Another sho fails emissions, cats?

[zuup_2000]

I just got this jalopy running, and it failed emissions badly.
------------on the 25/25 test----------
HC-ppm 114 allowed, reading was 183 Failed
CO-% .63 allowed, reading was .56 Passed
NO-ppm 796 allowed, reading was 2754 Failed bigtime
-----------------on the 50/15 test-----------------
HC-ppm 117 allowed, reading was 187 Failed
CO-% .65 allowed, reading was .57
NO-ppm 879 allowed, reading was 2922 Failed bigtime

The car is running great, no idle sugring, no ignition problems, so I figured it must be the cats. I ran both KOEO, and KOER tests, and I didnt get any problem codes. Can bad cats make that much of a difference?
I believe the cats are original, w/162,000miles, if they arent the original ones, they are still really old looking (rusty, etc..)

The car has new plugs/wires, I had the top end apart to do the upper 60K, but the guy that rents the tools couldnt get them in time for me to do it. I measured the clearances, and all of the clearances are within spec. I replaced the injector O-rings, and grommets. All new gaskets, and no vacuum leaks.

The car has new O2 sensors, along with just about every other sensor that can be changed out (cam sensor, coolant temp sensor, etc...)

Does this sound like the cats? I know I can pull the spout, but will it make up for that huge NO number its giving.

The car is a 1992 MTX

 

[Russsho]

Yep, that sounds like cats.

 

[zuup_2000]

I figured it was, but I didnt think they would make that big of a difference. I went ahead and ordered the Catco Y-pipe last night, and now I need to inspect the cat back system. Ill go ahead and put the new Y-pipe on, pull the spout, and cross my fingers.

 

[Troglodyte]

Definitely sounds like the cats aren't working at all. I just redid my emissions (NM) last month. And even with a bad Cam and CPS sensor and a leak at the throttle body (forgot to fully tighten one of the bottom nuts ) I passed easily.

HC-11
CO-.07
NO-Less than 40 (no measurable reading)

Cats make a huge difference, the guy who did my emissions quipped that he's seen new vehicles off the lot with worse emissions than my car.

 

[zuup_2000]

Well, I pulled the Y-pipe off and found out that the cats have been gutted. I guess it explains the problem with passing emissions.

 

[SeanMc]

Nice!! I just got back from a muffler shop to find that my rear cat is empty and now resting nicely in my mufflers, while my front one still has some honeycomb in it, but the rest is sitting nicely in my mufflers. The car putters, stutters, gives a temporary CEL, and here is one that threw me off, it gave me an ABS light tonight after it sputtered and almost shut off. It could be a combo for me, gas, ?cps? (car starts just fine hot or cold and doesn't throw a code..so hopefully not), and bad cats. I'm moving more towards that it's exhaust related. Doug Lewis Y-pipe ($579 +shipping), and DynoMax catback ($279), and LPM (Ted B./Vadim $?) this month. Yay, expensive month! What sucks even more is that I need my car for work, and it needs to be smogged and registered by 12/17. So these next few weeks are going to be working for the car, no longer the man.

 

[Dan H]

Pulling the SPOUT will make a large difference in NO as it reduces combustion chamber temperature. Also, the hotter the cats are, the more they will help reduce NO. Make sure they are fully heated up before testing. The HC is obviously due to the gutted cats.

 

[zuup_2000]

Just FYI incase someone comes across this thread with the same problems,

I had the emissions test done again today. I did nothing but replaced the Y-pipe with a catco unit, and had the same fuel in the tank, and did not pull the spout connector.

These are the new readings, and as you can see, it passed without a problem. You can compare these numbers to my original numbers to see what difference the cats made.
------------20/25 test--------------
HC-ppm- 114 allowed, reading was 007
CO-%-.63 allowed, reading was .01
NO-ppm-796 allowed, reading was 010
CO+CO2-%- 6.0 min, reading was 15.4
------------50/15 test---------------
HC-ppm- 117 allowed, reading was 006
CO-%-.65 allowed, reading was 0
NO-ppm-879 allowed, reading was 010
CO+CO2-%- 6.0 min., reading was 15.3

Like I said, the only change made was installing a new Y-pipe w/cats (standard flow, replacement). One less problem to worry about.