Top tip for curing Smelly exhaust fumes on EFi engine

[Mike E (uk)]

I have had a smelly exhaust on the 16V BX for a few years, where it has been running a bit rich but still passes the MOT.

Fitted a new engine temp sensor,for £5,and the problem has gone away.
I measured the old one ages ago, but it had not failed completely, so I thaught it was OK.

Big thanks to Kitch for suggesting this to me after he changed the same part on his car.

Mike

[Kitch]

I gained 2bhp with it too!

In seriousness, if the AFR isn't right, there are only a handful of things that can affect it. CTS is one of them - if the ECU is being told the coolant is colder than it really is, it'll needlessly be richening the mixture.

[Philip Chidlow]

This could be something for Mark Smith to consider as the 16v was a bit fumey in France?

[Kitch]

All 16v's are fumey to be fair - never had one that isn't. Mine was pretty excessive though!

[Vanny]

now thats interesting, never thought the water temp sensor would make much difference, but i know mine is out (comparing resistance to actual temp), might have to give it a go!

[Jaba]

I checked mine on my 8v a couple of years ago and the resistance was spot on at both ends of the scale. So they don't all become inaccurate with age. Another critical one I suppose is the air inlet temperature sensor.

[Vanny]

where did you get the sensor mike? i can only find them for £10 on the evil bay.

[Mike E (uk)]

Seller: platinumcarparts ( 9934 )
Seller information: VauxWorld Ltd
Vaux World Ltd
Unit 6 C - Dingle Farm
Church Lane
Newton, Lancashire PR4 3RX UK

Item title Price P&P price Quantity Item total

Peugeot 106 205 306 309 405 505 EXPERT WATER TEMPERATURE SENSOR - NEW ( 270864353671 )

Paid on 24-Sep-12 £5.45 £1.00 1 £5.45

bought though Evil bay, but only £6.45 inc !

Mike

[Defender110]

I checked mine on my 8v a couple of years ago and the resistance was spot on at both ends of the scale. So they don't all become inaccurate with age. Another critical one I suppose is the air inlet temperature sensor.

How do you calculate what the resistance is supposed to be, I would like to test mine on my Land rover TD5?

[Jaba]

I checked mine on my 8v a couple of years ago and the resistance was spot on at both ends of the scale. So they don't all become inaccurate with age. Another critical one I suppose is the air inlet temperature sensor.

How do you calculate what the resistance is supposed to be, I would like to test mine on my Land rover TD5?

First of all you need to find the CTS lookup table in the Bosch (?) diagnostics for your ECU.
Then either measure it on the car using the ambient temperature to start with and then watch the resistance change as the engine warms up making an intelligent estimate to allow for temperature gauge inaccuracies.
Or whip the sensor out and heat it up on your kitchen hob using a thermometer and ohmmeter of some sort.

[mat_fenwick]

Or send it to me - I can check it fairly accurately (0.001°C/0.0001 Ohms) It would be nice if my job was actually useful for something...

[mds141]

Which sensor are we talking about? I presume it's not the one which triggers the cooling fans? I might have a go at swapping mine. Can someone post a pic of the sensor in situ please. Ta.

[Kitch]

Which sensor are we talking about? I presume it's not the one which triggers the cooling fans? I might have a go at swapping mine. Can someone post a pic of the sensor in situ please. Ta.

No, it's the coolant temp sensor. Little blue 2-pin plug underneath the thermostat housing. Sends a signal to the ECU telling it how hot the engine is, so the ECU adjusts fuelling to suit (like an electronic choke).
The sensor works through resistance, so if it goes out of range it starts sending dodgey signals to the ECU tricking it into thinking it needs to richen up more than it needs to.

Best way to tell is to hook the car up to an AFR meter. Mine was wandering around 11.8 - 12.9AFR on wide open throttle on the dyno, and after I changed the sensor it was pretty much 12.6AFR all the way through, which is the ideal mix for power (until they really start increasing the amount of ethanol in petrol, but my fuel pipes will have been eaten long before that!)
Bought me at least 2hp IIRC too

[mds141]

Cheers Kitch. If it was running rich would it be noticeable in terms of fuel consumption. If I don't thrash mine on the m-way it'll do 40ish mpg. I recently put new Beru plugs in and the old ones had a really good colour to them ie not too light or too dark.

[Kitch]

If it's running rich it'll be marginally thirstier (we're not talking huge differences here). 40mpg on the motorway is good for a valver....you want to make sure it's not running lean