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Old 12-30-2009, 02:59 PM   #1
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Smile CEL, temp and fixes for a 900NG with a new owner

Ok, so I just bought this 1995 SAAB 900S 2.3L sedan. It had 178K miles. Information from this site and others have helped. Here is what I have and what I did fix.

First, when I got the car, it never warmed up. So, Immediately, I figure temp sensor. It also is eating a lot of fuel. I related the fuel consumption to the thermostat because if the car does not heat up properly, it will always run rich to warmup. Also, check engine light is on. Car also is a bit loud with the exhaust.

I had the thermostat replaced with an OEM original only, also to note as proved, that when it fails it fails in the open position. Now the car warms up fine and no troubles.
The car was sitting for some time and I was noticing a leak around the water pump area but could not pinpoint it. But, also after the car warmup and full pressurization of the coolant system, the leak stopped and is no longer losing any coolant.

Next, i had the front flex pipe replaced. It had the original pipe with a lot of corrosion and made a lot of noise. Now, I have a nice and quiet saab.

Check engine light is still on. So, I figure this is related to the fact that the previous owner did not fix the thermostat, and ran short trips less than 5 miles. So, I wanted to make sure I had the fuel system and engine clean. So, first I tried STP and other additives to the gas to clean the fuel injectors and fuel system. No notable changes.

Also, after start and on warmup, the car would run fine. In this first period of about 500 or more miles, I had a problem where after the car was warmed up and after driving a while, the car would rough idle or oscillate the idle attempting to maintain the idle. I tried a tank of premium also to help clean the engine out. I took the car on a long drive of 250 miles and on the highway it ran ok. Another 150 miles back and the idle problem was still there. I read many posts trying to see what it may be but did little to attempt a fix. I still wanted to make sure the engine and fuel system were clean.

No smoke out of the exhaust and the exhaust seemed normal. During this time I also changed the Automatic Transmission fluid as the original was old but not burned. Transmission shifted ok with a little bump on shifting. I drove 150 miles and had the transmission fluid emptied and refilled again. On this transmission the mechanic says there was no filter and the best thing was to empty and refill the transmission. Each time is about 3 quarts of fluid and the transmission holds around 7 quarts. So, I 've replaced the fluid twice, it shifts much better and I'll do the change one last time in about a month for one last drain and refill for this cycle.

Now, back to the CEL. I've used marvel mystery oil in my cars and really like it. I changed the engine oil with 0-30 synthetic mobil. That oil needed changing. I will not place additive into the synthetic, I don't think I need it and don't want to cause any problems. I also hear no strange noises from the engine so, I figure all is ok inside. But, I placed the marvel mystery oil in the gas. I used 8 ounces on the first full tank and have been adding 4 ounces to each tank filling. I was approaching 179K miles when I started this.

Within about 1/2 a tank, I noticed the engine began to run smoother. After warmup the occasional idling oscillation went away. So, also after reading these posts I also decided to try the OBD II diagnostic drive even though my year is not officially OBD II compliant and is considered OBD I. After performing start, Idle, runup and drive sequence, the car also seemed to run better. Then my MPG started to increase dramatically. Between 178K and 179K miles i was getting around 14 MPG to 18 MPG. Now, My MPG is climbing to 22-24 MPG. I just reset the indicator and it was showing upper 28MPG.

Not all results may be the same. I'm not sure if it was the MMM and/or the diagnostic driving sequence. I think cleaning out the engine and exhaust will take some time if dirty, Like I think this one was.

Also, My Check engine light started turning off on its own. In the beginning it would turn off when I first started the car. Then, after idling a while it would turn back on. So, I kept on driving. Several turn on and off sequences and my CEL is staying off more and more. Today, the CEL turned off and stayed off for a long period of time and my MPG is way up back to normal.

On another note, I am in the cold PA area right now. I have been using regular unleaded for the last 4 or 5 tanks. I tried premium but it was difficult to tell the difference in MPG with the other problems. Plus, with the very cold weather right now, I don't see the need for higher octane.

This car came from the south FL/GA area, moved up to the PA area in '05 and has been in this area since. The car is in very good condition and clean. I think it was well maintained by the original owners. It drives great for 179K miles.

Now, the car is running very smooth, idle is good, regular unleaded gas with 4 oz of marvel mystery oil added to each full tank.

I read a lot about the check engine light and I think in my situation it was started by the thermostat being broken open and the engine running too rich while always trying to warm up. The richness, I think, builds up carbon inside the engine and exhaust. After 1000 miles of long distance and fresh tanks of gas, and the MMM, I think i've solved my CEL problem and revitalized my SAAB. I wanted to share this story with you from a new owner.
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Old 12-30-2009, 03:10 PM   #2
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Quote:
Originally Posted by eagleye View Post

Check engine light is still on. So, I figure this is related to the fact that the previous owner did not fix the thermostat, and ran short trips less than 5 miles. So, I wanted to make sure I had the fuel system and engine clean. So, first I tried STP and other additives to the gas to clean the fuel injectors and fuel system. No notable changes.
Why not turn the key on and count the flashes?
http://www.saabcentral.com/~munki/te...s_motronic.htm
(looks like you jump the leads)

Quote:
Also, after start and on warmup, the car would run fine. In this first period of about 500 or more miles, I had a problem where after the car was warmed up and after driving a while, the car would rough idle or oscillate the idle attempting to maintain the idle. I tried a tank of premium also to help clean the engine out. I took the car on a long drive of 250 miles and on the highway it ran ok. Another 150 miles back and the idle problem was still there. I read many posts trying to see what it may be but did little to attempt a fix. I still wanted to make sure the engine and fuel system were clean.
Clean the Idle air controll valve.


Quote:
Now, back to the CEL. I've used marvel mystery oil in my cars and really like it. I changed the engine oil with 0-30 synthetic mobil. That oil needed changing. I will not place additive into the synthetic, I don't think I need it and don't want to cause any problems. I also hear no strange noises from the engine so, I figure all is ok inside. But, I placed the marvel mystery oil in the gas. I used 8 ounces on the first full tank and have been adding 4 ounces to each tank filling. I was approaching 179K miles when I started this.
Ease up on the mechanic in a can. You could really do more harm than good.

Quote:
Within about 1/2 a tank, I noticed the engine began to run smoother. After warmup the occasional idling oscillation went away. So, also after reading these posts I also decided to try the OBD II diagnostic drive even though my year is not officially OBD II compliant and is considered OBD I. After performing start, Idle, runup and drive sequence, the car also seemed to run better. Then my MPG started to increase dramatically. Between 178K and 179K miles i was getting around 14 MPG to 18 MPG. Now, My MPG is climbing to 22-24 MPG. I just reset the indicator and it was showing upper 28MPG.
Remove and clean the threads and head on your 1 o2 sensor, clean the threads on the pipe too.

Quote:
Also, My Check engine light started turning off on its own. In the beginning it would turn off when I first started the car. Then, after idling a while it would turn back on. So, I kept on driving. Several turn on and off sequences and my CEL is staying off more and more. Today, the CEL turned off and stayed off for a long period of time and my MPG is way up back to normal.
Cars don't heal themselves.

Quote:
On another note, I am in the cold PA area right now. I have been using regular unleaded for the last 4 or 5 tanks. I tried premium but it was difficult to tell the difference in MPG with the other problems. Plus, with the very cold weather right now, I don't see the need for higher octane.
Use low octane its not even a turbo, no sense spending the money Eurotech in Wilkes-Barre are good people.
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- pretend you are watering delicate plants...
Quote:
Originally Posted by SAABseanSCANIA
can be prone to failure due to increased localized stresses in the hole penetrations
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Old 12-30-2009, 05:46 PM   #3
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Yea, With the MMM, I just use one small bottle and then forget about it until problems reoccur, "mechanic in a can".

Well, I have been unable to get the light to blink. I connected the OBD II reader and I get power, but "no link" to the computer. Mechanic shop with OBD I had the same problem. "No link" I suspect I have to do some wire probing on the connector to make sure I have nothing loose.

My theory is that running the car on the highway eventually will burn the soot clean. Now, if there is a faulty sensor, then the problem will not get any better and may get worse. I chanced 1000 miles and it worked for me. with the exhaust seeming ok and not getting worse, I kept on driving. My original problem was an open themostat that didn't allow the car to heat to full operating temperature. the previous owner drove it with the open thermostat for how long, I don't know.

one other thing the previous owner and his mechanic did was connect a switch to disconnect the backup lights to pass an inspection, the claim was. All it was is a sticky backup switch. Thing was it took me some time to figure that the fuse the switch was disconnecting also disconnected the windshield wipers. The mechanic who installed the switch for $130 from the bill in the paperwork, was too lazy to replace the backup switch with a new one. The switch is working now, so I haven't replaced it yet.
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Old 12-31-2009, 12:29 PM   #4
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Yes, an OBD2 ready wont cut it, you need a paper clip.

The check engine light will flash a certain number of times.
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Quote:
Originally Posted by Delorean
- pretend you are watering delicate plants...
Quote:
Originally Posted by SAABseanSCANIA
can be prone to failure due to increased localized stresses in the hole penetrations

Last edited by Tweek's Turbos; 12-31-2009 at 12:32 PM.
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Old 12-31-2009, 12:30 PM   #5
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Retrieving the CEL Flash codes from a Motronic EMS.
The normally aspirated NG900's use a Motronic Engine Management System (EMS). When a Check Engine Light (CEL) shows, it indicates that there is a potential problem with the systems that are responsible for controlling the emmisions of the car. You can take it to the dealer and they will plug it into a computer to establish which part of the system is causing trouble, but if you want to get a rough idea of what the trouble is then you can use the following method.
On the kick panel underneath the steering wheel, and in front of the pedals, you will see a rectangular piece of plastic. This is the socket that the dealer plugs their diagnostic equipment into. Remove the cover and you will see that it has two rows of 8 connectors (See below)

1) Get a piece of insulated electrical wire and strip back the insulation about 5mm at each end. Insert one end of the wire into the socket for pin 6 (this is highlighted in red above)
2) Find a suitable place on the bodywork that you can ground the other end of the wire too (DO NOT ground it yet!)
3) Turn the ignition on and ground the wire for between 0.5 and 4 secs.
4) The CEL will now flash in two stages. Count the first set of flashes and then the second set. The two will make up the two digit number that you are looking for. e.g. 4 flashes followed by 1 flash equals 41.
5) Refer to the tables below to establish what the code means.
Motronic 2.10.2 (4 Cyl. engines)
Flash codeFunction
11Relay, secondary air injection
12No fault
21Mass air flow sensor
41Coolant temperature sensor
51Throttle position sensor
61Oxygen sensor
72Adaptation, long time
73Adaptation, short time
81EVAP canister purge valve
91Control module fault (RAM)
92Control module fault (ROM)
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Quote:
Originally Posted by Delorean
- pretend you are watering delicate plants...
Quote:
Originally Posted by SAABseanSCANIA
can be prone to failure due to increased localized stresses in the hole penetrations

Last edited by Tweek's Turbos; 12-31-2009 at 12:33 PM.
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Old 01-01-2010, 01:23 PM   #6
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Unhappy no link

Well, I'm going to have to now chase the wires because I cannot even get it to flash the check engine light. I suspect I'll have to follow that #6 wire and see where it goes and then ohm it out. No response when I short it to ground after turning the ignition on. I even tried pin #4 to pin #6 since pin #4 is supposed to be chassis ground.
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Old 11-07-2010, 10:31 AM   #7
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I have to revive this thread as I'm having the same problem not being able to pull the CEL codes. Have you diagnosed this issue? Thank
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Old 11-18-2010, 01:24 AM   #8
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Nope. I haven't chased it down yet. Too much wiring and not enough time to run all the wires.

Found my valve cover breather line hose very loose and not creating a good seal on the connections on the throttle body and the valve cover plastic splitter/connector. Replaced that and I thought my idle oscillating problem would go away. My favorite mechanic says that if it was the IACV then my problem would be too high a rev or not enough. So the IACV is working fine. With the age of the car, the oil going through the hose caused the hose to swell and the push on ends not to seal well causing vacuum leak for the valve cover breather.

I thought maybe my idle was fixed, but it's not. It doesn't seem to happen as much as before. It occasionally oscillated when I stop. It doesn't happen on startup. is only happens after the car is warm and I come to a stop somewhere. While idling, the idle oscillates. It's been suggested to check all the vacuum lines and I probably need to replace the old vacuum hoses now that I found one that was aged and worn out.

There is another very small vacuum hose connected to the valve cover breather hose. Since I guess hoses are cheap, I may start going around and replacing my old vacuum hoses that look pretty bad or are loose
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Old 11-18-2010, 08:39 AM   #9
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Bad IAC will cause hunting, at least on the turbo cars. Smack the IAC with a hammer when its hunting, if it settles down, there's your problem. Otherwise you have a cracked vacuum line somewhere.
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Old 11-23-2010, 03:00 PM   #10
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update to my CEL

Ok,

FYI '95, my engine 2.3L non-turbo. I pulled the airbox off. Real easy. Just a latch on the back. I found the Oil ventilator hose to be very loose, replaced that with a cooling hose that sealed good and gives adequate ventilation and doesn't collapse. My IACV is good and I didn't replace it.

Now my idling when warm has stabilized. I think the vaccum hose repair fixed this and it took some driving and fresh gas to stabilize it and run the engine clean.

Some of you don't like this, but it works for me. I used 1.5 times the recommended instructions of "Marvel Mystery oil" in my regular unleaded gas.

Since my car sat a while, I also went through the procedure to make sure the Emissions control was reset with the valuable driving sequence tip in the sticky on the main page. Then, after a 200 mile road trip, my check engine light went out. A fresh tank of gas, more Marvel Mystery oil as described and my MPG jumped from 16MPG to 33 MPG Highway and 27MPG city/local driving.

Check engine light is still off. I know one trigger that might turn my light on is heavy pedal acceleration and driving. When I'm easy on the pedal, the light would go off. It's been off for two tanks of gas and I'm a happy driver.

So, I blame the vacuum hoses first as the quickest thing to diagnose in the older cars. These hoses go bad over time and are very cheap to replace compared to other components.

I think marvel mystery oil does a very good job lubricating the injectors and cleaning the fuel path. several cars, also other than saab, which had a check engine Light, I recommend the MMM and the check engine light goes out when the problem is related to the dirty fuel we are all sold in the cars today.

I use about 6 ounces for 10 gallons instead of 4 per 10. So, this works for the fuel. I took care of the vacuum leaks. Though i could have some more smaller vacuum leaks in small lines I haven't found yet. But its all working good and the car is running well now with very good gas mileage.

Fortunately my sensors are all good so they are not creating a problem for my CEL.

One other point to mention is that when I first got this car, the former owner drove with the thermostat stuck open and the car running rich all the time. This was the first thing I fixed and I knew my injectors/valves and exhaust would be dirty with unburnt gas and sludge.

Now, in order to read the OBDII, I need to see where I might have a bad connection. I"m nervous about this but topics here have helped. I'll have to look behind the glove box at the computer connections. My problem is people say that just opening them up and some of the wires just fall apart or become disconnected. When I get into it, I want to be prepared to resolve what I can find.
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Old 06-25-2012, 05:46 AM   #11
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CEL update O2 sensor and driving sequence

OK,

I"ve got an update. Finally replaced the O2 sensor when My gas mileage when way low. My test was to change the system from "closed loop" to open loop with the disconnection of the O2 sensor. This caused my gas mileage to go up as the car entered "open loop" mode and used default values for engine management.

One thing. I did reset the Motronic and when I started the car cold, the check engine light came on before warmup. Now, I suspect this was the first indication of a problem with the O2 sensor throwing a flag. I also believe the oscillating idle was due to a weak oxygen sensor that was hunting the learn/rich mixture, one of the telltale signs of an O2 failure.

I replaced the O2 sensor, Mileage back up, check engine light still on. Mileage not as good as I'd like. I know I can get better. So, now I reset the motronic again on a fresh morning. This time, different behavior.

Warmup sequence good, no check engine light. But, as I move to the first accelerate mode, the check engine light turns on. This is the next flag that I have another sensor problem. So, if you track this, it may be possible to narrow your search of engine diagnostic problems with this sequence. So, my startup/warmup sequence was ok. But during the first acceleration, check engine light came on. So, I have found the list here somewhere and the tested items were Emissions purge valve, misfire, and fuel trim. I didn't hear any sort of misfire, car is running well, so lets hope fuel trim is good. So now I'm to the Emissions purge valve.

I"ve got to now sort through all the sensors related to this to see where the problem is. I did cycle though the whole sequence and my gas mileage is now way up from before, so I think a reset is important after changing out the O2 sensor.

BTW, before finding the O2 sensor, I found my SAI(secondary air injector) vacuum hoses were all disintegrating. I replaced them. Then found that my blower is probably not working, but does not throw a code, checkvalve to the exhaust checked ok. So, vacuum hoses can be a real hassle in these older cars as they break and leak. I hope the hose to the gas tank is OK.
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Old 07-04-2012, 12:08 PM   #12
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My control valve to the secondary air injection system was leaking, so I have disconnected the hole system, and plugged the hose the valve on top of the manifold.

If you have a leak here, you will suck in air to the exhaust system BEFORE the O2 sensor. This will trick the sensor to think your mixture is lean, and the ECU will boost up fuel, resulting in a rich mixture in the engine, but a perfect mix at the O2 sensor, causing carbon build up (my car), and a high fuel consumtion.
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Old 03-13-2014, 12:19 PM   #13
 
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Future reference, if Grounding the #6 pin does not produce flash code, you must jump pin #7 and #16, turn ignition key to on and I use a test light with an alligator clip to the door stop rod and the probe inserted into #6 for a second or two. Then Read the flash code. I get the 73 code often and usually pull the 30 amp #28 fuse for the computer for about ten minutes. I commute 120 miles a day 6 days so I don't get much carbon build up.
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