Celica Forums General Discussion Engine and Performance Cannot solve emissions problem. HELP!

Hi,
I have a Japan imported Toyota Celica TRD 2001. (This is similar to the GTS). Some history about the problem:
I bought it 2nd hand around 6 years ago. It always ran fine but on the first Vehicle-Roadworthy-Test (VRT, not sure what they call it in your country), it failed emissions test. The catalytic converter needed replacement together with a lambda sensor.
2 years later, the lambda sensor was busted again, and changed it in order to pass VRT.
Another 2 years passed and same problem. Changed lambda sensor again, but it wasn't enough as apparently the catalytic converter got busted again! So I took it again to the local Toyota auto dealer and for the past 6 months they've been trying to find out why this is happening.
This is what they've tried so far in these last 6 months
- change catalytic converter with original one together with lambda sensor (minor improvement but not enough)
- cleaned injectors (minor improvement but not enough)
- swapped petrol pump from another TRD (now it starts immediately rather than stuttering but no effect on emissions)
- changed ECU from another TRD and here it gave a false positive. Emissions were back to normal and we thought we had solved the issue. So they took it to VRT the next day, and it failed emissions again because it was running bad again!
- they now tried a new set of injectors (no effect)
- they tried changing the rails (no effect)

Do you have any suggestions on what we could try?

Thanks for your time.

Use a spark plug non non fouler and steel wool or other spacer on the down stream O2 sensor to pass.

Hi @Shammy. I will forward your info as I'm not a mechanic. But this sounds like a hack rather than a proper fix. Does your suggestion actually turn down the emissions?
If there's something wrong with the car that's failing the O2 sensor and also the catalytic converter every couple of years, it needs to be fixed.
When Toyota replaced the catalytic converter they told me it was totally busted, even though I had replaced it a couple of years back.

It is a hack, not something a mechanic will do for you.
Is your car otherwise driveable?

If so, it will allow you to keep a car on the road for about 10$.

Hi @Shammy. Thanks for the tip.
It is perfectly drivable otherwise. I doubt Toyota will actually do the hack.

My friend mechanic also just told me about some chemical to clean up carbon that gets clogged in the ports/valve. Only problem with this is that for the chemical to work, it needs to be driven. But I cannot drive it as I need to get the license in place first. Or otherwise open up the engine and clean up the manifold etc. Do you think that could help the strange issues of my car?

I am not optimistic it will help.

What do you mean by failed emissions, are you receiving DTCs?

Hi @Shammy, when I say failed emissions test, I'm referring to the road-worthy test that we need to do in our country. They stick a sensor in the r's silencer and check the emissions are within range. It's called VRT here but might be called something else in your country. We have to do it every 1 or 2 years (depending on car age).