on my '87 n/a fc3s I noticed a sensor with 2 individual leads mounted on the bottom of the radiator, drivers side. what is it and what does it do? I searched the forums and checked the wiring diagram but am at a loss. the car seems to run slightly COOLER and smoother since I connected it. (could be coincidence) thanx ~rich

btw, my engine is a street-port rebuild and doesn't have a sensor on the coolant filler neck - is that a bad thing that sensor is missing? the car the motor came out of had a drastically modified wiring harness done by pros but was too brittle from heat to be used in my transplant car. mebbe the modified harness had this bypassed?

I always assumed everything was working properly but now I'm wondering if my ecu is defaulting to a fuel rich default mode cause it's missing the temp sensor... (gas mileage could be better I feel)

 

It is a coolant tempature sensor for the AWS system.

Some cars had this, some did not.

The only rich mode I am aware of on a S4 is if the water thermo sensor was bad. The ECU will try and richen up the car thinking its cold for emissions reasons.

 

Iceblue..thanks on that reply.. I too was wondering what that sensor was for..just replaced my rad and broke the connectors on the wires..got some connectors back on though..connectors are called FEMALE BULLET CONNECTORS..22-18 awg..they fit perfect on the sensor pins..for anyone that needs to get them..

 

thanx 2 iceblue - you da man. ~rich

 

It's a temp switch (not sensor) that is used by the emission control system. It's not just for the AWS.

It will not have any effect on engine temp, or any other noticable effect on engine performance.

That's another temp switch, this time for the axiliary electric fan fitted to some models. If your car doesn't have this fan, it won't have the switch either (even though the wire is there).

It's not connected to the ECU in any way, so no.

Nope. If the ECU's thermosensor is bad the ECU will default to a coolant temp of 80degC/176degF, which is only a few degrees below normal operating temp.The engine will run poorly when cold because the ECU would normally be adding more fuel to compenste for the cold engine. Once it's warm it will run normally, perhaps slightly on the rich side because of the temp difference. None of this has anything to do with "emissions reasons".

 

According to GM the purpose of AWS systems was to improve emissions to heat the cars up quicker so that emissions systems are working properly and polluting less. This is the reason they dump more fuel into them and rev them higher on start up.

 

thanx NZConvertible and iceblue.

 

I've a suggestion. Re-read what the NZ wrote. I've no clue why you copied his words then wrote what you just wrote. The NZ is talking about the water thermo sensor and your replying about the AWS and seemingly about the water temperature switch.

If you leave the connectors off the water temp switch, you'll find that your acv will be dumping air into the silencer in the right front fender instead of the exaust ports. Acutally I can see how this would effect your idle if you had a leaking anti-afterburn valve in the acv (leaking unauthorized air into the intake manifold corrupting the idle). EDIT: On second thought, you probably don't have the airpump or acv connected up so that won't apply to you.

Hmmmmm, so Mazda is a subdivision of GM???? humor

 

Maybe I am just being confusing. The subject was not directly about the water thermo sensor or switch. It was implying why the ECU reads them and one of the reasons there is an AWS system, and why the ECU dumps more fuel when it thinks the car is cold.

NZ said it had nothing to do with emissions. So I stated the GM has made efforts in their schools to state that when the car reads cold id dumps fuel in to heat it up and burn off emissions bettor. One of the ways it does this is from the Water thermo sensor. A great example of this is the oil thermal pallet in the front eccentric shaft. The only purpose of this is to heat the oil up quick to reduce emissions.

I dunno maybe I am just veering off the subject and off a cliff. Anyways gave it an effort.

 

jesus, who cares.... the questions were answered for the poster already.

 

Firstly, yes you are confused because this is not what I was referring to. As Hailers said I was talking about the thermosensor, which has nothing to do with emissions. Go read the post again, I quoted what you said. Secondly, the AWS is there to heat up the pre-cat quicker, but they do not "dump more fuel into them" for emissions purposes. That's completely false. All engines need extra fuel when they're cold because a lot of the fuel condenses on the cold engine surfaces instead of staying in a vapour, and this obviously results in poor combustion efficiency and poor engine performance. This is why carbs have chokes and EFI systems have coolant temp compensation fuel maps. It has nothing to to do with emissions, if anything it makes it worse.

You need to think about that statement a little harder. "Emissions" is the result of poorly or partly combusted fuel. Adding more fuel is not going to burn that off, it's going to create more emissions. I think you've just misinterpreted whatever it was that GM said.

Um, sort of but still wrong. The e-shaft thermal pellet doesn't heat the oil up faster, it disables the rotor cooling jets, so that the engine's internals heat up faster. There is also a thermal pellet in the oil cooler, which disables it until the oil heats up. That's probably what you were thinking of.

 

Agreed.
Addressed in next paragraph.

Hehe I knew this was going to come up. I avoided it b/c of the complexity of it. I see what your saying maybe I misinterpret what they are saying. How I see what they are saying is. Your point of heating up the precat is dead on you known this and this reduces emissions. Yes the cold motor needs more fuel to run. But by accelling the motor and adding more fuel it will heat up quicker and get to fully functional emissions sooner even though the early parts are worse. This may just be a contradiction or how they planed it; I don’t know, im not the engineer. But that is how I gathered that words.

Oh you got me there. Agreed, pore communication. It stops the oil flowing to heat the internals up to operating temps for emissions reasons. B/c warmer engines produce bettor emissions.

The thermostat pellet in the oil cooler is to sustain a proper oil temp in the motor but nothing to do with emissions.

“I know I am preaching to the wind to you nothing new, just crossing views to come to a best conclusion possible”

 

You're totally misunderstanding this. Revving the engine higher and adding more fuel are two totally seperate functions for two totally sperate purposes. Adding more fuel it will not heat the engine up quicker! Fuel does not magically burn on it's own, it has to be in the presence of oxygen from air. If you dump in excess fuel it will go straight out the tailpipe. In this case it's added to compensate for condensed fuel that doesn't burn like I said.

 

Ok
Yes basic physics here.
Ok cool.