - you can then use a hairdryer to simulate warmer air passing over it and measure the resistance again. I wouldn't be suprised if the resistance drops with temperature so you would need a high value resistor for your bridge but if you measure a destinct change in values then its unlikely to be at fault.

[mikej]

Hi Mirez i have actually been thinking if this sensor does come into play on startup ? however the one i am refering to isn't this. I think there are two temp sensors for the engine, 1 for the actual temp gauge display and another used by the ECU on startup to determine the amount of fuel to supply the problem i am experiencing is so bloody random i cannot pin point it, one morning it's fine then the other its as rough as a dog even though the outside temp is roughly the same and my revs although constantly rock steady are not the same on choke give or take a few hundred. I am proberly barking up the wrong tree here and did think vaccum leak but the fact i can't find one and its there one day and gone the next makes me believe it's poss electrical ? :lol:

[Mirez]

Sounds electrical indeed, I would be suprised if the intake sensor would cause that much trouble though, the adjustment levels the ECU can make arn't really that great and I *think* it cross references this signal with that from the MAF. Have you tried disconecting both the IAT and MAF sensors in turn when its doing it? The ECU should use a "fixed reference value" as soon as it sees the signal isn't present so you should be able to rule both sensors out reasonably easy.

 

I would be looking at the coil packs myself - I have had them before where they begin to fail internally which seems to show up more when cold. Does it feel like its missing?

[Scorpiorefugee]

Is this an air sensor? If so then an easier way would be to take it off the car and measure the resistance with a multimeter -

 

Sadly, if it is faulty, measuring it will not help much unless you already know what it should be.

Unplugging it may indate something or try shorting it out as an alternative. The ECU should cope with either case if it was designed by anyone with a sense of responsibility.

[Mirez]

Not quite :lol: Since everything works ok when warm then measuring the resistance value of the sensor across the range would be usefull in finding a suitable value resistor in which to bypass the sensor with as per the original request.

 

I would strongly recommend against directly shorting any sensor! Whilst you are right that a well designed ECU will cope, we dont know how well designd this one is! You are also making the assumption that its "just" a simple analogue sensor and that there isn't more to it! :16:

[mikej]

Hi again, the sensor i have been looking at is situated next to the actual temp gauge sender in the coolant system as i thought this was the one the ECU looked at ?, i have disconnected the maf and the car runs like a bag of nails, only one coil on mine it's the later 16v engine and this has been changed for a known good one. The issue i have occurs only on cold start and lasts for approx 1 minute or so after which the car runs like a dream however some mornings it's fine and others it's a bloody pain, feels like i filled it with kangaroo juice. What i have noticed like already mentioned is the RPM on choke, it is working but sometimes it's a steady 1250 and other times it's around 1100 and steady. Once off choke it idles spot on @ 750. It's driving me nuts to be honest and i am looking into purchasing an OBD2 interface to use with some scantool software in the hope it may shed some light on it but thought i may try and simulate the sensors first, where is the intake sensor then?