My MK3 Octavia 1.4TSi with 84K miles has failed the MOT emissions for the 4th year running. First year it passed after a good clean of the sensors, 2nd year the pre-cat sensor was changed, 3rd year the engine management settings were corrected, and thi year it's failed again.

Serviced every year, no running or power issues, use Shell e10 fuel.

I need to avoid another £400+ bill for sensor replacement.

Any ideas on what might be causing the failure? Is it the e10 fuel?

Thanks in advance.

Checked back with the garage that fitted the sensor, and it was a OEM item and only has a 12 month warranty. I can't believe that these can fail so quickly.

The sesnors are around £130 and screw in like a spark plug. How can they be £400+ ?

I've had S2 one fail on my Yeti, the post cat sensor, replaced it with an OEM one from TPS and no further issues for years now.

Is the car showing Oxygen Sensor B1 S1 or B1 S2 as a fault code ?

I hope it was an OEM one you replaced it with.

With the labour and cost of the OEM pre-cat sensor (£230), plus the diagnostics the total last time was £400 plus vat.

Hoping the failed sensor can be returned and I might get some ££ back if it's faulty.

Issue I'm facing is what caused the failure if the sensor has failed and hasn't been affected by something in the engine. I've heard these engines don't like E10 and I should use E5.

I've only ever put supermarket E10 in my 1.2 TSI Yeti. Never been an issue tbh.

Sure it even says E10 inside the petrol flap.

This is why going for OE Parts is sometimes the best thing to do; Skoda offer a 2 year warranty on all parts (and labour) so whilst it is more expensive, it might be worth it if there if something goes wrong.

As to why you keep failing on emissions; that could be a number of things (not just Lambada sensors). I might suggest running on some Super Unleaded for a couple of tanks and making sure that you give your car an italian tune-up. VAG engines DO NOT like being tickled along....drive it like it was on an autobahn....fast and furious style...you need to keep the revs up (and if you have a DSG, put it into manual mode to hold the revs up). Do a long journey (100 miles plus) and your car should be running a LOT better. Check things like air filters too (in case they are clogged up).

Thanks for the thoughts.

90% of my driving is motorway (around 15 miles each way three times a week), so it's running around 70mph and I am fairly aggressive on acceleration. It's a manual and its had all the services at intervals. I'll check the air filter just in case something is blocked.

It might be a time for an upgrade to a Mk 4.

Might be worth checking wiring to sensor/sensors. Had emission problem on my sons fabia and it was poor connection between sensor and loom. i had replaced sensor when fixing exhaust so I new it was brand new. Cleaned connector which was pretty oily/dirty and emissions were ok

Alasdair

Thanks. I'll try that 👍

Have a check for broken wires as well while your at it. If I remember correctly my sons connector was supposed to be clipped to something but was hanging loose. Its also not unknown for garages to just undo sensor without disconnecting connector and twist/put strain on the wires.

Alasdair

1 hour ago, Hn63Anthony said:

It might be a time for an upgrade to a Mk 4.

oh no - absolutely not. Bunch of ruffians over that part of the forum!

In all honesty, cars drive great, but I don't rate the design plus the MIB system is a touchscreen nightmare.

Edited 24 November, 202524 Nov by varaderoguy