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Discussion Starter · #1 ·
Hello Saab world,
This is my first Saab (1987 900s) and I need some help. I understand that this car is almost older than I am but I experience cold start problems. In the morning when i get in my car, I have to hold the RPM's at 1000-1200k for about 5-10 minutes or the RPM's drop below 800 and the engine dies. It always does this...everyday even if it is cold out or not. I am not sure of what maintainence has been done, but the engine runs fine once it warms up fully. I also try to drive the vehicle after only warming it up for acouple of minutes and notice that I have little to almost no power at all. I can put the pedal to the floor and it feels like im going nowhere. I just need help with suggestions as to what can cause these problems. Any help would be appreciated, Thank you
 

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Could be the NTC sensor. It senses the temperature of your engine coolant. They are cheap and easy to replace. It sits right below the intake manifold. Blue sensor with a 2 pin plug. There is a method to test it that involves heating it up and observing resistance changes, but it costs less than $20, so I just replace it if I question it.

Since it's your first 900, I'll be the first to suggest buying the Bentley service manual. It is a very good starting point for maintenance and troubleshooting. It's available on Amazon.
 

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Discussion Starter · #3 ·
I checked for a "NTC" sensor and cannot find anything...is there another name for the sensor? if you can quickly explain to me why a faulty sensor (NTC sensor) would cause my vehicle to act up like this? thank you for your time
 

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You probably want to look it up as a water temperature sensor. It measures the water temperature at the intake manifold and is used by engine management to adjust how rich or lean you can run during cold start and hot start. A failure of this sensor can provide a bad (hot or cold) indication to the computer, and depending on how it failed, either make you too rich after warm-up, or too lean at cold start.
 

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You will need to drain some coolant before you take that sensor out. About a gallon is plenty. Easiest way to drain it is from the radiator drain. Right side near the battery. You'll need a 1" deep well socket to open the drain. I just stick a piece of cut-off garden hose over the drain and into my clean drain pan so I can reuse the coolant. When you're done with the job and ready to refill the coolant, there is a bleeder port on the thermostat housing. Crack it open and refill until coolant comes out that port.
 

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It can be expensive throwing parts at a problem. There is a test for the coolant temp sensor described in the Bentley manual.

One of my 900s is a little cranky while warming up (idle falls, engine stalls) and it's a faulty AMM (diagnosed the most reliable way, by swapping a good one in from my other 900). One day I will get it fixed but it settles down in about 30seconds so not a huge problem. Five minutes would be a nuisance.
 

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Don't confuse the man. The water temp sensor is the nail connector in the front of the head and sends a signal to the water temp gauge in the dash. This has nothing to do with the fuel mixture on warm-up. The NTC sensor although indirectly sensing water temperature should not be described as one. It can be very confusing for the less informed. The NTC is the blue device situated between the two centre pipes of the inlet manifold. Test it. Engine cold about 2500ohms. at normal engine temperature it should be 320ohms for Bosch NTC. It seems likely that this is your problem, given the symptoms you describe.

You don't need to drain any water when replacing this. As long as you keep the reservoir cap on you will lose less than 1/2 pint water.
 

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Discussion Starter · #13 ·
No I'm not threatening to do anything...I'm just implying that I am interested in selling my vehicle either way, but I need to fix things first.
 

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NTC = Negative Temperature Coefficient (sensor) Probably not your problem. At least in my case the NTC sensor didn't present symptoms until AFTER the engine got hot. My sensor wasn't bad; it was just a bad connector. Cleaning / wiggling fixed it.

Check the FAQs on this forum: http://www.saabcentral.com/forums/showthread.php?t=62123 There are articles there on idle problems, starting/stall problems, and NTC sensor problems.

There's also a list of Saab acronyms; http://www.saabcentral.com/forums/showthread.php?t=119183
AMM = Air Mass Meter

Also check here under applicable headings: http://townsendimports.com/Web/
 

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Don't confuse the man. The water temp sensor is the nail connector in the front of the head and sends a signal to the water temp gauge in the dash.
More accurately, that's a sender.

The NTC sensor although indirectly sensing water temperature should not be described as one.
Tell the guys that wrote Bentley; they call it the coolant temperature sensor.
 

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I would be scrutinising the idle valve for sticky/laziness, the throttle plate stop and throttle position switch for correct idle sensing at throttle stop...... as well as black wires tethered at the top of the head, above the thermostat for good secure connections.

Sadly, this is not an easy 2 minute task but one that needs to be assisted with the knowledge of how to use a multimeter and electrical diagnosis techniques.
As suggested, this can be expensive if some understanding of the fuel system is not taken on board.


Best advice as written above, obtain a copy of the Bentley manual.
 

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I just read re NTC in Bently last night , ( bed time Novel...lol ) they do call it a coolant sensor ... then later down the paragraph reference NTC and expand the acronym < also dtailing expected resistance values at Given temps .

Its Hard to confuse the 2 .. Called whatever .. One is at the front of the head near the thermostat ( a sender ) the other is located between injectors ... ( a sensor )


The sensor ..

Its name , its function and its location are clearly spelt out by RAUB in the initial response , no confusion there .

My experience is that issues here (NTC) are more likely to show on a warm/hot engine ( incorrect resistance reading enriches fuel mix , effectively flooding ) , not my experience but no doubt the reverse can be true ( too lean from incorrect reading ) .

Regardless one way to eliminate or prove .. Test the resistance comaper it to Pevas figures ( or bently's) .. Or if you are happy throwing parts . Thro away
 
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