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My 900 2.0 turbo failed emissions test yesterday. I was just at the allowed level for HC and a little over on NOx, way under for CO. The guy at the shop that did the test said it may be a bad cat (car has 112k miles).

From reading the forums, it seems high NOx can be caused by high combustion chamber temps which is an indicator of faulty egr system. my question is, doed the 2.0 even have an egr system? I cant seem to find any info relating to an egr valve on a 2.0. If this is the case, what else should I check for before i go replacing the cat?

I did find that the vac line from the pcv check valve was disconnected from the throttle body. Could it be as simple as that? I know a loose vac line is a prime candidate for emissions problems, but I guess I feel that was too easy a fix and there must be something else wrong. any thoughts?
 

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A stuffed cat can raise the numbers for HC and NOx.

I fought with a Volvo 240 with this issue for a while and it ended up being the cat.

Edit: And no, with the exception of a small number of classic 900's, you will not find an EGR system on a Saab.
 

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Discussion Starter #3
hmmm... well, hopefully that disconnected vacuum line did the trick. I'm going to put that guaranteed to pass stuff in and try it again. if that doesn't work, hopefully i can find a used oem downpipe with a good cat for cheap.
 

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went back for testing today, and the car still failed. the readings were actually a little higher than last. HC and NOx still above test limits. anybody have any ideas before i order a 3" downpipe from jak? (I figured if i'm spending $$ I might as well upgrade).

More details on the car: I'm running an open air filter and mbc, althogh it doesn't seem like boost levels reach that high (stays in yellow) during the run on the dyno. I've also been losing a little bit of coolant, but can't seem to find the leak but i can smell it a little under the hood sometimes. There's no sign of oil in the coolant or coolant in the oil, and none of the plugs show signs of being steam cleaned. The plugs are fairly new and are the correct heat range (ngk's). finally, twice i noticed white smoke frome the tailpipe upon startup that smelled like oil shortly after i changed the oil. Think it could have fouled the O2 sensor? It hasn't happened again in over a week, so I assume I may have overfilled it. I have a turbo rebuilt kit ready just in case. Thanks for any info. With all the crap cars I've owned in the past, i've never failed emissions before.
 

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Coolant kills cats very fast. Since you said you had white smoke coming from your tailpipe ill assume your cat is done or dying, as white smoke is a strong sign of coolant entering the combustion chamber. If you have access to an osciliscope or scantool you can see whether your cat is working correctly or not by coomparing both your o2 voltages.

Does your car have any fault codes? Is the CEL on?

If so, Ill just throw some ideas out.

High HC's can be caused be leaky injectors, clogged air filter, misfires.

High NOx is caused by combustion chambers over 2500 degrees, and like you said, a faulty EGR which our cars dont have.

If you are failing for NOx you could be running lean. You are also failing for HC's you could have a misfire. If you put both together you have a lean misfire.

Lean mixtures are either a lack of fuel (clogged fuel filter, dirty injectors, low fuel pressure) or too much air entering the system (vacuum leak)

Its possible your o2 sensor could be fouled so you may want to check it out. If thats the case than the 02 sensor may be the likely problem. As I said earlier, a scan tool or osciliscope is the best way to verify the 02 sensor is working.

The vacuum line from the PCV to the throttle body wouldnt have much to do with this. All the PCV valve does is recirculate your crankcase gasses back into the combustion chamber to be burned.

Feel free to correct me if im wrong and if I remember anything else ill be sure to check back here.
 

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Discussion Starter #7
I don't think the white smoke was antifreeze as there was definitely a stong oil smell when it happened. I'll check the O2 sensor to see if there is any crap on it that shouldn't be. is there a better way to clean injectors than just running a can of stuff through the gas tank? I also have a new fuel pump on stand by in case mine fails, maybe I'll change it anyway.

I have a snap-on scan tool, but i think my obd connector is different for some reason. I'll have to check again. (my car is a 95). I also have a tech2 at my job, but unfortunately not the saab software for it. what sort of O2 sensor readings should I be seeing if it is working correctly? One of the guys at work had a friend who will pass my car, and while that may be ok for now, I still want to fix whatever is wrong with the car.

edit: there is also no CEL, and the light does work.
 

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Discussion Starter #8
so I talked to a saab tech today and he said the car is probably just running lean. he said to try a bottle of techron. he's used it on cars at the dealer and it seems to work well. he also said to check the cat look at the o2 voltages and the first one should fluctuate between 0 and 1 and the second one should stay steady. i checked them with the scan tool (it does work on my car) and they appear to be working properly, although the second sensor stays around .15 volts. is it a safe assumption to say the .15 volts indicates a working cat, but lean combustion? should this reading be closer to .5? i cant seem to find info on correct readings anywhere. if thats the case, then at least i know what my goal is as i try different things to fix the problem.
 

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not to dig up an old thread, but i figured i'd post my findings for when it shows up in someone's search.

I realized i have no 2nd o2 sensor since it's a 95. i dunno what theat second reading of .15 was on the scan tool.

anyhow, I installed a new 3" turboback from Jak the other day and when i peeked inside the old cat, the honeycomb was indeed shot, with a big hole right through the middle. looks like it just disintegrated. with the cat shot like that i'm surprised i was only slightly over the accepted readings.
 

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Ok so you figured out that the CAT was shot, and you replaced it. Now you need to find the cause of what caused the CAT to burn itself out, otherwise you really haven't fixed your problem, you've simply masked the problem.

Is the car running too lean? Does the engine have carbon build up on its internals? Is the ignition/timing/spark as it should be? How is the engines cooling system working, thermostat, radiator, ect. What about the oxygen sensor, MAF? All these possibilites can contribute to an increase in combustion chamber temperature which can cause an increase in NOx emission output.

Emissions troubleshooting can be complex, don't underestimate it.
 

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i know this thread is kind of old, but my 900 is also a '95 and my cel is on, i was just wondering what scantool you are using, is it obdII or obdI?
 
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