[1.6 FSI P0420] - No EML

I don't see a link between P0420 and the EVAP/Tank Vent system.
If the EVAP/Tank Vent system, (including the N80), was faulty, a TV DTC would be triggered, and that's not happening. So the EVAP/Tank Vent system seems to be working correctly. Running TV Adaptation would confirm this, if any doubt remains. (BS, Group 070).

16804/P0420/001056 = Catalyst System; Bank 1: Efficiency Below Threshold.
This means the post cat lambda, (in the rear NOx cat), is measuring a higher level of O2, (Oxygen), than expected.
The post cat lambda should measure a lower level of O2/Voltage, (Voltage = O2), than the pre cat lambda. The difference should be approximately 0.25 Volts, I believe, (I can't find it specified).
The cause of P0420 is likely to be either a poorly performing front cat, or an air leak after the front cat, allowing air, (O2), to enter, and give an increased O2 level at the post cat lambda.
As there is no EML, I assume the drop in apparent cat efficiency is marginal, and not breaching Euro 4 levels.
Suggest running the relevant Basic Settings, to reset the sensors, and check the difference between pre, and post cat lambdas, which is what triggers P0420.

Basic Setting Group 034, Lambda Sensor Ageing, (Sensor 1)
Ignition on, engine on (idle)
Activate basic setting
Press the brake and accelerator pedal together and hold down
The engine speed is automatically increased > Field 4 = Test ON
Wait until Field 4 displays "B1-S1 OK"

Basic Setting Group 036, Lambda Control, (Sensor 2)
Ignition on: engine on (idle)
Activate basic setting
Press the brake and accelerator pedal together and hold down
The engine speed is automatically increased > Field 2 = Test ON
Wait until Field 2 displays "B1-S2 OK"

Mac.
 
Hi Mac,

I've gone through all (at least most) of the adaptations. I dread the ones related to lambda because they take ages.

I think group 37 never completed despite the test starting. My foot went numb so I left it.

In any case. Now it appears that the opening/closing of the valve is a bit more gradual. So I think it is better. But I never had a fully functioning car to know if this effect was in place or not. You can tell when it is transitioning between stratified and homogeneous that is for sure. Or maybe I am nitpicking.

Evros
 
The "FSI Kick" felt around 3,000 rpm, which I always thought was the transition from Stratified to Homogeneous, is, I think, actually the point at which the inlet flaps drop, and the full inlet is open.
From logs I've done, I see that the flaps stay raised most of the time at low to medium engine load and speed. They do not relate directly to Stratified and Homogeneous, as I had long thought.
I think they drop when engine speed, and load is high, and higher power is required.
Mac.
chart (3).png
 
Hi Mac,

The kick under the pedal I was referring to is not the FSI kick but a small hit that you feel if you rest your foot on the pedal while it is misfiring. You can actually feel it miss. Or maybe you are referring to the homogeneous/stratified changeover. The effect I am seeing must be related to the opening/closing of the evap valve. Now it is a lot better and very gradual. It can still be noticed when stuck in traffic butnot as much.

Evros
 
Evripidis said:
Hi Mac,

The kick under the pedal I was referring to is not the FSI kick but a small hit that you feel if you rest your foot on the pedal while it is misfiring. You can actually feel it miss. Or maybe you are referring to the homogeneous/stratified changeover. The effect I am seeing must be related to the opening/closing of the evap valve. Now it is a lot better and very gradual. It can still be noticed when stuck in traffic butnot as much.

Evros
Click to expand...
The EVAP/N80 valve is proportional, not just open or closed.
I guess to control the flow of saturated vapour into the inlet manifold.
(I think the label file should show Duty Cycle not %).
I'll have to log the N80 at some point, to see how much, and for how long, it's opening.
I'd assumed it was open, (but not wide), much of the time, but I don’t know.
Mac.
 
Before I done all the adaptations it was almost binary, it went 0%-3.5%-19%-34%.

Now it does it more gradualy from 0-35% in steps of 1.5-2%. Which is why it is not as noticeable.

The lambda changes accordingly which is good.
 
Another funny thing, when the evap is open, the instantaneous mpg on the DIS show a crazy high value, e.g., 150 but when closed it reads ---. When idling that is.
 
Evripidis said:
Another funny thing, when the evap is open, the instantaneous mpg on the DIS show a crazy high value, e.g., 150 but when closed it reads ---. When idling that is.
Click to expand...
That's the instantaneous fuel consumption?
Makes sense, idling fuel consumption minimal, too low to measure, and when the N80 is open it's, literally, running on fumes!
Mac.
 
OK. Replaced the purge valve with a bosch one. After adaptation, vcds shows very fine control steps and is better in general. Pickup is better without hesitation. But....

I can now confirm that the car is running rough when the valve is at 30%. On occasion it will diesel quite bad. The long term fuel trim has gone up to 9%.

There simply is no end to this.
 
The fault has finally turned into an EML.

Long term trims are increasing indicating a lean condition thus added fuel in the mix.

Can a faulty cat cause elevated trims? In closed loop I guess so.
 
Evripidis said:
The fault has finally turned into an EML.

Long term trims are increasing indicating a lean condition thus added fuel in the mix.

Can a faulty cat cause elevated trims? In closed loop I guess so.
Click to expand...
What do you see when you compare Group 033 & 037, sensor 1 voltage to sensor 2 voltage?
How it affects trim, depends on how the ECU tries to deal with the rise in emissions that the difference, (between sensors 1 & 2, which triggers the below efficiency DTC), indicates.
Mac.
 
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OK, done some logs and decided to have one last go at leaks.

1. Checked exhaust joints with soapy water
2. Checked intake with carb cleaner. Found a bump in the fuel trim around the filler tube while spraying. Blocked the dipstic and filler tubes temporarily.
3. Found a crack on the oil separator, put back an old one I had with new o-rings (6 euros a pop).
4. Took out the evap canister because I remembered that the car cad been running without an arch liner for quite some time. Found lots of crud in the mesh at the bottom. Blasted it off with air and put it back.

Disconnected the battery for a while and gave it a go. Done adaptations. Cat readiness takes forever so I left it. Long term fuel trim sits at 5.5% for long term. No p0420 yet and still a bit harsh when the evap turns on.

I am still not certain if p0420 is the effect or the cause of the elevated fuel trims. Trouble is you don't want a new cat being fouled by excessive fueling.
 
Hi @Evripidis,
Have a think about replacing the camshaft end cover cap and fuel pump o-rings?

Kind regards,

'The seal police'
Walking the thin line between attention to detail and obsessive compulsive disorder
😄
 
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Ha, nice one!

I would assume that the cam end caps would be leaking oil.

The oil pump I did replace when I put the other motor in. There were some very bad signs of mistreatment so I thought I'd put the old oil pump in. I think there was an o rign where it meets the block but the shaft seal I did replace. I also put gasket sealant around the edge.

If the trims stay as they are then it either means that the two injectors I put in are massively different than the refurbihed ones; or some other leak causing this.

Until I can find out if the catalyst can cause this.

Evros
 
Update on this one:

1. Replaced the dipstick and filler tube o-rings with the some from an o-ring kit I got. They went on tight but sure enough there was some play before.

2. I replaced the crank breather o-rings with after market ones (best I could do around here). Better than RTV'ign it everytime it is out. At least for a while.

The issue has become less noticeable when the purge valve opens but fuel trims have remained at 7.2% after a long drive.

I am thinking that the injectors that are currently in are not a good balanced set but it is running well within spec.

The P0420 is coming on now but it is a very old code so it might actually be that the cat is shot. It could be a number of reasons through the years with prolonged injector failure, headgasket and coil pack failure.

Evros
 
Hi guys, thank you for having me on board. I am here to add that I am dealing with similar issues with my octavia 1.6fsi.

P0420 permanent or intermittent, kinda rough idle but not rpm fluctuation. Power not really good (ok it was never impressive) but it's worse and noisy engine above 110 kmh like you cant have a conversation easily.

Some days ago I replaced throttle body due to some other issues along with engine mounts. The car has 280.000+ km on the clock and it looks like I will have to start replacing things starting with lamda sensors that maybe cheaper, but i would really like to point out what the issue is prior to throwing money in an endless pit.

There are also things to do on the car to have it in great condition so spending with no reason is a no no.

Having also an Audi A4 b9 1.4tsi btw (looooovely car)
 
Welcome. I hope we can help.
First, an import question:
Do you have the use of a VAG specific diagnostic tool, such as VCDS, to enable access to Measuring Blocks, and live data logging.
Also, what is your engine code?
Mac.
 
Hi Anthony,

It can be a multitude of things. This error code can be the result of other things that need fixing or the actual converter itself.

The cat itself can go bad if you have un-burnt fuel entering the exhaust tract, i.e., bad coil packs, leaking injectors or over-fueling because of some other issue, i.e., air leak after the MAF, sticky EGR or even just a bad sensor.

Even if you fire the parts canon at your car you still have to make educated guesses using VCDS.

You have to start making sure the every reading is within spec, i.e., intake temperature, air flow, coolant temp, exhaust temp, fuel trims, etc.

For me the P0420 has still not been resolved but I have a catalytic converter on the bench to replace the old one. I have had pretty much all of what I described above -through the years of course- that must have taken a toll on it.

Evros
 
Kalimera Evripidi, the problem is that I do not get any other faults logged (especially after replacing throttle body).

I put a liqui moly injector cleaner and made a 500 km trip which noise wise was not pleasant but have not checked vcds yet.for any outcome. I had some bad smell in the car as another indicator for sth going wrong.

Could it be throttle related? Since air could not be provided to the engine accordingly maybe the mixture was messed up?

I'm considering also to replace the dogbone mount which is bad and that's maybe the reason for idling vibrations.

But the performance and noise issue is there definitely. Like the engine is having very hard time to do its job.

EDIT: Vcds is available, engine code is BLF
 
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