cold start sencor switch

[rx loony]

Hi guys do any of you know were the cold start sensor switch is ?

[Brett]

Moving this to the technical section.

[Martiny]

Could you be more specific?  I dont understand the question !

[rx loony]

whats happening is the rex is over feuling realy bad i put it on the co machine and the mechanic told me to quickley get it of his machine cos it was that rich,he told me that it would be the hot cold scensor switch or lambda scensor,do u guys have any clues

[rx loony]

come on lads any takers for this one

[Brett]

What modifications do you have? What year is your car?
Its hard to help you out without any other information about the car!
The Lambada sensor may be at fault, however if it is I\'d imagine the car would not be running correctly either.

[Martiny]

Ok, well, it will probably use the engine temperature, and the air temperature to decide how fuel to put in.

Can you please tell us what car you have. A "Rex"  could be anything from 1967 to present, and could even be a bus !!

[rx loony]

its got 2 k&n induction kit full zigen5 exhaust,full uprated engine rebuild,its suposed to be running 310bhp but cant prove that,its a 1992 kplate ifini type r import,it doesnt idle steady at all i have had all the vacume pipes replaced with silicone ones so its not a leek,but when u put the foot down it pulls like a train i dont understand it,please help i am going insane with the smell of fuel

[Martiny]

Right, so a "switch" is a kind of on/off thing, like a light switch.  There is no such thing as a "Cold start" switch.

There will be a sensor or two that will tell the computer, (The ECU) the exact temperature, (rather than just on/off).The ECU will use this reading to put in more fuel if the air is cold and if the engine is cold.  

Fuel helps Oxgyen to burn. The colder the air, the more air fits into the same space, so when your engine sucks cold air, its sucking more oxygen than when the air is warm. There is another factor about all the parts that the mixture flows through that affect the mixture ( amount of fuel to air), but I forget that theory right now !

Ok, so although your engine and the car are warm, if a sensor is faulty, the computer will think it needs to put in more fuel than it really does.

Hold on a sec, I am looking in the factory wiring diagram. You can download this diagram from the web somewhere, I think on ILuvmyrx7.com.

[Martiny]

All right, I have found 2 things. First, there is a "Water thermo" switch ( and it says (fan) in brackets, so I think this just tellase the ecu to switch the fan/s on.

Next thing is I can see "Fuel Thermosensor", and to be honest, I have never heard of such a thing before !!

I cannot see on the wiring diagram an air temperature sensor, and I pretty sure the ECU would need to know this.

To be more honest, I dont think that hot/cold sensor is necessarily causing your problem.

If your car is 310hp, there is no way you have the standard ECU anyway. This means that whatever you have is programmable, and the mixture can be set ( adjusted, or sometimes called mappped or mapping).

Brett is correct. The Lambda sensor tells the ECU whats coming out the exhaust, and then the ECU will try and adjust the fuel injection amount to acheive a relatively good mixture. ( about 14 parts air to 1 part fuel). The lamda sensor is also sometimes referred to as an Oxygen sensor. ( I think it looks for how much oxygen is left unburnt in the exhaust gasses).

Is there a Rotary specialist near you somewhere? Or how do you fancy a drive down to England ?

[Martiny]

Whats a "fully uprated engine build"? Can you be more specific? Have the ports been modified?  This can affect idling if they have.

If the idle is rough, what you need to do first is go and buy yourself a Boost gauge that also reads vacuum.  ( Phone Rotechniks and they will send you one)

Now, when the engine idles, the vacuum should be pretty constant and round about 17 mm ( of Mercury, I think its measured in).  The vacuum gauge will tell us if there are any leaks in the intake system. This leak might not come from your vacuum pipes, it could be from a gasket in the intake system being faulty.

[rx loony]

not one person up here wants to know about the rx7s they just say they are a pain in the arse

[Brett]

When you say full exhaust, do you mean it has no CATs at all?  If so this will account for your higher CO levels.  What were the hydrcarbons like?

 I would recommend you take it to another MOT station and ask them nicely if they can check your emissions for you, the other guy who checked it sounds like a bit of a **** to me.  Once you have some definate numbers to work with its easier to work out where the problem lies.

[rx loony]

i have an apexi boost guage and the needle is as steady as a rock,but thanks u may have sorted another problem for me my 200sx is idling lumpy and the vacume is at 12 and i have done everything from plugs to new feul pump so cheers for that,but back to the rx the guage is in totaky different reading,and its a cat back exhaust

[Brett]

If its a cat back exhaust then I would look to your air pump.  Is it connected up and running properly? If not it may be that you have roasted your cat...