1999 Yaris, NCT emissions fail

jonerkinsella

Hi.

I rallied the crap out of it on the way in

The car has 103000 miles. Driving great but emissions are through the roof on the first test and retest.

Results,

Low idle = CO 8.76 vol%
(580 rpm ) HC 672 ppm.

High idle = Lambda: 0.90
(2.770 rpm ) CO 3.55 vol%
HC 263 ppm .

Any ideas lads ?

Thanks.

Atlantic Dawn

Your way over the limits, is the car burning any oil or have a bluish smoke coming from the exhaust. When was it last serviced? Have you checked the exhaust for any leaks?

Special Circumstances

Does it idle and run ok?

jonerkinsella

Atlantic Dawn wrote: »

Your way over the limits, is the car burning any oil or have a bluish smoke coming from the exhaust. When was it last serviced? Have you checked the exhaust for any leaks?

No. Last week . No exhaust leaks.

jonerkinsella

Special Circumstances wrote: »

Does it idle and run ok?

Running perfect. No spluttering till it hits the rev limiter in every gear.

jonerkinsella

Could it be the maf ?

shietpilot

Pre-cat O2 sensor? You need to plug in diagnostics and see how the sensor waveform looks on live data

jonerkinsella

I have to get my hands on a diag now ��

selectamatic

Make sure the car is reaching operating temperature if the thermostat is stuck open it'll be running cold and rich

jonerkinsella

selectamatic wrote: »

Make sure the car is reaching operating temperature if the thermostat is stuck open it'll be running cold and rich

The engine cold light is coming on blue and going out when warm within about 3 mile. The engine was definitely warm when doing the Nct. I drove it in hard and the test started within 5 mins of parking outside.

visual

How often are you topping up the oil.

jonerkinsella

visual wrote: »

How often are you topping up the oil.

Serviced just before nct with oil and filters. P

selectamatic

First port of call would be air filter, clean throttle body, check plugs and leads, ensure there are no fault codes present when the car is hooked up to diagnostics, then finally a dash of diptane and a few good long drives if the car doesn't pass after all that I'd be very surprised but if it didn't then it might be time to consider a new cat.

shietpilot

selectamatic wrote: »

First port of call would be air filter, clean throttle body, check plugs and leads, ensure there are no fault codes present when the car is hooked up to diagnostics, then finally a dash of diptane and a few good long drives if the car doesn't pass after all that I'd be very surprised but if it didn't then it might be time to consider a new cat.

Dipetane will do nothing when the car failed the emissions so badly I think

selectamatic

shietpilot wrote: »

Dipetane will do nothing when the car failed the emissions so badly I think

Probably true if diptane was the only thing done but I suggested using it along with a number of other maintenance checks all in the hope that the car would pass the emissions test without having to shell out for a new cat. Diptane is a fierce job for helping with emissions but it's only as good as the supporting work allows for. Firing diptane into a tank and hoping for the best is pot luck at best, but that's not what I recomended.

jonerkinsella

So far ... I have tested the o2 sensor with a meter and it is functioning well within specs (12.7ohms , http://my.prostreetonline.com/2015/02/20/dtc-p0141-how-to-test-a-corolla-oxygen-sensor/ ) . I have lashed a load load diptene into the tank . I inspected the plugs and they are perfect (installed 3500mls ago , the 4 plugs look anywhere from picture 16-19 here ,http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html ) I have also cleaned the maf ,it was slightly oily.

Today I am going to thoroughly inspect the exhaust system for micro cracks ,as that is all I can think of now. The car has a retest on Thursday morning.

punisher5112

My guess would be o2 sensor or cat so probably that.

selectamatic

Make sure you do plenty of driving between now and then and burn the tank with diptane in it. Diptane raises the emissions at first it's only when it's been completely burned through the system that emissions reduce, so try to be on your second tank post diptane when going for test

jonerkinsella

I forgot to check the rear cat sensor. I tested it earlier and found it to be totally dead . I had to drive all over the south east this morning and eventually got a working one (just as well I brought my multi meter. one breakers tried to sell me two totally dead ones that where bent from crash damage telling me they worked fine + another I went to collect was off an Avensis with different fittings ) .

I have fitted the new sensor and reset the ecu by disconnecting the ecu cables under the glove compartment .

I'll let you lads know what happens in the retest.

jonerkinsella

Car flew through the nct this time after the sensor change.

Thanks for all the suggestions lads.

Till next year

shietpilot

So the only thing you changed was the rear O2 sensor (post cat)? My Yaris also failed the NCT and coincidentally the rear O2 sensor is also dead. I guess that's probably the cause of my issues too! Toyota must be using the rear sensor for calculating the fuel ratio too in that case?

Waterson

The post CAT sensor is only used for monitoring the condition of the CAT. The Pre CAT sensor is the primary inpt for calculating air/fuel ratio. I would imagine the combination of dipetane, cleaned MAF and ragging have cleaned out the CAT sufficiently enough to get the emissions down.

jimgoose

Waterson wrote: »

The post CAT sensor is only used for monitoring the condition of the CAT. The Pre CAT sensor is the primary inpt for calculating air/fuel ratio. I would imagine the combination of dipetane, cleaned MAF and ragging have cleaned out the CAT sufficiently enough to get the emissions down.

Some ECUs will stay off Lambda altogether when there's a problem with the downstream O2. It is, at any rate, possible.

shietpilot

jimgoose wrote: »

Some ECUs will stay off Lambda altogether when there's a problem with the downstream O2. It is, at any rate, possible.

I thought that too but my Yaris was running in closed loop even with the rear sensor dead

THEFRIDGE

Mine failed for really high readings. 3 times over the limit.
Did you test using multimeter for an ohm value? Bit lost how to test.

I see the front sensor on mine was changed before but probably need to change rear one. Hoping that's the issue as the car is running fine.

shietpilot

THEFRIDGE wrote: »

Mine failed for really high readings. 3 times over the limit.
Did you test using multimeter for an ohm value? Bit lost how to test.

I see the front sensor on mine was changed before but probably need to change rear one. Hoping that's the issue as the car is running fine.

The rear sensor won't do much on the Yaris, at least it didn't help me. It's only used for diagnostic purposes to verify that the catalytic converter is functioning and throw up a check engine light if it isn't.

The front sensor is used for maintaining correct air-to-fuel ratio. Even if you check the sensor with a multimeter and it looks good it may still be bad because the sensors get lazy and slow over time. If they aren't able to keep up with the conditions they will show wrong readings to the ECU.

If the front sensor was changed with a cheap brand it can also cause issues. The best thing to do is to get a Denso brand sensor which is what is used from factory and it will function as it should.