AnnoyingPentium's Adventures - Once, twice, three times an MOT

[AnnoyingPentium]

1 minute ago, Split_Pin said:

I haven't read back but have you had it plugged in to see if anythings amiss?

Overfueling is surely either going to be the coolant temperature sensor or an O2 sensor. 

 

Aye, been rattling through various code readers and all I get is this P0171 code. Had both O2 sensors and the coolant temperature sensor replaced, MAP sensor was done for a known-good one. Beyond that, it got a new front section of the exhaust as it had developed a hole (it sounded rather fun, but it was less than handy). It's been parts darts for some time, I could just live with it, I guess, but it's MOT time next month and I've got the fear.

Exhaust video below...

[RoverFolkUs]

Have you had the tame mechanic smoke test the intake? 

By this point it must either be an intake leak, even something as simple as a split vacuum pipe or breather, or fuel starvation caused by a dicky lift pump

A fuel pressure and intake leak test would be my next points of order. Shouldn't take more than an hour's labour or so to do both. 

[AnnoyingPentium]

8 minutes ago, RoverFolkUs said:

Have you had the tame mechanic smoke test the intake? 

By this point it must either be an intake leak, even something as simple as a split vacuum pipe or breather, or fuel starvation caused by a dicky lift pump

A fuel pressure and intake leak test would be my next points of order. Shouldn't take more than an hour's labour or so to do both. 

Not had him sort this one out yet. Although I will say, I've definitely kept him busy now, he sees all of the work between this (besides what I do myself) and the Sandero. 

I'll get around to it when I'm not having to rely on the car daily, as it does still run (for now) which is alright with me. I've got a week off in February, which is coincidentally when I send it for an MOT, might just see how it fares, and get him to see to it from there, I reckon.

It would appear, like always, nothing is ever as straightforward as I would like.

[SiC]

What are the short and long fuel trims reading? I think they'll be quite high if it thinks the engine is running lean. I.e. it's chucking more fuel in to make it richer but it's not helping.

Does the 1.2 lump have any adaptations that can be reset?

[AnnoyingPentium]

10 minutes ago, SiC said:

What are the short and long fuel trims reading? I think they'll be quite high if it thinks the engine is running lean. I.e. it's chucking more fuel in to make it richer but it's not helping.

I'll sort those by getting readings at the weekend, I've been meaning to do it but haven't got around to it quite yet.

10 minutes ago, SiC said:

Does the 1.2 lump have any adaptations that can be reset?

In terms of what the car 'learns' about you/your driving, then yes I believe so. As it has the dynamic mapping or whatever the hell they call it, I'm sure.

[SiC]

Actually thinking about it I'm not sure if they might be really low. I always forget if the system too lean is it's trying to richen it but the O2 is reading lean, or if the fuel trims are really low and it's trying to run it too lean. 

I can't remember what you've done to this now but have you checked the N80 evap purge valve? They're really common to fail on VAG stuff and also fail intermittently. This could easily give a big vac leak if it's sticking, stuck or leaking. 

[AnnoyingPentium]

1 minute ago, SiC said:

Actually thinking about it I'm not sure if they might be really low. I always forget if the system too lean is it's trying to richen it but the O2 is reading lean, or if the fuel trims are really low and it's trying to run it too lean. 

I can't remember what you've done to this now but have you checked the N80 evap purge valve? They're really common to fail on VAG stuff and also fail intermittently. This could easily give a big vac leak if it's sticking, stuck or leaking. 

I've not checked any sort of purge valve (I hadn't even considered it to be honest). Just the PCV and brake servo hoses. I replaced the latter as it had split. Pipework is a weak point on all VAG stuff AFAIK, especially on the 1.4 16v models though.

[RoverFolkUs]

16 minutes ago, AnnoyingPentium said:

I'll sort those by getting readings at the weekend, I've been meaning to do it but haven't got around to it quite yet.

In terms of what the car 'learns' about you/your driving, then yes I believe so. As it has the dynamic mapping or whatever the hell they call it, I'm sure.

I think you sent me the fuel trims before and they looked ok 🤔

Actually looking back - short term 2.3% (you said it fluctuated between 2.3% and -2.3% or thereabouts) and long term was 7.3%

An up to date reading would be good, because I think those might have been before you replaced the o2 sensors. I remember the old pre-cat one had slightly damaged wiring 

[AnnoyingPentium]

1 minute ago, RoverFolkUs said:

An up to date reading would be good, because I think those might have been before you replaced the o2 sensors.

Possibly, I also had a very slight blow in the exhaust at that time, which quickly got worse.

1 minute ago, RoverFolkUs said:

I remember the old pre-cat one had slightly damaged wiring

Aye it had frayed, which weirdly caused the car to cut out when at or near idle rpms. Made it interesting trying to turn into a junction without PAS because the engine had cut out.

[SiC]

12 minutes ago, AnnoyingPentium said:

I've not checked any sort of purge valve (I hadn't even considered it to be honest). Just the PCV and brake servo hoses. I replaced the latter as it had split. Pipework is a weak point on all VAG stuff AFAIK, especially on the 1.4 16v models though.

Evap purge valve is often forgotten about. 

Some evening video viewing explaining a bit about it:

 

 

[RoverFolkUs]

In theory the fuel trim is measured by the ECU, it's just telling you how much it's over or under compensating. Whereas the lambda readings could be affected by an exhaust leak. 

I know what @SiC means above about the lean code being a failed attempt at richening the mixture or whether it's detecting the lean condition and constantly actually correcting it. 

That's the confusing thing that's always got me, you're getting poor economy but a lean code. So that would indeed suggest it's dumping more fuel in. Then you couldn't say it's fuel starvation. 

So yeah, bloody confusing!

[RoverFolkUs]

Sorry, I know I've asked you this multiple times now but quelle surprise, I've forgotten. 🤣

Any loss of power? Any occasions of difficulty starting? 

[AnnoyingPentium]

Just now, RoverFolkUs said:

Any loss of power?

Honestly, I'm not sure. It doesn't have that much to start with. There has been times where it's felt a tad flat higher in the revs and a restart has made it feel a bit better.

3 minutes ago, RoverFolkUs said:

Any occasions of difficulty starting? 

Nope, not unless the battery has given up like it did. Fuel pump primes alright, no untoward noises from it. It has always started fine, as far as I know.

[SiC]

Just watched this (humble mechanic is excellent) and it's worth a watch. Also yes my original thought was correct. System lean code means high fuel trims i.e. it's chucking more fuel in to compensate. 

 

[RoverFolkUs]

5 minutes ago, AnnoyingPentium said:

Honestly, I'm not sure. It doesn't have that much to start with. There has been times where it's felt a tad flat higher in the revs and a restart has made it feel a bit better.

Nope, not unless the battery has given up like it did. Fuel pump primes alright, no untoward noises from it. It has always started fine, as far as I know.

Ah right yes, I now remember that the technical info I found at the time said to measure the flow rate of the pump

However the "case study" was a P0171 code, accompanied with difficult engine starting and poor performance

Let's assume for the minute you have neither of the latter, and as above if the code is signifying extra fuel, (proved by excessive fuel consumption) then the issue likely lies elsewhere. 

The purge valve is a good shout 

[SiC]

21 minutes ago, RoverFolkUs said:

I think you sent me the fuel trims before and they looked ok 🤔

Actually looking back - short term 2.3% (you said it fluctuated between 2.3% and -2.3% or thereabouts) and long term was 7.3%

An up to date reading would be good, because I think those might have been before you replaced the o2 sensors. I remember the old pre-cat one had slightly damaged wiring 

Don't forget that this code is coming up as intermittent. So possibly the fuel trims maybe reading okay some or a lot of the time. Likewise be running okay a lot of the time.

N80 purge valve could be sticking open intermittently, which is what made me mention the valve as something to take a look at and ideally test. 

[SiC]

Given this code is invariably a vacuum leak (especially as most of the sensors have been changed!), being a simple N/A engine, there luckily isn't much of a intake system to be leaking nor need inspecting!

Check all the lines closely for splits. Also check that the brake booster is holding a vacuum - brakes still give assistance a few minutes after engine off? If all good then suspect the purge valve. 

[AnnoyingPentium]

2 minutes ago, SiC said:

Given this code is invariably a vacuum leak (especially as most of the sensors have been changed!), being a simple N/A engine, there luckily isn't much of a intake system to be leaking nor need inspecting!

Check all the lines closely for splits. Also check that the brake booster is holding a vacuum - brakes still give assistance a few minutes after engine off? If all good then suspect the purge valve. 

Will do. Brakes feel okay, decent assistance off them and the pedal is normal, not hard like it was before the hose was changed. The hose that I bought was a genuine TPS/VAG one, I'm sure.

[RoverFolkUs]

12 minutes ago, SiC said:

Don't forget that this code is coming up as intermittent. So possibly the fuel trims maybe reading okay some or a lot of the time. Likewise be running okay a lot of the time.

N80 purge valve could be sticking open intermittently, which is what made me mention the valve as something to take a look at and ideally test. 

Yes, I'm with you there, great shout

[AnnoyingPentium]

Me: *glances down*

[SiC]

System too lean again?

Now it's happened again, it's the time to read the live trims. Both pre code clear and post. 

It's a good thing it's on as the fault is currently active and diagnostics can now happen in this state. 

[AnnoyingPentium]

1 hour ago, SiC said:

System too lean again?

First time it has brought the light on though, at least since about July last year.

1 hour ago, SiC said:

Now it's happened again, it's the time to read the live trims. Both pre code clear and post. 

Will do. Working on that as we speak.

[AnnoyingPentium]

Before clearing...

After clearing...

[SiC]

Don't look ridiculous tbh.

How much is a decent (i.e. Bosch or equivalent) evap purge valve for this? I'd be almost inclined to suggest playing parts dart on it. Not least you've changed everything else 😆

Saying that, you should hear it clacking when the engine is running. Also worth taking it out and giving it a tap on white paper, on each end to see if any carbon from the canister comes out. 

[AnnoyingPentium]

12 minutes ago, SiC said:

Don't look ridiculous tbh.

Further adding to the confusion, lol.

14 minutes ago, SiC said:

How much is a decent (i.e. Bosch or equivalent) evap purge valve for this? I'd be almost inclined to suggest playing parts dart on it. Not least you've changed everything else 😆

About £33 if eBay is to be believed. I'll try my local factors as well.

This purge valve, and fuel lift pump are the only things I haven't changed.

15 minutes ago, SiC said:

Saying that, you should hear it clacking when the engine is running. Also worth taking it out and giving it a tap on white paper, on each end to see if any carbon from the canister comes out. 

I don't hear very much if I'm honest, but that's more a 'me and my craptacular hearing' issue than it is the car itself, presumably.

[SiC]

£15 ish after 20% promo code

https://www.ebay.co.uk/itm/234571529716

VAG part number matches up from what I can tell but please do double check. 

I think it's this one. £25 after code

https://www.ebay.co.uk/itm/334520005688

Their listing says your engine size and year. 

[AnnoyingPentium]

31 minutes ago, SiC said:

£15 ish after 20% promo code

https://www.ebay.co.uk/itm/234571529716

VAG part number matches up from what I can tell but please do double check. 

I think it's this one. £25 after code

https://www.ebay.co.uk/itm/334520005688

Their listing says your engine size and year. 

Thank you kindly.

[AnnoyingPentium]

Little run out and about across Ayrshire today... picture below courtesy of my co-pilot.

And, as I'm going past Irvine... a click, and a guiding light.

Light is gone again. MOT is a week today. It might pass second time with some luck. 😕

[SiC]

Not tried changing the evap valve yet?

When he comes to sell, I reckon you should upgrade to my old/ @Stanky Fabia. More power, more solid engine, better economy and he's even done the cambelt on it recently too!

[AnnoyingPentium]

9 minutes ago, SiC said:

Not tried changing the evap valve yet?

When he comes to sell, I reckon you should upgrade to my old/ @Stanky Fabia. More power, more solid engine, better economy and he's even done the cambelt on it recently too!

Haven't tried it yet, been waiting until I get paid.

I've been eyeing up that Fabia ever since you stuck it up for sale. I've also got my eye out for one with the 100hp version of that engine in an estate, as the extra space would be nice.