Results on top are of current failure, bottom results are last smog test from two years ago. Only difference from then is I now have a new catalytic convertor, new O2 sensor, and new plug wires/plugs/cap/rotor. Did a compression test and results in order are 179, 182, 184, 189. Gas used then and now is 91. Anyone have any insight on why, with all else being equal, my car would fail even with a new cat and tune up? Smogman? Where are you?

EDIT:
D16Z6 block
D16A6 head
Si transmission
pre OBD components only.


Basically just used the Z6 block as a replacement, shaved head to compensate for piston dish difference.

 

How old is your new cat? What happened to the old one?
They take time to break in so if you JUST got it, then it would make sense.

Did you take time to warm up your cat by driving 20 or so miles before the test?
Did you have to wait long to test?
If you waited at short time, did you let the car idle to help keep the cat warm?

Also, did you get some cheap cat? They are not made the same.
Some use ceramic plates inside rather than the honeycomb.
Just like anything, if it costs less it's often due to the cheap material and they don't work as efficiently.

Don't test on 91 octane.
Use a lower octane to ensure a more complete fuel burn.
91 is pretty much overkill and useless in these engines. You are wasting your $ when you could just use 89 all the time.

 

Waited a week before testing on new cat, accumulated a little over 300 miles I believe. 26 mile drive from work to test, immediately on the dyno when I got there. Pretty certain that was warm enough (and punching it the last few miles before I got off the freeway). I don't know how you'd define a cheap cat, before the law change I stuck with CATCO hi-flow cats. Smog tech said the cat was doing it's job as evidenced by the NO levels. He said that HCs are unburned gas and yes next step was down grade fuel but he said that might not work because he was playing with distributor timing and that was the best he could get it. Definitely worth a shot before I open up my motor though. The thing that bugs me is that it passed just fine before. What could've possibly changed to make it fail?

 

possible injector sticking open, timming, O2 sensor, coolant temp sensor going bad, You are running rich

Pure Methanal will cover up HC but is just a quick fix... I think its 1 cup to one gal

 

Thanks for the insight, I'll be going to get a stethoscope after work today to listen to the injectors.

 

What octane fuel are you running? If your running 89/91 put in 87 just for the test. Your numbers weren't that bad so you may be able to pass if they give you a free retest.

 

Ignition timing checked?

Plugs properly gapped?

High fuel pressure?

 

Plugs gapped at .044, timing at stock mark 16 degrees yielded 140ish for HC, played with timing and that was the best it could get (I believe that is fully advanced). Stock fuel regulator is installed.

 

As already mentioned, run the gas tank low and then fill with 87 octane. Then use a timing light to set the ignition timing to spec. Are you following the service manual procedure?

What are the conditions of the plugs, wires, cap and rotor?

 

In the works right now for sure, still about a 1/3 tank left before I refill. Cap, wires, rotor, and plugs all new and used only for one week when that test was done. I snapped a pic of a plug last week, I'm uploading it right now...

EDIT: Added picture



All four of them looked like this after 300-320 miles or so, the original four looked nearly identical and they had roughly 6k miles.

 

Besides the emissions issue, does the engine have any performance problems at all?

Have you checked for an exhaust leak near the O2 sensor or a cracked header?

You also may want to measure the fuel pressure and test the FPR.

 

No performance issues at all, runs perfectly as far as I can tell. Still averaging 36-39mpg on Si/ZC gearing before I removed it to run normal Si gearing for smog (recommended by smog tech).

I'll have to look at the header later after work today. If you don't mind, can you elaborate how an exhaust leak may lead to higher HC readings?

For the fuel pressure I'll have to wait till the weekend and post up results.

 

An exhaust leak may allow air, which contains O2, to enter into the header. The O2 detected by the O2 sensor falsely tells the ECU that the engine is running lean. The ECU responds by increasing fuel to the cylinders, making the engine run rich.

 

I think that's the first time anyone explained anything in detail I had a question to LOL thanks!! I think you're on to something, I did notice a little "black" where the primary runners meet at the merge (2 piece DC header) when I was replacing my O2 sensor.

 

It's because your set up is too much of a beast for smog, lol. Sup man? Minmei giving you troubles again?
Sorry to hear that. Hit me up when your not too busy. Good Luck.

 

I went to your pad but I think your were out. Got a new phone, lost your number. Other car is totaled, need this one to pass ASAP. Using RX7 as daily, MPG no bueno.

 

Oh ****!! The white one got totaled? Sorry man. RX7 is definitely no bueno on gas. I just pm'd you my number.

 

Yep, team MPG is no longer...even though this car gets better gas mileage LOL

 

Update: Passed smog today. I did a few things to remedy the failure but the smog tech said that the thing that probably helped the most was having the injectors rebuilt.

 

 

Heard you passed too. Congrats.

 

Yup! Passed with failing colors, lol. Maxed out on the Hydro Carbons. The other readings were above average. Don't have to worry for another 2 years.