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Discussion Starter #1
some help here guys would be greatly appreciated! so i failed emissions again on my 1991 saab 900 turbo and its the same deal as two years ago when i failed. My NOx is too high. last year i took the test twice and failed and paid my mechanic two different bills. after the second fail, he took it personally to a test center (i have never heard of a mechanic doin this before) and it passsed, but i looked the papers fron to back: the cap on NOx is 1750 ppm and my car passed with 1747!!!!! i do not know what my mechanic did, and now two years later my car is failing with flying colors, that exhaust gas must be really hot. to my understanding nitrogen oxides are forming in my 4 combustion chambers because temp past ignition is too hot? and for this reason exhaust gas is too hot? any help would be greatly appreciated, i need to pass emissions on a budget! I love my car more than anything i have ever owned and want to take it with me back to college this year. what can or should i do?? thanks all for tips!
 

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It isn't really temp of exhaust gas, there is too much localized hotspot in the cylinder that are really hot...

what are the other numbers? If the HC/CO is very low maybe you can turn the distributor the other way and pass :p
 

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some help here guys would be greatly appreciated! so i failed emissions again on my 1991 saab 900 turbo and its the same deal as two years ago when i failed. My NOx is too high. last year i took the test twice and failed and paid my mechanic two different bills. after the second fail, he took it personally to a test center (i have never heard of a mechanic doin this before) and it passsed, but i looked the papers fron to back: the cap on NOx is 1750 ppm and my car passed with 1747!!!!! i do not know what my mechanic did,
as in slipped the inspecting station guy $40? :cheesy: That would be my guess...
and now two years later my car is failing with flying colors, that exhaust gas must be really hot. to my understanding nitrogen oxides are forming in my 4 combustion chambers because temp past ignition is too hot? and for this reason exhaust gas is too hot? any help would be greatly appreciated, i need to pass emissions on a budget! I love my car more than anything i have ever owned and want to take it with me back to college this year. what can or should i do?? thanks all for tips!
Are you running premium or regular? IIRC, NOX values with premium were very slightly lower, and if you are on the line that may help. (I deal mostly with truck diesels, and we often find putting BIO in them gets it through emissions!)
 

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A failing/old AMM will show high Nox, as will elevated engine temps (you could try a cooler t-stat). I have read/ heard that heavy deposits on the intake valve-stems can raise Nox too. PHipson touched on a method I used before I was any good at fixing Saabs, dilution; give the sniffer more of something its not looking for like a fuel tank with three gallons of premium gas and a high dose of ispropyl-alcohol (good old fashioned dry-gas.), then top off the tank right after the test.
 

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Discussion Starter #5
ok so a few things. first off i always have run mid grade gas in the car, this is what the mechanic has told me to do. even tho i know that the apc is a great little computer and can deal just fine with normal gas, atleast that is the siide of the debate that i stand on!! here are the numbers so you can get an idea of the magnitude of the situation:

HC limit:150
my saab:80
CO limit:.80
my saab:.15
NOx limit:1750
my saab:2579

that NOx is a pretty big jump.
work i have had done LAST emissions- 2 YRS ago:

first: i failed emissions
second: brought to mechanic he did the following:cleaned fuel injectors set ignition timing
third: i failed emissoins
fourth:brought to mechanic and he did the following: checcked O2 sensor-lean conndition-swapped air mass meter from another car to fix readings. cleaned intake manifold.
fifth: MEChanic took to emissions and passed with only 3 ppm's on NOx!!! he told me i shoudl get a new or used AMM too!
so this is the situation, is the AMM really the culprit for high NOx that is failing by such a huge margin!
one last thing, i heard of sea foam to run into the gas tank should i run that through my car to clean inner parts out and make it happier? thanks for all and any help! happy saabing
 

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Seafoam will help with everything downstream of the AMM. Do NOT try to test with seafoam in the fuel. You will really fail again. run it through, and be ready for some smoke from the pipe and other things if you have a build up on the Cat and heavy build up anywhere. thoroughly use the tank of seafoam, run atank of fresh gas, THEN go test. Another AMM or cleaning it with throttle body cleaner can't hurt either.
 

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Discussion Starter #7
hey guys so i wanted to run something by you more skilled folks! i was told by an ex mechanic that i can pass emissions with my nox levels high if i throw 2 bottles of dry gas into a full gas tank and run her hard for a long trip and then bring it straight to the test. can anyone concur on this? will this make me fail other things (the HC and CO) or will this even work? he didnt say i needed to run the dry gas completely out of my system, so is this agreeable? thanks and happy saabing!!
 

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hey guys so i wanted to run something by you more skilled folks! i was told by an ex mechanic that i can pass emissions with my nox levels high if i throw 2 bottles of dry gas into a full gas tank and run her hard for a long trip and then bring it straight to the test. can anyone concur on this? will this make me fail other things (the HC and CO) or will this even work? he didnt say i needed to run the dry gas completely out of my system, so is this agreeable? thanks and happy saabing!!
typically putting alcohol in the tank can make it pass, dry gas is generally methanol plus a cosolvent

don't get rid of all of it just go for the test
 

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What he said. Or try a qt of 91% isopropyl alchohol from Wallgreens/CVS/whoever.
 
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