Please HELP! VW Polo 9n Emission light and Oil consumption problems

[kushla0]

Hi

I am new to the forum so please forgive me if i have done something I am not aware of that is prohibited on this forum.

I have a 1.2 VW Polo 03 Plate AWY engine, it has done about 56000miles on the clock. Recently my engine light has been switching on several times (for which I took it to my garage, to have it read by the diagnostics machine). The fault code it brings is the same one every single time: 16804/P0420/001056 - Catalyst System; Bank 1: Efficiency Below Threshold

The engine emission light usually pops up on a motorway journey, varying between 200miles to 1500miles being travelled since being switched off

The car has had the CAT changed and both the before and after CAT O2 lambda sensors changed, but I am still having the same problem.

I have had the car serviced at the same time as the CAT change (which was in December, 08) and since then the car has lost half the oil in the tank

Does any one know why this is occuring? please help :confused:

[Rustynuts]

Check very carefully for any exhaust leaks, specifically near the cat and O2 sensors. Then check the intake system for any air leaks, specifically after the maf sensor. It's an emissions problem, and that usually means an incorrect air mixture (pre ignition) or an incorrect exhaust gas mixture, being sensed by the o2 sensors.

Of course it could also be that the engine is burning oil and this is causing the emissions light to come on, in which case it's a major engine overhaul.

[kushla0]

Check very carefully for any exhaust leaks, specifically near the cat and O2 sensors. Then check the intake system for any air leaks, specifically after the maf sensor. It's an emissions problem, and that usually means an incorrect air mixture (pre ignition) or an incorrect exhaust gas mixture, being sensed by the o2 sensors.

Of course it could also be that the engine is burning oil and this is causing the emissions light to come on, in which case it's a major engine overhaul.

Thanks for the advice Rustynuts . Really appreciate it. Oh man, I am not liking the sound of the major engine overhaul

[bbewekim]

any update to this thread?

i am currently trying to solve a similar problem on my girlfriends polo 1.4 16v 52plate. (100bhp sport model).

Burns through a little to much oil i think. Got through 2 litres in about 4 months.

Throws up

1 Fault Found:

16804 - Catalyst System; Bank 1: Efficiency Below Threshold

P0420 - 35-00 - -

Readiness: 0000 0000

Cleaned the sensor after the cat, replaced the pre cat sensor and the temp sensor.

Drives fine and gives 40mpg + on any journey.

Very hesitant to take it to a garage as i can imagine it being the approach of try this... if that doesnt work try that... ending with a huge bill. I am able to pritty much replace most parts if needs be saving labour costs.

After i found the fault code, we did take it to a VW specialist... and they said exactly the same... they would just change the lambda and hope for the best as emission faults are buggers with these cars.

SOS... and sorry to raise an old thread.

[tristanhislam]

Hiya guys, I also have 03 plate AWY with 60k and have had P0420.

I looked for exhaust leaks, maf, etc but for me the problem was a faulty PCV valve sucking oil out of the crankcase into the air intake and engine. its cheap and takes 20mins (2 screws 1 jubilee clip). You can tell if the valve is faulty by seeing if causes the hose coming from it to collapse. good luck

[bbewekim]

any further advice on this? ive even put a spacer in the rear o2 sensor to see if that helped (usually done on large downpipe/decatted 1.8ts. still the same fault.

checked on the internet for previous MOT's and it appears the cars had the problem for at least 3 years and was just hidden when we bought it and (like i did) cleared before MOT as on an MOT a few years an advisory was that the CEL light was showing.

Car drives fine, its so irritating! May aswell get it mapped out of the car!

[TIDYDUBS]

Two things..........1 Fault Found:

16804 - Catalyst System; Bank 1: Efficiency Below Threshold

P0420

Your CATALYST is cream crackered, trucked/ buggered.................thats exactly what that fault code means. Remove completely and check. Then Replace it with a genuine one not after market or source a good one from GSF. One of the functions rear O2 sensor is it monitors catalyst ageing . They rarely give grief the rear sensors, the fronts can give faults.........

which leads me to point 2.....Check the wiring to the lambda probe should have 6 wires on that kiddy meaning its a broad band type. If not it will be standard 4 wire. Usually the wires break and should be all gold plated connections.Repair is easy at a VAG retailer.

Possibly the Engine ecu software may also need updating too.....there were some issues in the past with those front lambda probes.

[rotorgoat]

Hiya guys, I also have 03 plate AWY with 60k and have had P0420.

I looked for exhaust leaks, maf, etc but for me the problem was a faulty PCV valve sucking oil out of the crankcase into the air intake and engine. its cheap and takes 20mins (2 screws 1 jubilee clip). You can tell if the valve is faulty by seeing if causes the hose coming from it to collapse. good luck

Hi Tristanhislam

I have a vw polo mk3 2001(1.4 mpi 8v)(just bought it). It has just come up with the p0420-35-00 cat. error code on vagcom. The service notes say it has had the front exhaust system replaced...I imagine the Cat. Could you explain how to fix the faulty PCV valve? Do you know the part number? Thanks very much in advance

[TIDYDUBS]

Rarely do PCV's give any grief at all. The code is as described above....unfortunately. I deal with this fault alot where customers have driven around with a misfire for a couple of weeks!!!!! Little do they know what damage it has done.They also do use a bit of oil depending on the quality of oil.

[rotorgoat]

I managed to clear the p0420 code having replaced the pcv valve. There was a lot less oil residue in the breather pipe going into the air box. Since doing this I have had a clutch change and cam belt (think i bought a lemon) and there have been other problems.

Firstly there was a misfire generated so I changed the plugs and leads. The car is still running rough as old nails. Idle is no problem, its when you accelerate, there is bugger all power and it feels very lumpy? The p0420 code has just re-appeared? Do you think the oil that was pulled through has damaged the MAF? The fuel consumption is rubbish. When I blip the accelerator there is a loudish air sucking sound? Vacuum leak?

Nothing but trouble this car!! Any help would be much appreciated.

Cheers