Emissions Fail

[Paul Fraser]

Took the 986 for its MOT yesterday and filled up with 97 RON fuel rather than the usual 95 RON just before (long story) so that it went into the test with probably a 60:40 mix of 97:95

Would this (dumb) fuelling error have contributed to the following awful emissions numbers? No current CEL lights and the car seems to drive fine at the moment.

2500-3000 RPM

CO 5.09% actual 0.30% Max

HC 413ppm actual 200 Max

Lambda 0.91 actual 0.97-1.03 Allowed

These numbers seem to say to me that the fuel/air mix is too rich. If it is not the fuelling mistake any suggestions as to where to start (I would have said cats but the low Lambda number doesn't seem to be consistent with that; if it were those I would expect the Lambda figure to be too high).

TIA.

[logray]

Hello!

Do you have a Durametric/PST2/PIWIS or other reader?

What are your O2 sensor readings?

What are your FRA/TRA readings?

MAF readings (voltage and air flow)?

Edited August 23, 2011 by logray

[Paul Fraser]

Hi, got out the Durametric and got the following fault codes:

P0154 O2 sensor ahead of cat

P1115 Resist limit O2S ahead of cat B1

P1119 Resist limit O2S ahead of cat B2

P0134 O2 sensor ahead of cat bank 2?

Cleared them and rebooted the software a couple of times but only P0130 O2 ahead of cat conv bank 1 appeared after that.

Other readings:

O2 sensor voltage 0.14V steady and 0.08-0.67V fluctuating

FRA 1.28/0.94

TRA 0.08/-0.06

MAF 1.35V 14.5 kg/h @ idle; 1.92V 44kg/h @ 2500RPM

The readings seem to point to the right hand O2 sensor being dodgy, but the reoccurring code seems to point to the left hand one...

Over to you, and TIA.

[Loren]

P0130 Oxygen Sensor Ahead of TWC, Bank 1 – Signal Implausible

- Short circuit to battery positive voltage

- Faulty sensor with limited voltage increase

- Short circuit in signal wire to sensor ground (intercore short circuit)

[Paul Fraser]

Thanks again Loren. I think I may just replace both as I can't understand the fluctuating #2 figures, unless of course that is normal and a steady reading isn't!!

[Loren]

Check the wiring and connector - if all is good replace the O2 sensor.

[logray]

Fluctuating o2 sensor is good, but voltage should read higher indicating you might have a tired o2 sensor, it might still be OK.

On the other sensor...

If the voltage is steady that is not good (assuming the engine is hot).

[Paul Fraser]

Yes, engine was up to temp. I replaced the sensors about 3-4 years ago with a couple of cheap and cheerful ones. This time I'm going to get a couple of Bosch ones.

Thanks to you both for your help. And also Durametric for their code reader -- it proved useful a couple of years ago when I had a couple of ABS sensors pack up.

Suspect that I'll have to replace the cats as well: they are 14 years old now and all that HC contamination will not have done them any good...

[logray]

You might check Amazon UK for the Bosch sensors... I bought 4 new ones from them on the USA site for around $225 total IIRC.

[Paul Fraser]

Best I could find was £125 for two at Eurocarparts who have 25% off at the moment. They are ~£85 ($130ish) each elsewhere.