HOZZMANRX7

iTrader: (43)

Correct me if I'm wrong, but the Water Temp Switch is mounted onto the radiator and connects to the harness via two male bullet connectors. The Water Thermo Sensor mounts to the back of the housing that holds the thermostat.

Where I'm going is my recently completed Turbo Vert will NOT hold an idle when cold, but has a nice strong idle once it warms up. In a separate thread regarding testing the Thermo Sensor (found using the search function ), it suggests a faulty Thermo Sensor is the cause of this symptom.

However, I installed a S5 style Koyo radiator into my S4 Turbo Vert. The Koyo didn't provide for mounting the Water Temp Switch. So, on advice from this board, the two bullet connectors from the harness were mated together since the Water Temp Switch had to be eliminated. Suggested there should be no problem in doing this unless I'm starting the car in a Winter/Cold Climate situation. However, it's been 103 degrees HOT lately, so that certainly isn't the issue here.

My suspicion is that the absence of the Water Temp Switch is the cause of my cold idle problems.

Opinions? Suggestions? Solutions?

jd to rescue

iTrader: (3)

You are correct as to which is which. I suspect it is the problem, but a simple test could be done to resolve any doubts. Simply hook the wires to the bare thermal switch and see if it cures your cold idle problem. It would not need to be in the radiator for a short operation of the engine to see if it corrects the idle. The switch simply communicates to the ECU when the coolant has warmed sufficiently to return to a normal hot idle speed. The test connection would not do that ultimately as it isn't reading the change in the coolant temperature. If it fixes the cold idle, however, you then know that you need to tap the radiator to install the thermal switch. There may also be a resistor set up someone has devised on here to off set this. Or, simply put up with a poor quality idle while the engine is cold.

HAILERS

The water temp switch either *makes* or *Breaks*. When the water is over/under 65 degrees or so, the contacts *make* and put a ground on an ECU pin telling the ECU that the water is now over 65 degrees.

So since you have no switch in the bottom of the radiator, just couple the two wires together. Like I said, one wire goes straight to ground. When the switch *makes* the ground is put on a pin on the ECU. Ninty percent of the time the switch is *made* on a normal car.

That *ground* mostly effects the Relief solenoid and the ACV. I think it has little if any effect on fuel delivery.

Fuel delivery seems to me, to be effected by the water THERMO switch seeing 120 plus degrees , whereupon it then leans the idle mixture out. As seen on a wideband and a RTEK2.0

HOZZMANRX7

iTrader: (43)

Hailers (or other with technical insight)

I get what your saying. This means that unless the car has been sitting an extended period of time in under 65 degree temperature, then the water temp switch has no influence on things. And, as I mentioned, I had already joined those two connectors grounding the circuit as you described.

My problem is even after my car has been sitting in 100 degree temperature prior to starting, it still won't hold an idle until the engine approaches normal operating temperature.

Do I have a bad Water Thermo Sensor, bad wax pellet on my throttle body, or what else might be the cause?

RotaryEvolution

iTrader: (30)

your thermowax is not working or was removed previously.

HOZZMANRX7

iTrader: (43)

That was Roberts first suggestion. So, grabbed one off a parts car to swap out. Will report results.

So, you don't think the Water Thermo Sensor is a possibility?

HOZZMANRX7

iTrader: (43)

Not only with my Turbo Vert not hold a cold idle, but there is no 1200-3000 start up fast idle.

Still the ThermoWax?

Fero313

iTrader: (1)

Sorry for bringing this thread back, but it has information and symptoms relevant to my problem and doesn't seem to be solved yet.

I just recently installed a rebuilt motor (4-5k) that runs fine except for it will not hold an idle when cold. around <70 degrees. If I press the gas during this time it dies. I know the thermowax is a little fubar, but once it stays running it rises to a little over 2k or so. I will have to let the car war up before being able to put the engine under any load or it dies. After about 1 min or so it will be drivable and within 3 minutes it will be perfectly fine and startup all day long with no problems. The car has no hot start problems and has good compression. It seems to be temperature related and in my opinion i don't see how it could be the thermowax because that is really the same thing as giving it gas with your foot. I was thinking one of the thermoswitches but from searching most threads are about how start not cold start. What are my possible sensor problems?

Fero313

iTrader: (1)

bump... when I get a chance I will test the sensor on the back of the water pump and the sensor at the bottom of the radiator to see if they are within spec... Can anyone tell me what the plug on the harness should read if I probed the connector for the sensor on the waterpump? I'm just looking to tell if there is a break or a reason why it night not be getting through to the ecu.

HAILERS

What year car do you have. It's confusing. The series five don't have a water temp switch on the bottom of the radiator and your profile says you have a series five. Confusing and can't give an answer because of that.

On a series four car, I'd say just go to your ECU and the green/white wire in the middle plug. Pin 2I and backprobe it with the meter on dcvolts. When cold the thing will read as high as 2-3 vdc but as the engine warms up the thing drops down to 0.4 to 0.5 when fully warm. If you start out cold and see the voltage droping at a steady rate and down to those figures then I call it good.

The wire on a series five???/ Got me. Also you could remove the thing from the housing and test per the FSM but I consider this a waste of my time. Not required.

Or if you have a RTEK2.0 just watch the water temp on the screen rise and if it looks normal it's good to go so to speak.

Fero313

iTrader: (1)

i do have a s5, but this is for a 87 n/a... thanks i'll give it a try. I don't know if there has been much experience with this, but is that switch the probable cause of the cold start problem. When it dies it just dies, like letting the clutch out with the brakes on, so i'm assuming its going too lean at idle... (maybe the ecu not richening up enough when cold?)

Fero313

iTrader: (1)

Ok,

Voltage at 2I: 4.95VDC (voltage is the same at all times when IGN is on)
Continuity between G/W wire at ecu and at thermo sensor connector: yes
Continuity between Br/B wire at ecu(ground) and at T.S. connector: yes
Continuity between G/W and ground: NO

It seems that the connector is broken. I can probe it, but the wires are damn near pulled out of the back and falls off the sensor easily except for when I use the metal clip(its an injector style clip). I am going to get another connector and try that.

2 things:

is the 4.95VDC because of the no continuity with the sensor?
could this be a reason for my cold start problem?

HAILERS

It probably is your problem. I've looked at that pin 2I with everything connected up and I've never seen more than about three something volts (memory). The voltage your seeing means to me the sensor is *open* somewhere. I assume you had the sensor connected when you backprobed the pin 2I and the plug was on the ECU when you did that.

If the ECU sees a open circuit, then the ECU defaults to 176 degrees. Makes for a difficult start if the outside air temp is cold and therefore made the engine coolant temp cold overnight.

The ECU will run the engine rich and when the water temp is around 120 degrees the mixture will go leaner. I've seen that with a wideband and watching the water temp time and time again.

Yeah, you were probably right and it was the water thermo sensor causing the problem. Personally I've never seen a bad water thermo sensor ITSELF.

RotaryEvolution

iTrader: (30)

i have seen on a number of occasions the water thermosensor and fuel injector connectors in the clip the pins get pushed back in the plastic housing, i just dealt with a thermosensor connector that had a pushed in pin on friday.

this will set a code though, i am finding many people are simply not doing the simple procedure of pulling codes though, it rules out MANY possibilities and makes our lives helping out here much easier..

Fero313

iTrader: (1)

i didn't think there would be codes without a engine light, or at least not stored ones... i'll try it tomorrow and see if anything shows up...

Karack,
it seems that the pin deal is what is happening. was the car having the same symptoms as mine? did you just replace the whole connector or did you fix it?

RotaryEvolution

iTrader: (30)

sounds similar in symptoms to a faulty thermosensor signal. i popped the boot off the connector and jammed the pin back into it and connected the clip to the sensor while holding the wires in place then i put some liquid tape(you can get it at kragens, orchard supply or most any hardware or automotive store) over the back of the connector, slid the boot back into place and slapped some more on it as well and put the alternator back into place and all was good.

82BUCKET

iTrader: (4)

Just found this thread and wanted to add my scenerio to it and see if someone might be able to confirm the problem. Ran into a heating problem with car after alt. belt tore and ripped upper hose.....yup..sucked. After replacing or cleaning all components...issue remains. I started with replacing hose of course, replaced thermostat with OEM-Mazda one, coolant...drove it for two days...no issues....but a little higher temps. than normal for my car, no biggie....then on a short drive...not hard...there goes temp....good pace to H....after replacing pump....only cuz I never had....same symptoms....at random times....temp. goes up...idle rough...starts....rough....but does start....took radiator out and took to get cleaned, pressure tested, installed, same scenerio.....Fan clutch seems to operate correctly....could this be the Temp. Switch? Car is 87, S4, 13B N/A, 5 speed. When warm after rough idle, car runs like a top!...normal...haven't done compression test....didn't feel I needed to be concerned with that yet. Thank you in advance for any help.