Failed Emissions Test - CO Levels high

[Kenny4d]

I just failed my emissions test yesterday with an extremely high carbon monoxide (CO) reading. Any advise on what I should do to get that reading down? why would it be so high... thanks.

[walawala]

What's your car? 8V? 16V? Bosch CIS K-jet or Electronic Injection (Lucas)?

Des

[Kenny4d]

Thanks Des...Sorry about that... I have a 1986 Saab 900 - 16V.

[ProfZ]

You have the Bosch LH 2.2 fuel system, with an airmass meter (AMM) that is adjustable. You can check this by disconnecting the AMM's harness plug and measuring the resistance between terminals 3 and 6 on the AMM with an ohmmeter (use a DIGITAL metr only). If you don't see 380 ohms, remove anti-tamper plug (on side of AMM near top) and adjust screw to get 380 ohms. If you can't get this value, the AMM is bad and must be replaced.

Also, the oxygen sensor might be bad (this is my first guess, actually). To test: Scrape a bit of insulation from the black wire coming from the sensor. Connect one probe of a voltmeter to the exposed bare wire, and the other to ground. Run the engine (it should be fully warmed up for this test). You should see a reading fluctuating around 0.5 volts. No reading, or no fluctuation, means the O2 sensor is bad.

Try these, and let us know what you get!

[Willy Wonka]

Had to set my 3-6 resistance to 225 to pass.

[Kenny4d]

How do you remove the anti-tamper plug on the side of the AMM near the top? Do I drill it out?
I haven't had a chance to get to the oxygen sensor yet but my current resistance test on the AMM (between terminals 3-6) reads 512 Ohms. Once I get the anti-tamper plug out, I will adjust the screw to read 380 ohms.

I'm going to test the oxygen sensor tomorrow after work.

Thanks

[Willy Wonka]

I usually drill a 1/8" hole 1/4" down and a coarse thread screw then use the drill with a screw driver bit to fasten the screw and pliers to spin the plug out.
There are other methods but this one works for me.

[cdaly]

Test the oxygen sensor first. Once it's initially set up, the system should be self adapting and the anti-tamper plug has a function after all.

Have you been through all of the vac hoses and such like first? Set up the timing correctly?

[Willy Wonka]

Yes he's right check it all first. Then if needed modify the resistance bridge level.

[Kenny4d]

I think I found the problem... The oxygen sensor signal is very weak .01 - .03. I will replace it over the weekend and retest on Monday... fingers are crossed!

What should my AMM resistance be reading? I have 2 1986 saab 900's - both 16 valve, and one reads 512 ohms and the other reads 943 ohms (between 3-6). Why would there be such a discrepancy in these readings and should I adjust them both to the same resistance?

Thanks

[eggsngrits]

Resurrecting an old post, sorry if it is annoying _

ProfZ- why a DIGITAL ohm meter for the AMM?


I barely failed carbon monoxide on my emissions test this morning. Any guidance is appreciated.

[RoccoH]

Because an ANALOG one could damage the fine electronic circuits inside...

[SaabFEVER]

my 84 8v wasn't passing eitherthen i bought fuel injector cleaner filled up the tank and what do you knowit works.

[Matthew]

I've heard too many stories of engine failure post use of injector cleaner. If the injectors need cleaning, then take them to a specialist. There, they'll be ultrasonically cleaned and flow tested. Good for another 20 years then!

[SaabFEVER]

its an old car and it wouldn't pass and i didn't have money to spend so i tried that and it worked.

[SaabFEVER]

anyway, what is the easiest way you guys have passed an emissions test?

[tek]

Controlling the "CO"
The CO (carbon monoxide) is one of the things that needs to be checked and set.
How to set it:

LH 2.2
Inside the AMM (Air Mass Meter) is a pot that controls the CO.
You can access this pot from the top.
To lower the CO turn counter clockwise, to rise turn clockwise.

If you want to verify the setting, disconnect the cable. Measure the resistance between pin 3 and 6 on the AMM.
A good value should be near 380 OHM

got this from the website http://www.900aero.com/

[escalator guru]

Originally Posted by SaabFEVER

anyway, what is the easiest way you guys have passed an emissions test?

Moving to a different state I've actually never had a car fail on emissions, but this AMM testing info will be pretty helpful while I'm trying to sort out that silly CEL I keep throwing.

[eggsngrits]

Originally Posted by RoccoH

Because an ANALOG one could damage the fine electronic circuits inside...

Yes, I should have consulted the Bentley first. I'm going to try some other tweaks before messing with the AMM.

Thanks to all.

[woywitka]

Originally Posted by Matthew

I've heard too many stories of engine failure post use of injector cleaner. If the injectors need cleaning, then take them to a specialist. There, they'll be ultrasonically cleaned and flow tested. Good for another 20 years then!

interesting matthew. my saab mechanic said he reccomends running a bottle thru before emissions. i have yet to do it, i don't care for additives, to many very different opinions.