Emissions test failure

[mkoronowski]

My son's '90 SHO just failed emissions testing in Mass. with NOx a little too high. Here are the 5 different tests: The first test was on older plugs and 87 octane. Tests 2-5 were on new plugs.

HC= 0.95, 0.33, 0.32, 1.47, 0.24 gpm
HC limit=2.0
CO=18.06, 6.36, 7.44, 50.32, 8.90 gpm
CO limit=30.0
NOx= 3.58, 3.85, 3.93, 1.75, 3.72 gpm
NOx limit=3.0

I am being told we need new catalytic converters ( oh_my $$$)which bothers me. I thought NOx was due to high combustion temps caused by lean mixtures, hot plugs or things like that.

I'll take any suggestions .....what will happen with 93 octane, colder plugs, EGR valve...if there is one, O2 sensor...????????
[email protected] shrug
Thanks for the help! thumb

 

[Rob94]

Those numbers look close to my failure a few years back. Those idiots ALWAYS say it's the catalytic converters. I went to school with the kid who runs the shop where I get smogged, and he says that cats are rarely the problem. Try replacing the O2 sensors....it worked for me.

 

[Doug Waschenko]

From what I have seen, high NOX is an indication of catalitic converter failure.
When I put on a new set the car passes with flying colors.
The Ford head pipe with cats is around $1100. A better deal would be a high flow stainless set from Cincinatti SHO for $550.
Good luck.

 

[Mr Anonymous]

You're close enough to passing that a couple of new O2's, a can of Berryman's in the tank and some extended high-RPM driving may just get you under the wire to pass. Just make sure the Berryman's is run through completely and refilled with straight gas before the retest.

If you fail again, you could spring for the Catco y-pipe with cats for about $270, and even if that doesn't make you pass, once you spend over $200 in emission systems repairs for a car more than 10 years old you can go to the RMV for a waiver.

Here's some info on the Catco if you need to go that route: http://labwww.csv.cmich.edu/luke/auto/SHO/exhaust/

 

[mkoronowski]

Thanks for the advice so far. I'm embarrassed to admit that I'm this ignorant, but it sounds like a need help on a game plan. Also, to explain where I'm coming from.... I've got MD and can't help my son, so the garage has to handle parts replacement.

#1 Berryman's....auto parts shop hear we come.
#2 O2 sensors.... garage can handle this

?? plugs..... What brand? and do they come in different temp ranges?

?? plugs..... I think I've seen gaps 42 to 46
What gap do you run to cool combustion chamber down?

?? Intake filter..... Should it be new or dirty?

?? Octane.... 87 or 93? Which gets lower NOx

?? EGR...does the '90 SHO have and EGR system of any sort and what are the opportunities making changes?

Thanks again!

 

[Doug Waschenko]

Although this is contraversial, I think that if you lower your ignition advance you will raise NOX.
If you lower the octane and the engine pings on the machine, the knock sensor will lower the advance automatically.
Also if you have a lot of carbon build up in the combustion chambers you could be making the engine knock because of the higher compression and you may have worn valve guides with a lot of hardened oil on the top of the valves which you can only remove with the heads appart.
I think that higher unleaded octane is the way to go.
Try running some cat cleaner through the fuel.
Also the engine has to be at normal operating temperatures to run clean on the machine (this means hot, not cool),
Use the Ford SHO plugs only with a clean air filter.
Pulling the PVC hose won't help with the NOX only the HC (a little).
Sometimes the engine will go through on the third or forth try all by itself. The tech man has to want to get it through.
The cats need to be red hot to get clean.
If it doesn't clean up enough with all the little things, you need cats.
If the heads have all of the above problems, the new cats may not be enough either.