coolant temp issue ??

Afternoon gents,
I have had a quick retest on the rangey and it isnt good news I am afraid.Emissions not quite right after replacing a few components. I am kinda thinking the coolant sensor has gone up the swanny inducing a cold start mixture. The multiplug is a round 4 wire type on top of the engine. I do not do electrics, but can somebody tell me a method to bypass the switch and create a hot start situation which will reduce the co.

You need to tell us what rangey you have. P38, classic or L322?

I doubt its a temp sensor fault, does the temp gauge work? On later models there's 1 temp sensor and the ECU tells the instrument pack where to put the gauge. does it run rough? does it missfire?

If the temp sensor fails the the ECU will default to to around 60 degrees, this is neither cold or warm but enough to give resonable hot and cold starting/running (kind of a limp home mode).

If you have to bypass it then you need to know the resistance of the sender when at operating temp, then fit a resistor of that value to the connector, you'll get poor/no cold starting though.

Check for things like air leaks on the intake system, this will give low co but the hc's will go through the roof

Many thanks for your reply. The Rangey is a 4.0 ltr T plate and I believe the coolant sensor on top the engine as with other cars can cause all sorts of issues if faulty.
The lambda result was .940 and needs to be above .950, co is currently 2.0% I agree on the resistance values mentioned, my logic was to switch the two related wires to enable a better hot start.
I am taking it to a lad next week to put it on his T4 and see what the live data is doing and check/erase any stored fault codes. Thanks again.

you could have an oxygen sensor fault, when you check live data, make sure both oxy sensors are switching rapidly between 0 and 1 volt, if one or both are not switching at all or not covering the full range then replace it, small exhaust blows will cause the lambda readings to be out as well as faulty oxy sensors

Parts replaced were the MAF sensor , both Oxy sensors and cats. It failed on the above readings for the second time which is when I posted the start of this thread.
The customer took it away as he needed it and he took it elsewhere to see if it would pass and it did I have yet to see the emission print out but he is pleased it has gone though on all counts co/lambda etc....

Cant quite see it meself but I am glad its off my case.

I have had this type problem on a 1.8 freelander once before, replaced the cat and oxy sensor (both were well shot) but it still failed on emissions, it eventually passed after giving the car a good thrash up the road to get the cat up to temp and working properly, seemed the cat was not operating properly and not getting hot enough.

It makes sense to me, rag it up the road and then do a test on it.
I appreciate your time to post up your replies.Many thanks.