My friend has a 2000 SiR (which is equivalent to an American Si, B16 engine) and he failed the emissions test. (scan of it below)

Before the test he drive the car around and got it nice and hot and made sure they took it straight away. Plus he put methyl in with the gas so combustion was cleaner. And he still failed. The Co% and No pm are fine, he is just failed on is HC.

And there is no CEL ( unless he pulled the bulb/burnt out) according to the law here a car which is throwing a CEL cannot be tested.

Other stats:
- when he purchased the car the numbers were almost zeros
- Has installed header, intake and aftermarket cat (will get specifics on this)
- burns about a litre of oil every 5000-7000km
- "The car has been doing one odd thing lately, it will backfire or pop in the exhaust on occasion between shifts. could that be affecting it in some way?"
- has Honda tick (valve clearance adjustment needed)
- It has also been suggested he is running rich and needs a tune


Anyway he is gonna dick around with it this weekend and any suggestions to help him woudl be appreciated.

Scan of his etest:

 

The backfiring suggests that the ignition timing is off. Use a timing gun to check the timing with the service connector jumped.

Adjusting the valve clearance would also probably help.

 

Since it is aftermarket CAT, I don't have much faith in them. They are an inferior product compared to Honda. The backfire should be fixed first and the primary O2 sensor can cause a problem. I had O2 sensor go bad that will cause HC to fail even though it doesn't throw out a CEL.