Some basic info on my car:
- 165,xxx miles on the chassis
- Engine rebuilt about 26,000 miles ago (no porting done, basic rebuild)
- Sequential twins and all emissions intact
- Stock ECU
- Stock intake
- HKS DP
- Stock main cat
- Cat back

My FD has always passed smog with flying colors with everything I mentioned above. I havent installed any new parts or removed any parts since my last smog check 2 years ago. Today I took my car and my sisters FC to get smogged. Her's passed without problems and mine failed the pretest because its running too rich.

Heres the results:

HC ppm: Reading: 182 Limit: 88
CO %: Reading: 1.42 Limit: 0.52
CO2 %: Reading: 13.2
O2 %: Reading: 0.9
NO (x) ppm: Reading: 234 Limit: 704

P.E.F.: 0.468

Any idea what I can do to lower these readings? In a possibly related note, my car has developed a surging while stopped when the car is in gear with the clutch in (like at a stop light). It usually does this before getting up to operating temp and rarely does it while fully warmed up. It wont surge if the car is idling with the tranny in neutral. Only if its idling with the tranny in gear and the clutch pressed in. I havent had a chance to look into it since I drive it about 2-3 times a month and havent had much free time lately to work on it.

I need to fix this so I can pass smog before the end of December. Thanks!

 

Could be a bunch of things, but spark plugs would be my first guess. How many miles on them?

 

Based on how high it is above passing, do you have an aftermarket pulley?

I think sometimes the sensors in your rats nest just go haywire, we tore apart/re-double checked everything that could have caused me to run rich and came up with no answers.

Except I was running 900 HC and passing here is under 100 for 30 seconds.

Swapped the Pettit Pulley and it brought it down to 780, but eventually we just went with a power fc and tuned it down. Dunno if any of that helps. GL.

 

How many miles on the stock cat? That may need replacement.

 

The spark plugs may have ~1,500 miles on them.

No aftermarket pulleys here. The only mods I have are posted in my original post. I wish I had a PowerFC right now so I can lean things out just to smog it but Im running on the stock ECU.

If the cat was never replaced by a previous owner, it would have 165,xxx miles on it. I've never replaced it so I dont know if its the same one it left the dealer with or if it was ever replaced by the dealer at some point in its life. The smog guy told me to check the inlet and outlet temperature of the cat. He said a general rule of thumb is that the outlet should be twice as hot as the inlet. If not, the cat may not be bad. Being that it was a Test only station, they dont have a lift so we couldnt test the cat there.

 

Unfortunately if the cat is that old, it might have lost most of it's potential to do its job.

 

Have you verified that your airpump is functioning?

 

Just some thoughts...

-Looks like your reduction catalyst is working (the one that lowers NO), but there may be some issues with the oxidation catalyst (the one that converts HC, CO to H20 & CO2), or you're simply running too rich and even the stock cat can't save you...

-I currently have an ignition problem (last couple months) and know for certain that I run a little bit richer than normal, my gas milage has suffered, and power has dropped off... make sure your ign is working properly, if you have been feeling any breakup on the top end you may want to pay particular attention to that. I'm fairly sure I don't have other issues (bad compression, excessive oil consumption)

-Make sure your air injection is working properly (per Majik)...
*all the hoses are intact, clamps are solid
*ACV is working (vacuum signals actuate the passages properly, the ACV I had was initially sticky until I cleaned it up!)
*air pump actually pumps air, it's plugged in
*check valves working properly (one in the ACV is for port air, shouldn't be a problem when on the rollers and car is warm, another is close to the CAT and if exhaust gas can somehow get back upstream or interrupt the flow of air to the CAT you may have problems with lowering HC/CO)
*and that your connections are stout (there are several gaskets and bolts, one for the ACV-->LIM, another for motor-->split air pipe (to cat), another split air pipe-->check valve on CAT, and also from motor-->air pump relief (shouldn't make a difference))
*There's also a switching solenoid that controls the port/split air for the ACV/cat you may want to check...

-If you need another stock cat to try out, I have one you can borrow. It's supposed to have <50k miles on it, and I managed to pass /w PFC just a few months back.

-Judging by your CO readings you're running rich (as you already know), the question is, by how much? Do you have a WBO2, if so what are your AFRs when on the rollers?

Good luck dude, I know what you're going thru!

 

there's supposed to be a way to jumper the airpump circuit at the fusebox so that it pumps air at all times. Should help

Go to the West forum, theres tons of tips there.

 

I'm sure you thought of this already, but I would check fuel pressure before taking anything apart, if it's excessive then fix that first. Could be a faulty regulator, bad vac signal/cracked/loose hose, bad fuel pulsation damper, faulty injectors, etc. etc.

 

OR PM DJDino to get rid of the smog head ache

 

Your idle problem is likely being caused by a bad clutch switch. Here's how to fix it:

https://www.rx7club.com/3rd-gen-archives-73/cheap-bastard-fix-clutch-switch-495391/

This may or may not effect your smog problem.

 

Doh!, in July I had the same massive emissions failure with my '94 Rx7. It only has 44k miles on it too. I had always passed emissions. Now I'm way to rich. I previously owned another 3rd gen that had only 85 PSI per rotor. But it always passed emissions. My psi per rotor is just over 100. In frustration, I removed the rat's next and pulled the injectors. I tested all my solenoids and had the injectors cleaned. KGparts said that the injectors barely needed cleaning. So much for that approach. I replaced my plug wires. I found that one had burned up within the leading coil. Therefore, I replaced the leading coil along with the wires. All these preventive measures made my '94 Rx7 much more responsive.
I brought it back for reinspections and failed with the overly rich issue again.
According to MDPalmer's post above there are about a million different things that could cause emissions failure. I'd just start throwing $$ at it. Worked for this guy who bought a new OEM cat. Very expensive. I just bought one too from Malloy Mazda. Only $1,600. Next I'll get a new engine and throw it in.

The guy at JPR imports told me to test my air pump by unpluging it while the car is idling. If the idle turns rough then you have a good air pump. No one seems to be able to pin point the reason why the 13b start running excessively rich.

 

From my own experience:

I was able to pass emissions with a cat that had 163,000+ miles on it and an engine with over 100,000 miles, so it is possible (and that was with a downpipe/NO precat);

I agree the airpump and ACV, etc. could be a potential problem and should be checked;

The O2 sensor should be replaced if it's high miles. The tests are run closed loop and the sensor will affect it;

In order to pass (at least for my car) the tests have to be performed in 1st and 3rd. If 2nd gear is used, the rpm's are too high for the 2nd test and the air pump is cut off by the ecu. The result is similar to the rich condition you've described; and,

There is a vacuum line on the FP regulator that goes to a solenoid and then manifold vacuum. It is used to reduce FP to compensate for manifold vacuum and to raise pressure for hot start situations, etc.. As mentioned above, it should be checked--this can be done indirectly by measuring the fuel pressure as described in the FSM.

Hope this helps.

 

I'd like to thank everyone for their input so far. I havent had time to mess with my car yet due to work but I'm going to make time to check everything out. I'll make sure to keep you guys updated on my progress. Thanks

 

Just wanted to update this thread in case someone has this same problem in the future.

I installed a brand new oxygen sensor along with new spark plugs (I'm getting ready for a track day) and did nothing else to the car. I passed the smog test and it looks like the o2 sensor was the culprit. I'm good to go for another 2 years! I'm glad it was an easy fix. Thanks to everyone for your replies

 

good to see u found the issue.

the question of underdrive pulleys and smog was brought up earlier in the thread. i saw this thread yesterday it made me wonder if i would be able to pass california emissions since i'm running the pettit main underdrive. well i took the fd to smog today and it passed okay. other relevant mods.. downpipe.

i did have one problem though.. i had the car lowered to about 24.25 inches all around from ground to fender/quarter panel arch and at this height.. when the rear end was lowered onto the rollers the exhaust piping contacted the ground and ended up melting a doormat that was sitting on there , and i was worried that the piping/exhaust hangers may be damaged. i raised the rear up 1 inch and afterward the clearance was fine. so anyone with a lowered fd planning on doing smog at a place with in ground smog roller machine should raise that rear up a bit.. lol