Catalytic Converter

[BigMo82]

I have been having issues with a rough idle and white smoke for months now. The white smoke wasn't visible for the last few months as the weather warmed up but it's been back this week. The idle has never really got any better.

I went to a friendly local Toyota specialist who did a diagnostic check today and told me that the waveform from the upstream and downstream O2 sensors are the same which would indicate that the catalytic converter is not working. He explained that the upstream signal should be up and down and the downstream waveform should be a near flat line. My question is could a bad CC cause a rough idle and smoke? I have attached a video if the rev counter when the car is idling.

Mo

trim.QVVenf.MOV

[waqar_lionheart]

BigMo,

I wouldnt class that as really being erratic idle or rough idle. That looks more like something kicking in i.e. a fan or some other kind of device. Did you have anything on at the time but i have seen fair share of bad idle rpm and this doesnt even come close. I hope that puts your mind at ease. As far as white smoke is concerned, if there isnt any coolant loss (bar the acceptable coolant loss) I wouldnt be concerned about it at all. As soon as the cold snap has come, my car is giving off a little white puff as well. This is just condensation and soon clears up after few mins of driving as soon as the car gets up to temperatur really. I used to worry about it as mine is 1.8vvti as well but i have stopped now. I have done some research about o2 sensors as mine two pre cats were out and had been out for many years and my car was running quite lean ( it only recently stopped knocking due to lean mixture issues. Whole other story). From what I have read, if cat efficency was low (cats dont bust so easy) the O2 sensor would pick it up and report a cat efficiency below threshold DTC but IF the O2 sensor had any circuit issues or anything like that it reports a heater circuit malfunction DTC. If it failed to heat up properlyat startup, it would register a heater circuit malfunction DTC. So in my opinion if it didnt send any signal it would be DEAD :). I hope that this would put your mind at ease. I am not sure if wave form would or should differ as its the potency of the voltage that tells the ecu if there is an issue. I think most sensors send a 5v signal and that alters if something is outside the specified range but I AM NOT SURE ABOUT WAVE FORM.

Regards,

Waqar

[BigMo82]

Waqar thanks for the detailed reply, The rough running is manageable but the amount of smoke I get is definitely not right. I drove the car last night. The temperature was 17C and even after a 20 minute drive I wasn't upto temperature and still had smoke.

Mo

[Parts-King]

If the car does not warm up after 20 miles it would suggest the thermostat is stuck open, if that happens the car runs cold, worth taking it out and inspecting it

Kingo

[BigMo82]

Thanks Kingo, I have been thinking about doing this for a while but not sure how to get to it. I can carry out simple tasks like removing the throttle body and rocker gasket but never dealt with a thermostat before

[VTTI]

It could be the 02 sensors, a mechanic friend of mine said Toyotas are known for 02 sensor problems which in extreme cases could kill the cat.

[BigMo82]

There was a downstream O2 sensor that was faulty and that came up with an EML. The sensors resistance was checked which I did myself and confirmed it was faulty and it was changed over and ever since I've never had another management light come up.

Mo

[waqar_lionheart]

Hi BigMo,

In your original post, you didnt mention that it doesnt warm up as expected. I have followed your posts where you had swapped out the throttle body with the ones from breakers which also turned out to be faulty. Anyways, what i am trying to say is that I think Kingo is spot on it might be your temp sensor is stuck. If it is stuck in a position where it thinks that the engine is still cold, it might be making your car run rich. if so then you could also get smoke due to overfuelling. How is ur MPG? I would take out my spark plugs and see if its running rich, lean or adequate.

Best of luck.

Regards,

Waqar