Saturn 95 sc2, idle dies on me..

When cold or only after its warmed up?

EGR or ECT sensor or Fuel pressure. Diagnosing beats replacing.

When warmed up...

EGR or intake manifold leak would be where I'd start looking. Just my 1/50 of a dollar

-WaV

JaY wrote:

when warmed up, is there anyway to check the egr valve..... i looked up the ect sensor but could not find one. anything else it might be called

when warmed up, is there anyway to check the egr valve..... i looked up the ect sensor but could not find one. anything else it might be called

EGR vavle may not be able to close. Clean out any carbon buildup.

Engine Coolant Temp Sensor. 95 was a change over year, you may have 2.

Should i claen it with carb cleaner?

Blau - I have to disagree with you on this one. The ECT sensor goes out "high" or "open". I dont think they short out. If they did, I'm not thinking it would make the engine die from slow idle. That said - I've never encountered THIS particular problem. Not in a Saturn. Checking all other sensors would be a logical plan for finding the problem.

What you said about 95 being a changeover leaves me scratching my head... The only way to tell the engines in my 94 and 95 apart is the way the air intake routes into the air filter box and the difference in the EGR - in 95 the EGR became directly electronically controled rather than the vacuum diaphram actuator. They both have the same temperature sensors in the same places with the same wiring configuration. Did the

95 begin using two O2 sensors? (I havent been down there long enough under the 95 to notice if there was a downstream post-cat-converter O2 sensor).

Three particular sensors I'm thinking of which may be involved are MAP sensor, Throttle position rheostat, and the air inlet temperature sensor.

Peace - WaV

Bl=E4Bl=E4 wrote:

Not sure if Saturns have this problem, but in many cars the idle control valve adjusts the airflow at idle; however, the control depends on a minimum air flow past the throttle plate. If the throttle plate and bore are gummed up so that too little air passes by in the "closed" position (it's not supposed to be completely closed), then the idle air controller runs out of travel and the engine stalls.

What brings this up is your initial complaint of the engine stalling at idle when stopping, such as at a light. This is a classic symptom of a gummed up throttle plate in many cars. I know I routinely (every 30-50K miles) clean the one in my '94 Saturn SW2 after learning that I needed to clean my Plymouth Voyager throttle at that interval. I can't recall if I have ever experienced the same symptoms in the Saturn that I did in the Voyager, however.

It is simple and free to try cleaning and see if it helps your symptoms. It not, then continue with the suggestions of others. If you do clean it, don't just spray carb cleaner in to the throttle area, because the solvents may be bad for rubber parts farther in. Remove the duct from the air cleaner, and use a solvent moistened cloth to clean both sides of the throttle plate, and the bore where the plate closes. Try not to plug any of the little holes in the bore.

That will be f> Blau - I have to disagree with you on this one. The ECT sensor goes out

High or open??? Wtf are you talking about Wavy? If its 10 degrees out or=20

100 degrees out how does the engine richen the mixture when it's cold?=20 What happens if it thinks its cold and its not? And did I say anything=20 about a shorted sensor? The ECT is like a variable resistor. For a given=20 resistance you get a corresponding temperature.=20 16,180ohms =3D 14deg ???..snip 3,520ohms =3D 68deg ???..snip 177ohms =3D 212deg Where's high or open?

The OEM ECT Sensors used plastic tips. They would crack and deform and=20 start giving faulty readings. They can and should be replaced with BRASS=20 tipped sensors to correct this. Are you with me so far? If the ECM=20 thinks its 10 deg in the middle of summer it will flood the engine with=20 fuel and stall out! =20 Coolant Temperature Gauge Sending Unit (goes to dash for "analog"=20 instrument panels) Coolant Temperature Sensor (goes to ECM)

Prior to, and a little during OBD II switch over I think, Saturn used=20 two ECT sensors. One is for the gage on the dash (if you have an analog=20 gage) and the other for the ECM (which would later pass the signal onto=20 the dash). Only when they were rewiring and retooling the car to fully=20 use OBD II did they phase out the Gage sending unit. By 1996 all cars=20 "had" to meet OBD II requirements and by 1997 I think they finally began=20 using downstream o2 sensors on Saturns.=20

BTW it is Bla or Blah, not Blau.

No. Use Throttle Body cleaner, a toothbrush, and a soft clean rag.

Throttle Body cleaner works much better than ordinary carb or fuel injector cleaner.

Bob

BläBlä wrote:

Should i claen it with carb cleaner?

95 begin using two O2 sensors? (I havent been down there long enough under the 95 to notice if there was a downstream post-cat-converter O2 sensor).

There were TWO coolant temperature sensors on Pre-1996 vehicles and only one in Post-1995 vehciles. One sensor went to the dashboard gauge, whiel the other went to the computer. Thus it was possible to have the gauge read accurately while the fuel misture was enriched for a cold engine, EVEN THOUGH IT WAS WARM.

Hope this makes what was said more clear.

Bob

You're telling me something I knew already, Bob. :-) I'm the temperature sensor KING, yo! (I know more about the temperature sensors on 1994 Saturns than anything else - which I admit really aint that much) Blau Blau said 95 was a changeover year. Not being a mechanic I guess I misunderstood what a changeover year is. I would have thought *96* was the changeover year if they went to a single temperature sensor configuration in 1996. I discovered all by my little self what the function of each sensor was . I even went as far as to build a connector so that I could hook up to a digital ohm meter and measure the resistance "live" while connected to the vehicle.

Blau - Open Or High = infinate resistance or very high resistance in the range of Megohms. I've not seen one fail "shorted". If you were to short out the sensor, would the engine think its impossibly hot? Why not? The firmware apparently does not invalidate unlikely input! That is where I got the idea that it might be "shorted". The sensors I've seen go bad read such high resistance - leather would be a better conductor. And when the ECM sees 10 or 50 megohms resistance at the CTS does it think it's impossibly cold or does it consider the reading invalid? It apparently does the former.

On a hot day the over-rich mixture doesnt kill the engine, it makes it idle fast. I dont understand exactly why, but it does. Mine did.

Lets just say I'm completely wrong and you are correct. Mine are the only ones produced that do this. Out of a million Saturns, my two are the only ones that idle fast when the sensor is bad or high (or open - like when you DISCONNECT it) and everyone else's is different, I guess.

Shit, I missed the Twilight Z> What you said about 95 being a changeover leaves me scratching my

Bl=E4Bl=E4, sorry about the wrong spelling. I dont know how to make an "a" with umglots... If it makes you happy I'll cut & past it.

Oh - where is high or open? Its past the top of the page, WAY beyond

16,181 ohms...