IAT Sensor, Wire broken

[JonathanC250]

Hi all,

Further to my other post, I have found out what the sensor with the broken wire is, Its the Intake Air Temprature sensor.

What does this do, and will driving the car untill the weekend when I can fix it cause any problems?

I'm hoping to be able to open the plug up and put some new wire in and join it up further up the cable, so its not as tight.

Thanks

Jon

 

[JonathanC250]

It seems that driving with the IAT Sensor wire snapped, has affected the way the car drives.

When pulling away or driving the car with low revs ( Turbo not boosting) it feels a little slower or a bit more laggy.

But when the turbo kicks in, it feels like its boosting harder and the car feels quicker!

What does this sensor control? Amount of fuel or how much the turbo kicks in or something else?

Any help would be appreciated

Thanks

 

[Tinkerer]

Without going into too much detail, the mass of air is affected by it's temperature and therefore this is needed, as you suspect, to calculate the amount of fuel that will be required to go with it. When the turbo kicks in things can get a little bit more complicated as compressed air gets warm and expands which may negate the effect of the turbo, hence the reason for an 'intercooler' which is fitted to a lot of turbo diesels. Not too sure how this applies to a Merc.

 

[JonathanC250]

I had a look at this over the weekend, unfortunately it would appear that I can't open up the plug to put new wire in!

Does anyone know if the cable that attaches to the IAT sensor has a plug at the other end of it somehwere, so that I can order that cable, or is it part of the engine loom?

I really want to get this sorted out, I dont like driving my car with faults!!

Thanks

Jon

 

[alan350CDI]

If it has snapped off at the plug you can either add new terminals, (for which you will need a ratchet crimp tool) and add a new plug housing. There are quite a few places that sell housings and terminals: M-cal is just one.

Either that or you could cut your loom back and solder in a connector with attached wiring pigtail which you could get from any scrap car with the same temperature sensor plug.

I believe that usually when your ECU sees no IAT value it will default to 20degC. This would account for why your car feels quicker on boost and slower off. Right now it is colder than 20 degrees outside, so your car will be running a touch lean, therefore injecting not quite enough fuel off boost. Your car is most likely mapped as standard to be a little bit rich on boost (this is quite common) so leaning it off a touch actually improves power most likely.

 

[IanPS]

I had the same problem with my 220 cdi.
With great care, I succeeded in taking the plug apart and soldering in new wires which I then soldered to the broken off wires. The original wires were rather short and quite brittle so I've added length and flexibility. You will need a fine soldering iron and a steady hand or three.

 

[JonathanC250]

I've got a 1mm soldering iron, would that be fine enough?

How did you manage to get the plug apart, thats the part i'm having the trouble with!

Thanks

Jon

 

[Dieselman]

If you can't part the plug heat the metal contact up from the back of the plug then shove in the tinned wire and add a bit more solder.

 

[IanPS]

Sorry for not replying earlier, been away.
On mine I unclipped the plug from the sensor and then gently pushed the innards out the way the wires went in. I.e. push from the sensor side. Once the insides came out they fell apart and I spent the next 10 minutes trying to find the bits, so make sure you're working over a suitable surface. A 1mm soldering iron should be fine.
Not sure about heating up the back of the plug. There's a lot of rubber in there.
Good luck.