Smog help help help!!!!!(high importance)
08-29-2002, 07:33 PM
#1
Burning Brakes
Thread Starter
Smog help help help!!!!!(high importance)
Hi all,
I failed my smog test!!!!!!!
My NOX was through the roof.
My last smog test in Canada had all my readings in the green and now in California, my readings are nuts.
Something must have failed or gone seriously wrong since my last smog check.
In 1999 my tests showed the following
CO% = 0.01
HC ppm = 87
NO ppm = 379
Canadian RPM = 1291
On the Canadian test, there is no %CO2 or %O2
Canadian test only has one RPM at 1291 along with dilution of 13.9??? maybe this is %CO2??
Canadian test has no readings for wheel speed or the 1248RPM testing.
As you can see, I would have been in according to these numbers but only marginally with respect to HC ppm.
Now my most recent readings
At 15mph / RPM 1364
CO% = 0.01-----------limit 0.80
HC ppm = 117---------limit 128
NO ppm = 3287!!!!----limit 1127
________________________________________________
At 25mph / RPM 1809
CO% = 0.00-----------limit 0.60
HC ppm = 31----------limit 103
NO ppm = 2201!!!!----limit 987
Something's not right here. That NOX reading is crazy? I have fixed a bunch of stuff since my last smog test and the car runs like a champ since I've fixed things.
It does have a set of Auto-Authority Chips in it but they were there on the Canadian test too?
Everyone, please put your thinking caps on. I have one month before my Canadian registration runs out and if I don't get this fixed, I will be posting on the Fiero Forum while my shark sits under a cover.
Please help.
BTW - The ref scared the crap out of me. He said "where is your engine management indicator". Huh??????
A few calls later and he finally confirmed for himself that my MY did not have a bloody "check engine soon" light. That was a 45 minute process while I sat and sweated it out for awhile.
I really need you all on this one.
A big
Cheers
Bernie
I failed my smog test!!!!!!!
My NOX was through the roof.
My last smog test in Canada had all my readings in the green and now in California, my readings are nuts.
Something must have failed or gone seriously wrong since my last smog check.
In 1999 my tests showed the following
CO% = 0.01
HC ppm = 87
NO ppm = 379
Canadian RPM = 1291
On the Canadian test, there is no %CO2 or %O2
Canadian test only has one RPM at 1291 along with dilution of 13.9??? maybe this is %CO2??
Canadian test has no readings for wheel speed or the 1248RPM testing.
As you can see, I would have been in according to these numbers but only marginally with respect to HC ppm.
Now my most recent readings
At 15mph / RPM 1364
CO% = 0.01-----------limit 0.80
HC ppm = 117---------limit 128
NO ppm = 3287!!!!----limit 1127
________________________________________________
At 25mph / RPM 1809
CO% = 0.00-----------limit 0.60
HC ppm = 31----------limit 103
NO ppm = 2201!!!!----limit 987
Something's not right here. That NOX reading is crazy? I have fixed a bunch of stuff since my last smog test and the car runs like a champ since I've fixed things.
It does have a set of Auto-Authority Chips in it but they were there on the Canadian test too?
Everyone, please put your thinking caps on. I have one month before my Canadian registration runs out and if I don't get this fixed, I will be posting on the Fiero Forum while my shark sits under a cover.
Please help.
BTW - The ref scared the crap out of me. He said "where is your engine management indicator". Huh??????
A few calls later and he finally confirmed for himself that my MY did not have a bloody "check engine soon" light. That was a 45 minute process while I sat and sweated it out for awhile.
I really need you all on this one.
A big
Cheers
Bernie
08-29-2002, 08:04 PM
#2
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Bad cat? Perhaps an extended rich running condition may have toasted it.
Your NOx numbers are off by an order of magnitude it seems.
Whenever I go for a smog check, I change the oil the day before, then take the car on a run at high RPM's to get everything good and hot. While waiting to enter the station, leave the car running. This wouldn't have helped you in this instance though.
Your NOx numbers are off by an order of magnitude it seems.
Whenever I go for a smog check, I change the oil the day before, then take the car on a run at high RPM's to get everything good and hot. While waiting to enter the station, leave the car running. This wouldn't have helped you in this instance though.
08-29-2002, 08:16 PM
#3
Burning Brakes
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Hi Bernie,
There is product called GTP (Guaranteed To Pass). Use it for, if I recall correctly, most of a tankful. Heat up engine, and try the test again. You have nothing to lose in taking the test multiple times. Follow Randy's advice too.
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" />
There is product called GTP (Guaranteed To Pass). Use it for, if I recall correctly, most of a tankful. Heat up engine, and try the test again. You have nothing to lose in taking the test multiple times. Follow Randy's advice too.
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" />
08-29-2002, 08:35 PM
#4
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Check w/ you smog shop about how many times they can test the car. Last I checked, CA's smog tests are on a central network to Sacramento, so They know the results pretty much right away. If you fail repeatedly you can get gross polluter status and pay an extra fine for registration and renewals. When the results are uncertain, make sure the tester gives your car a trial run before the real deal. Good luck, and welcome to the Golden State!
08-29-2002, 08:45 PM
#5
Burning Brakes
Thread Starter
Hi Guys,
Last night I filled the tank and added "bardhal" emissions pass fluid to the tank. Ran like a MF for about 100miles. Changed the oil at 11pm. Went home and hoped for the best. Referee doesn't really give you many options. Car was off for approx. 1/2 hour before dyno. Had to be off while he went through all the visual inspections so couldn't do much there.
Referee said that high NOX is not indicative of a bad cat. Something to do with high combustion chamber temps. I think he said.
So all that advice, as good as it is, doesn't appear to be my problem.
What about the o2 sensor?
My curiosity is over the fact of how much my NOX went up since my last test? It would appear to me that something has failed somewhere.
Keep posting please!!!!!
I need to track this down and fast.
I really appreciate evryones input and I will try whatever it takes.
BTW - If I take the car to a Porsche dealer, would they be able to diagnose any failed components that would cause this?
Also, is the fuel/air mixture on my MY adjustable or is it computer managed as well.
I have already been pegged a "Gross Polluter" by this test. I can retest as many times as I like or care to pay for. Problem is that after Sept., I will have no registration whatsoever
Cheers
Bernie
Last night I filled the tank and added "bardhal" emissions pass fluid to the tank. Ran like a MF for about 100miles. Changed the oil at 11pm. Went home and hoped for the best. Referee doesn't really give you many options. Car was off for approx. 1/2 hour before dyno. Had to be off while he went through all the visual inspections so couldn't do much there.
Referee said that high NOX is not indicative of a bad cat. Something to do with high combustion chamber temps. I think he said.
So all that advice, as good as it is, doesn't appear to be my problem.
What about the o2 sensor?
My curiosity is over the fact of how much my NOX went up since my last test? It would appear to me that something has failed somewhere.
Keep posting please!!!!!
I need to track this down and fast.
I really appreciate evryones input and I will try whatever it takes.
BTW - If I take the car to a Porsche dealer, would they be able to diagnose any failed components that would cause this?
Also, is the fuel/air mixture on my MY adjustable or is it computer managed as well.
I have already been pegged a "Gross Polluter" by this test. I can retest as many times as I like or care to pay for. Problem is that after Sept., I will have no registration whatsoever
Cheers
Bernie
08-29-2002, 09:17 PM
#6
Chronic Tool Dropper
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Bernie:
One of the few things that directly affects NOX is ignition timing too far advanced and some detonation as a byproduct. The Autothority chipset advances the timing slightly to give a little more snap off the line and through midrange. In the literature that comes with the chipset they warn you about detonation and pinging, and especially tell you to run premium gas. For competition driving like DE events, you are supposed to use race gas.
So-- first step would be to check the ignition timing, and try setting it at the lower end of the allowable range. If the timing is set by the brain box as mine is in the S4, the only way to adjust it is to pull the Autothority chipset out and plug the originals in, at least until you pass the test. You will also want to try at least a partial load of race gas (look at Unocal's website for a race ga$ station nearby) and/or add a couple bottles of octane booster to get your numbers good again.
After that, as Randy points out, the cat may be fouled/failed, and not helping your cause any. Interesting that, with plenty of extra torque on tap, we often fail to notice deterioration in performance until it's pretty serious. A little ignition weakness sends a puff of unburned fuel to the cat, which dutifully reacts it before passing the air out the back. Gain a little heat each time, until the coating is damaged and no more NOX management.
I pulled the chips and did a couple shots of 104+ last time to get mine to pass on NOX, after it just barely failed the first time. It passed fine after that, and I am casually looking for a set of ZIF (zero insertion force) sockets for that chipset to make swapping a little easier.
For those following along at home, NOX is produced when chamber temps exceed a critical value, something in the 2500 degree range IIRC. Way back when NOX was discovered to be a serious smog villian, we were strapped with low compression engines, exhaust gas recirculation, thermostatic ignition retard, etc, all in the interest of reducing combustion temps. Modern engine management does a lot of the work now, but there are still plenty of engines that come new with EGR and less-than-perfect ignition maps, all thanks to NOX problems. The Autothority chips try to take advantage of some of the conservative headroom designed into the factory ignition maps, but may, undr certain circumstances, push you over the line a bit.
Hope this helps you on your way!
One of the few things that directly affects NOX is ignition timing too far advanced and some detonation as a byproduct. The Autothority chipset advances the timing slightly to give a little more snap off the line and through midrange. In the literature that comes with the chipset they warn you about detonation and pinging, and especially tell you to run premium gas. For competition driving like DE events, you are supposed to use race gas.
So-- first step would be to check the ignition timing, and try setting it at the lower end of the allowable range. If the timing is set by the brain box as mine is in the S4, the only way to adjust it is to pull the Autothority chipset out and plug the originals in, at least until you pass the test. You will also want to try at least a partial load of race gas (look at Unocal's website for a race ga$ station nearby) and/or add a couple bottles of octane booster to get your numbers good again.
After that, as Randy points out, the cat may be fouled/failed, and not helping your cause any. Interesting that, with plenty of extra torque on tap, we often fail to notice deterioration in performance until it's pretty serious. A little ignition weakness sends a puff of unburned fuel to the cat, which dutifully reacts it before passing the air out the back. Gain a little heat each time, until the coating is damaged and no more NOX management.
I pulled the chips and did a couple shots of 104+ last time to get mine to pass on NOX, after it just barely failed the first time. It passed fine after that, and I am casually looking for a set of ZIF (zero insertion force) sockets for that chipset to make swapping a little easier.
For those following along at home, NOX is produced when chamber temps exceed a critical value, something in the 2500 degree range IIRC. Way back when NOX was discovered to be a serious smog villian, we were strapped with low compression engines, exhaust gas recirculation, thermostatic ignition retard, etc, all in the interest of reducing combustion temps. Modern engine management does a lot of the work now, but there are still plenty of engines that come new with EGR and less-than-perfect ignition maps, all thanks to NOX problems. The Autothority chips try to take advantage of some of the conservative headroom designed into the factory ignition maps, but may, undr certain circumstances, push you over the line a bit.
Hope this helps you on your way!
08-29-2002, 09:35 PM
#7
Burning Brakes
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Oops,
Sorry that I did not know anything about the California laws. Can you regain good citizen status with good results?
The last car that I had to not pass had a throttle body type of carburetor. The air filter container was not mating tightly with the top of the carburetor. There were other inputs to the air filter area that were leaking. I fixed the air leaks, did a normal tune-up, and it passed. I have no knowledge of your symptoms, just things that worked for me. There are all of those rubber sleeves on your intake manifold and MAF. They could be leaking. When this happened to me, I could not get the RPMs to go slow enough to even contemplate a test on my 928. There are also many vacuum elbows, spider, and an X connector to harden with age, and leak. I really do not know if that would cause your symptoms.
A dealership should be able to fix your problems, and get it to pass. Are you close to DEVEK? If so, see if they (or anyone that works on this) have equipment to diagnose your problems, solve them, and test emissions. You may be able to get them to run the emissions test in “test” mode. That way the results don’t go to the DMV until you go “live.”
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" />
Sorry that I did not know anything about the California laws. Can you regain good citizen status with good results?
The last car that I had to not pass had a throttle body type of carburetor. The air filter container was not mating tightly with the top of the carburetor. There were other inputs to the air filter area that were leaking. I fixed the air leaks, did a normal tune-up, and it passed. I have no knowledge of your symptoms, just things that worked for me. There are all of those rubber sleeves on your intake manifold and MAF. They could be leaking. When this happened to me, I could not get the RPMs to go slow enough to even contemplate a test on my 928. There are also many vacuum elbows, spider, and an X connector to harden with age, and leak. I really do not know if that would cause your symptoms.
A dealership should be able to fix your problems, and get it to pass. Are you close to DEVEK? If so, see if they (or anyone that works on this) have equipment to diagnose your problems, solve them, and test emissions. You may be able to get them to run the emissions test in “test” mode. That way the results don’t go to the DMV until you go “live.”
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" />
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08-29-2002, 11:43 PM
#8
Burning Brakes
Thread Starter
Hi Thom,
Thanx for the post.
And welcome Dr. Bob, I was hoping you would jump in here.
OK lets look at your posts:
It would be nice, albeit expensive if it was the CAT. Change it, retest and go home happy. But- the referee didn't think the cat would cause the high NOX. Is he just not hip to these cars or is he out to lunch? Cannot advance timing on MY85. I still have the original chips - somewhere? so I will definately put those back in.
I should also state that 92 octane fuel is not available in my area so I have been running 91. Should I have used octane boost prior to testing?
If someone was to make a list of probable causes and prioritize them, what would they be???
Thanx Guys
Thanx for the post.
And welcome Dr. Bob, I was hoping you would jump in here.
OK lets look at your posts:
It would be nice, albeit expensive if it was the CAT. Change it, retest and go home happy. But- the referee didn't think the cat would cause the high NOX. Is he just not hip to these cars or is he out to lunch? Cannot advance timing on MY85. I still have the original chips - somewhere? so I will definately put those back in.
I should also state that 92 octane fuel is not available in my area so I have been running 91. Should I have used octane boost prior to testing?
If someone was to make a list of probable causes and prioritize them, what would they be???
Thanx Guys
08-30-2002, 12:07 AM
#9
Burning Brakes
Thread Starter
Jiminy Christmas!!!!!
A rebuilt cat for my car at 928Inter. is $1000.00!!!
I don't have that kind of bread to throw at a cat. Gulp..... I hope its something else.
Anybody have one that I could borrow until I pass the test? Then I will test pipe the thing until the next smog test or I win the lottery.
Thanx
Bernie
A rebuilt cat for my car at 928Inter. is $1000.00!!!
I don't have that kind of bread to throw at a cat. Gulp..... I hope its something else.
Anybody have one that I could borrow until I pass the test? Then I will test pipe the thing until the next smog test or I win the lottery.
Thanx
Bernie
08-30-2002, 12:30 AM
#10
Three Wheelin'
Bernie, you don't have to spend that kinda money on a cat.
For my 86.5, MK industries has a dual cat bolt-on replacement complete with forward pipes for about $350.00
There should also be some generic cats which can be welded to your existing pipes by an exhaust shop.
I'm due for cats, but I'm still looking for a better deal than MK ind., but I like the idea of MK's simple pipe and cat "bolt-on" solution.
Greg
For my 86.5, MK industries has a dual cat bolt-on replacement complete with forward pipes for about $350.00
There should also be some generic cats which can be welded to your existing pipes by an exhaust shop.
I'm due for cats, but I'm still looking for a better deal than MK ind., but I like the idea of MK's simple pipe and cat "bolt-on" solution.
Greg
08-30-2002, 12:34 AM
#11
Burning Brakes
Thread Starter
Thanx Greg,
The hairs on the back of my neck are starting to come down a bit now. whewww....
Hopefully, its not the cat at all. Maybe just something else expensive. Have you got a web address for these guys?
I'm lurkin' here like a shark guys. Keep 'em comin'
Bernie
The hairs on the back of my neck are starting to come down a bit now. whewww....
Hopefully, its not the cat at all. Maybe just something else expensive. Have you got a web address for these guys?
I'm lurkin' here like a shark guys. Keep 'em comin'
Bernie
08-30-2002, 12:59 AM
#12
Three Wheelin'
Hi Bernie,
http://www.mkindustries.com
I did a archive search and found a jewel of a thread about cat's started by John S. and "piled on" by a number of regulars, past and present. A MUST READ!! Some of the comments are a hoot!
http://forums.rennlist.com/cgi-bin/r...14&t=000647&p=
If you have the original 18 year-old cat, chances are you need to replace it.
Greg
http://www.mkindustries.com
I did a archive search and found a jewel of a thread about cat's started by John S. and "piled on" by a number of regulars, past and present. A MUST READ!! Some of the comments are a hoot!
http://forums.rennlist.com/cgi-bin/r...14&t=000647&p=
If you have the original 18 year-old cat, chances are you need to replace it.
Greg
Last edited by Greg86andahalf; 07-15-2003 at 03:51 AM.
08-30-2002, 01:14 AM
#13
Burning Brakes
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Hi Bernie,
Some more useless information for ya’. You can advance the timing. I would not want to go there. DEVEK has a video that you can rent. It requires removal of cam covers, dial indicator from say Harbor Freight, special indicator rigging and clamping, interpretation of the ambiguous factory video. Dr Bob has a world of knowledge beyond mine on this subject. If you return chips to factory spec, and do a normal tune-up, you are back to a level playing field.
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" />
Some more useless information for ya’. You can advance the timing. I would not want to go there. DEVEK has a video that you can rent. It requires removal of cam covers, dial indicator from say Harbor Freight, special indicator rigging and clamping, interpretation of the ambiguous factory video. Dr Bob has a world of knowledge beyond mine on this subject. If you return chips to factory spec, and do a normal tune-up, you are back to a level playing field.
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" />
08-30-2002, 01:25 AM
#14
Chronic Tool Dropper
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[quote]Originally posted by Bernie:
<strong>Hi Thom,
Thanx for the post.
And welcome Dr. Bob, I was hoping you would jump in here.
OK lets look at your posts:
It would be nice, albeit expensive if it was the CAT. Change it, retest and go home happy. But- the referee didn't think the cat would cause the high NOX. Is he just not hip to these cars or is he out to lunch? Cannot advance timing on MY85. I still have the original chips - somewhere? so I will definately put those back in.
I should also state that 92 octane fuel is not available in my area so I have been running 91. Should I have used octane boost prior to testing?
If someone was to make a list of probable causes and prioritize them, what would they be???
Thanx Guys</strong><hr></blockquote>
Start with the chips, as they will do a world of good on their own. Finding them?? If your garage is like my new one is now, it might take a while. My 928 stuff is still living in the other garage for a while, thank goodness. Anyway, that's a first step.
Next is some octane booster. Two bottles of 104+ is a double-dose in a 20 gal tank, should be enough to tame the explosions for a bit.
I'm not familiar with the chemical makeup of any of the 'guaranteed to pass' additives, but at this point they are certainly worth a try.
Half a tank of 100ish race gas is about $40, good investment if you have a station somewhat close by. Not such a great deal if you waste most of it on the drive home from the gas station. Try the station locator at <a href="http://www.76.com." target="_blank">www.76.com.</a> I'll paste in the URL from my session, may or may not work for you:
<a href="http://www.76.com/cgi-bin/b2cpt01/scripts/mapQuery.jsp?BV_SessionID=@@@@0054180595.1030680836@@@@&BV_EngineID=cccd adcgddkidiicfimcemndhhgdgjg.0&Tool=locate&Site=76#" target="_blank">http://www .76.com/cgi-bin/b2cpt01/scripts/mapQuery.jsp?BV_SessionID=@@@@0054180595.1030680836@@@@&BV_EngineID=cccd adcgddkidiicfimcemndhhgdgjg.0&Tool=locate&Site=76#</a>
or call their station locator line at 1-800-345-0076 and aks where you can get it close to you.
The cat is a 'maybe' option, a last resort. Since you already have the luck to be labelled a gross polluter, you will be visiting at least a test-only station, and maybe a referee, for the rest of the car's life. It also means that you have nothing to lose except the test fee to try the simpler stuff before you spring for a cat. The cats are three-way cats, in theory. They work to cut down on HC, CO, and NOx in that order with different reactive sections for each pollutant. If you find that you can't pass, try to borrow a cat from somebody on the list. More than a few folks have installed test pipes and have the old cat gathering dust. I saw a post somewhere in the last few days with a later cat changing hands for $20-- a lot less than a rebuilt one from Jim, and a little easier to swallow especially if it turns out to not be a cure.
Let me know how you do with this. There's a 76 race gas dispensary in Pasadena a few miles east of me here, if you get in a bind. It's still 70 miles from where you are though. Gotta be a place closer to you!
<strong>Hi Thom,
Thanx for the post.
And welcome Dr. Bob, I was hoping you would jump in here.
OK lets look at your posts:
It would be nice, albeit expensive if it was the CAT. Change it, retest and go home happy. But- the referee didn't think the cat would cause the high NOX. Is he just not hip to these cars or is he out to lunch? Cannot advance timing on MY85. I still have the original chips - somewhere? so I will definately put those back in.
I should also state that 92 octane fuel is not available in my area so I have been running 91. Should I have used octane boost prior to testing?
If someone was to make a list of probable causes and prioritize them, what would they be???
Thanx Guys</strong><hr></blockquote>
Start with the chips, as they will do a world of good on their own. Finding them?? If your garage is like my new one is now, it might take a while. My 928 stuff is still living in the other garage for a while, thank goodness. Anyway, that's a first step.
Next is some octane booster. Two bottles of 104+ is a double-dose in a 20 gal tank, should be enough to tame the explosions for a bit.
I'm not familiar with the chemical makeup of any of the 'guaranteed to pass' additives, but at this point they are certainly worth a try.
Half a tank of 100ish race gas is about $40, good investment if you have a station somewhat close by. Not such a great deal if you waste most of it on the drive home from the gas station. Try the station locator at <a href="http://www.76.com." target="_blank">www.76.com.</a> I'll paste in the URL from my session, may or may not work for you:
<a href="http://www.76.com/cgi-bin/b2cpt01/scripts/mapQuery.jsp?BV_SessionID=@@@@0054180595.1030680836@@@@&BV_EngineID=cccd adcgddkidiicfimcemndhhgdgjg.0&Tool=locate&Site=76#" target="_blank">http://www .76.com/cgi-bin/b2cpt01/scripts/mapQuery.jsp?BV_SessionID=@@@@0054180595.1030680836@@@@&BV_EngineID=cccd adcgddkidiicfimcemndhhgdgjg.0&Tool=locate&Site=76#</a>
or call their station locator line at 1-800-345-0076 and aks where you can get it close to you.
The cat is a 'maybe' option, a last resort. Since you already have the luck to be labelled a gross polluter, you will be visiting at least a test-only station, and maybe a referee, for the rest of the car's life. It also means that you have nothing to lose except the test fee to try the simpler stuff before you spring for a cat. The cats are three-way cats, in theory. They work to cut down on HC, CO, and NOx in that order with different reactive sections for each pollutant. If you find that you can't pass, try to borrow a cat from somebody on the list. More than a few folks have installed test pipes and have the old cat gathering dust. I saw a post somewhere in the last few days with a later cat changing hands for $20-- a lot less than a rebuilt one from Jim, and a little easier to swallow especially if it turns out to not be a cure.
Let me know how you do with this. There's a 76 race gas dispensary in Pasadena a few miles east of me here, if you get in a bind. It's still 70 miles from where you are though. Gotta be a place closer to you!
08-30-2002, 02:13 AM
#15
There's a bunch of stuff that could potentially cause the car to fail the test. Cats would be at the bottom of my list. As I see it, cats are there as a last resort, to try and clean up a mess that's caused by another problem elsewhere in the engine. A car that runs well with everything working as it's supposed to should pass the test even without any cats. Cats may help you pass a test, but they're not correcting the real problem.
The timing change that Thom was refering to above is for the cam timing, not the ignition timing. The only way that the ignition timing can be changed on your car is with aftermarket chips or an aftermarket computer system.
Assuming that all of your basic tune up type stuff is in order (caps, rotors, plugs, coils, plug wires), there are still some things that can cause you problems with the test. At least some of them are:
Bad temperature sensor
Bad O2 sensor
Bad mass airflow sensor
Bad wiring or bad connection at or from one of the above sensors, or in the ignition system
Dirty or bad fuel injector(s)
Bad fuel injection or ignition computer
Disconnecting the battery for a little while to reset the computer couldn't hurt either. Let the car idle for maybe 10 minutes after you reconnect the battery.
Sorry I couldn't be more specific and give an exact definite solution, but I'd say look into new cats as a last resort.
The timing change that Thom was refering to above is for the cam timing, not the ignition timing. The only way that the ignition timing can be changed on your car is with aftermarket chips or an aftermarket computer system.
Assuming that all of your basic tune up type stuff is in order (caps, rotors, plugs, coils, plug wires), there are still some things that can cause you problems with the test. At least some of them are:
Bad temperature sensor
Bad O2 sensor
Bad mass airflow sensor
Bad wiring or bad connection at or from one of the above sensors, or in the ignition system
Dirty or bad fuel injector(s)
Bad fuel injection or ignition computer
Disconnecting the battery for a little while to reset the computer couldn't hurt either. Let the car idle for maybe 10 minutes after you reconnect the battery.
Sorry I couldn't be more specific and give an exact definite solution, but I'd say look into new cats as a last resort.