UK-POLOS.NET - THE VW Polo Forum

The o/s rear position and fog lamps are not working. Recently cleaned the lamp housing and refitted. Will check the bulbs (though they looked OK when I was checking over the assembly). The fog lamp indicator on the instrument panel is working. A bit concerned this might be gremlins.

Front brakes excessively binding. Discs and pads were changed this time last year just before the MOT. Had to remove and refit n/s front a couple of times. N/s piston didn't look too great. Now both sides binding. I'm guessing worn/sticky pistons. Probably needs a piston service kit or likely new calipers.

Exhaust carbon monoxide content after 2nd fast idle exceeds default limits [8.2.1.2 (b)]. Perhaps the most surprising since it was as clean as a whistle last year. I do recall changing the front O2 sensor. Pretty sure it was the proper spec (NGK?) The type installed is NGK LZA11-V3 / LZA11V3 / 1829 Zirconia Type Lambda Sensor. The cable was a bit longer than the old sensor. This was installed during the engine rebuild (25K miles cylinder head installed) in winter 2017/2018.

Fast idle test
CO=0.66 (max=30)
HC=82 (max=200)
Lambda=0.980 (min 0.970 max=1.030)

Second fast idle test
CO=0.35 (max=30)
HC=40 (max=200)
Lambda=0.989 (min 0.970 max 1.030)

Natural idle speed test
CO=0.02 (max=50)

Last year's results (August 2018 with new lambda sensor)

Fast idle
CO 0.00
HC 0

Natural Idle
CO 0.01

Any thoughts on the above, emissions in particular?

Edit: air filter recently replaced (Mann).
The coolant temp sensor was changed at the time of the engine rebuild for a Hella part.
There is possibly some Tesco Momentum lurking in the half tank of fuel.
The vehicle was sitting parked at the station for two hours before the test.

That sounds like an overfuelling problem, possibly a faulty lambda

Front brakes the pistons seldom seize out. A clean of the slider pins and of the carriers may resolve that. I'd change the fluid too

As for the lights, thatll need some multimeter testing to see if you have continuity or not on the wiring plugs.

Thanks. It does sound like over fueling, Is is possible the lamba has failed in 12 months?

I'd removed and re-greased the slider pins several times already.

Did an oil and filter change today. Old oil (Shell Helix which seems quite thin for a 5W40) was black as is usual. I had last changed it in early spring due to the vehicle doing mainly short runs (usually drop the old oil for fresh in spring and autumn) so its max 5-6 months old and maybe 5K miles. Also noticed a slight overfill which might not have helped with emissions. I've refilled with Magnatec 5W40 which I had at hand and fitted a Mann filter. The fuel is down to 1/3 so I'm thinking to fill with plain fuel, throw in a bottle of Cataclean and go for an Italian tune up. I might do a reset on the throttle body as well. A retest is cheaper than a new lambda sensor (though I'll get one if if fails next time).

I was reviewing the MOT emissions test document and noticed one thing. The vehicle is incorrectly listed as a 1.2l. Not sure how this could happen if the vehicle registration data is used. Could the specification of a 1.2l engined Polo vs the 1.4l have any impact at all on the emissions test?

littlepolo wrote: Wed Aug 14, 2019 8:18 am I was reviewing the MOT emissions test document and noticed one thing. The vehicle is incorrectly listed as a 1.2l. Not sure how this could happen if the vehicle registration data is used. Could the specification of a 1.2l engined Polo vs the 1.4l have any impact at all on the emissions test?

Edit. The engine is listed incorrectly from the database but the tester said it does not affect the measurement.

Previously I had run a readiness test and passed.

Just ran it again (engine warm) and it failed - 1110 0101

X EGR
X O2 sensor heating
X O2 sensor
OK Air Con

OK Secondary air injection
X Evaporative emissions
OK Catalyst heating
X Catalytic converter

Readiness isnt always particularly helpful

Id say you possibly have a faulty lambda. Whats its readings?

At idle (engine 70C) 1.000, 0.992, 0.996, etc.

At fast idle (2000rpm) 0.952, 0.988, 0.996, 0.976 (all over the place)

Lambda self adaption is at 5%

Its a tough one, it definitely sounds like overfuelling or you have an air leak somewhere before the lambda is getting measured

Thanks. Will check hoses, etc. Just surprised if it's the sensor because a new one was fitted this time last year (NGK).

A frustrating day. Could not find any issues with the hoses (not to say there aren't any) and so I've ordered a new front O2 sensor to aid diagnostics.

New front O2 sensor and plugs fitted.

The removed items shown below.
Now that I think of it, the exhaust was smelling a bit rich on startup for the past few months. At the same time, I noticed the engine was using a little bit of oil. When I had the exhaust heat shield off I found a trace of oil coming down from the oil pressure sensor. When I checked I was able to turn (tighten) the sensor a bit and I'm sure this was the source of the leak. Is there any possibility that oil could have contaminated the sensor? Otherwise I'm at a loss to explain (assuming the old one has failed) why it lasted only 12 months.

Starting up the engine on the new sensor and plugs it was hunting quite a bit at first which I guess is due to the battery being disconnected. It seemed to settle down after warming up.

At 80C coolant temp

idle 689 rpm

Lambda; 0.956, 0.972, 0.968, 0.980

fast idle 2499 rpm

Lambda; 0.976, 0.944, 0.986

I've got it booked in for a re-test on Friday.

Looks quite sooty, i'd say its over fuelling for sure

The biggest thing now is the CO content. How fuelly does it smell now?

It's definitely less smelly but there is a bit of an odour. Could it be the default fuel map?

I put some Cataclean injust under 1/2 a tank of fuel. I'm not going to have a chance to give it a good blast before the MOT. Should I top this off with fuel to dilute or will it be OK?