Stuck with Decat and no MOT (+extremely rich condition)

[reFRence]

So I bought the car last year (1.8T AUQ) without really understanding the implications of having a decat.

My MOT has run out and now I realise that without a friend to pass the MOT, I'm quite stuck. I've read around the forum and I see that without a visible cat it will fail immediately. Now I'm not exactly rolling in money so getting a genuine cat or branded exhaust system is not really an option. I've seen some 200 cell sports cats that are affordable, however they require welding, which I don't think comes cheap. I also think that even after having done all that, it will still fail on emissions becuase of how rich it is running.
At the moment it's just sitting in the driveway and each time I get a hint at what might be causing the rich condition I go and check, only for that not to be the problem. So far I've done; MAF, DIY Boost leak test (not sure how well I executed this), vacuum leak test (garage found ill-seated dipstick), DIY fuel injector test, checked the N80, changed the PCV piping and put the old airbox back on.

I'm thinking my options are to sell the car for extremely cheap and let someone who's better equipped to deal with the problems have it, OR get a sports cat welded, fix the rich condition and then take it to be MOT'd.

Got any advice guys?

 

[mty12345]

Sorry to hear about the issues. It's hard to say what is causing the rich condition. What is the exact fault code you have? im guessing this one?

17535/P1127/004391 - Fuel Trim; Bank 1 (Mult): System too Rich - Ross-Tech Wiki

wiki.ross-tech.com

If it's decatted then it must almost certainly be mapped, could it be a dodgy map making it too rich? Has the previous owner had it mapped for extra mods and then removed the mods before selling it? There are so many possible reasons it's hard to say.

Sounds like you've covered most of the obvious things other than the first O2 sensor (not that i'm suggesting you replace it, not without evidence of a fault)
Usually the best thing to do would be to run some data logs with VCDS. See requested fueling vs actual fueling. Requested boost vs Actual boost etc, but if you haven't got the car road legal then that's not much help in this case.
\
Might just be worth putting the car in for an MOT and seeing how it does? If it fails on lots of stuff then scrap/sell it, and if it passes on everything but the CAT, then it's probably worth spending the cash to fit one, and get a VAG specialist to find the rich condition.
In my experience a LOT of garages are fine for general maintaince, but crap at diagnosing stuff. If the computer doesn't specifically tell them the part to replace, they will just start firing the parts cannon and guessing. A VAG specialist would probably pinpoint the fault in an hour or two

 

[reFRence]

First of all thanks for your reply.

That is the code, with (intermittent) at the end.
It's possible that it was mapped by a previous owner. The owner before me informed me that it wasn't mapped but they may not have known (apparently it was decatted before they had it).

Getting an MOT anyway just to see how it does seems like a good idea. I know the car needs a new tire in the rear driver's side, the sidelights don't work and it probably needs new brakepads up front. Apart from that I think it's ok. If there are way too many problems to deal with then I'll just have to sell it for cheap.
Otherwise yeah, getting a Cat welded and a VAG specialist seems like relatively little headache in comparison.

 

[mty12345]

First of all thanks for your reply.

That is the code, with (intermittent) at the end.
It's possible that it was mapped by a previous owner. The owner before me informed me that it wasn't mapped but they may not have known (apparently it was decatted before they had it).

Getting an MOT anyway just to see how it does seems like a good idea. I know the car needs a new tire in the rear driver's side, the sidelights don't work and it probably needs new brakepads up front. Apart from that I think it's ok. If there are way too many problems to deal with then I'll just have to sell it for cheap.
Otherwise yeah, getting a Cat welded and a VAG specialist seems like relatively little headache in comparison.

No worries bro, good luck with the MOT. Their exhaust gas analyser should give you an idea of how rich your mixture is too. I think the test is at idle and at 2500 rpm, both of which are when the car is at zero boost. If your rich condition is down to a boost leak, then you may find that once you have a cat fitted that it won't be too rich at those 2 points anyway. The richest mixtures should always be under hard acceleration, idle and a constant engine speed are usually a lot leaner.
If you do decide to go down the sports cat route then make sure the car is as warmed up as possible before it goes in for the MOT. One of those MOT while you wait places would probably be best, as they tend to put the car straight through rather than leaving it sat around for a couple of hours.

I take it you don't have VCDS, but do you have a cheap OBD2 reader? If so then even the cheapest ones will usually show some elements of live data. Looking at the fuel trims and the live data from the O2 sensors may help. The second O2 sensor (bank1, sensor2) is purely there to monitor the effectiveness of the CAT, it compares the exhaust gas to what it sees at the first sensor, and uses that to check the cat is working. Obviously without a cat this will show a fault, but it is only the first sensor (bank 1, sensor 1) that affects the mixture, so any issues with B1 S2 can be ignored.

There are quite a lot of videos on youtube showing what data from a working O2 (lambda) sensor should look like, same with fuel trims.

Not sure if you have checked your spark plugs but if not then check that they are in good condition and the gaps all look the same. I know you said you had done a DIY boost leak test, but if you haven't already done so, then visually check the intake piping from after the MAF all the way until the intake manifold. Pay particular attention to where the pipes go into and out of the intercooler, and also across the bottom of the engine where you find the flat pipe (pancake pipe it's commonly called) all those spots are possible leak points. Usually if it was down to a boost leak then you would also get a code for that, but worth checking anyway as it's something you can do yourself for free.

Hope that is of further help to you.

 

[reFRence]

No worries bro, good luck with the MOT. Their exhaust gas analyser should give you an idea of how rich your mixture is too. I think the test is at idle and at 2500 rpm, both of which are when the car is at zero boost. If your rich condition is down to a boost leak, then you may find that once you have a cat fitted that it won't be too rich at those 2 points anyway. The richest mixtures should always be under hard acceleration, idle and a constant engine speed are usually a lot leaner.
If you do decide to go down the sports cat route then make sure the car is as warmed up as possible before it goes in for the MOT. One of those MOT while you wait places would probably be best, as they tend to put the car straight through rather than leaving it sat around for a couple of hours.

I take it you don't have VCDS, but do you have a cheap OBD2 reader? If so then even the cheapest ones will usually show some elements of live data. Looking at the fuel trims and the live data from the O2 sensors may help. The second O2 sensor (bank1, sensor2) is purely there to monitor the effectiveness of the CAT, it compares the exhaust gas to what it sees at the first sensor, and uses that to check the cat is working. Obviously without a cat this will show a fault, but it is only the first sensor (bank 1, sensor 1) that affects the mixture, so any issues with B1 S2 can be ignored.

There are quite a lot of videos on youtube showing what data from a working O2 (lambda) sensor should look like, same with fuel trims.

Not sure if you have checked your spark plugs but if not then check that they are in good condition and the gaps all look the same. I know you said you had done a DIY boost leak test, but if you haven't already done so, then visually check the intake piping from after the MAF all the way until the intake manifold. Pay particular attention to where the pipes go into and out of the intercooler, and also across the bottom of the engine where you find the flat pipe (pancake pipe it's commonly called) all those spots are possible leak points. Usually if it was down to a boost leak then you would also get a code for that, but worth checking anyway as it's something you can do yourself for free.

Hope that is of further help to you.

I do have a cheap OBD2. It shows negative fuel trims exceeding -10% at idle. The fuel trims start close to 0 and then slowly get more and more negative over time. I remember checking the O2 sensor lambda values and them not showing anything abnormal outside of the rich fuel mix. I had spark plugs changed a while back.
As for the piping leading from the MAF to the intake; I checked the places you mentioned a while back, there was oil on the tubes near the pancake pipe (maybe related to the rotten PCV piping I changed) and the last pipe leading from the intercooler to the intake manifold was also oily - the jubilee clip holding the two pipes together had slid down so it seemed like that was where my boost leak could be. I cleaned the pipe and put the clip back on properly, then I reset the ECU by disconnecting the battery. However this didn't fix the problem as it stayed rich.
I also did get a code when it was scanned a while ago "Pressure drop between Turbo and Throttle valve" which is what lead me to believe it was a boost leak in the first place. Although considering what you've said about it running richest at higher boost, which makes sense to me for a boost leak - then it's unlikely to be a boost leak as I've watched the values under hard acceleration and they are quite normal (initially lean, and then it evens out). Once I stopped at some lights is when it would go really rich like -25%.

This is all information I failed to mention in the original post because initially I was just trying to formulate a plan of action. If this info gives you any other ideas however please let me know. Thanks

 

[mty12345]

Cheers for the extra info, it definitely seems like you've covered all the bases really, i can't think of much else other than what we've already said.

"Pressure drop between Turbo and Throttle valve" is very rarely a genuine fault, it can be now and again, but it tends to be generated by an error that is present in most remaps. It's set when the car is started with a coolant temp of below 5C.

 

[Nathan Quigley]

Get a cat on ebay for £130 by bm catalyst.. take it for a run get the cat hot and take it for a test! Do an oil change bud as I ran decat and this helped alot!, my mot tester passed away last year so had to get one done properly aswell.. use redex and mot emissions reducer stuff.. again really helped me! https://www.ebay.co.uk/itm/30417437...cHaGHdoRnK&var=&widget_ver=artemis&media=COPY

That's the link to the cat bud, good luck

 

[reFRence]

Get a cat on ebay for £130 by bm catalyst.. take it for a run get the cat hot and take it for a test! Do an oil change bud as I ran decat and this helped alot!, my mot tester passed away last year so had to get one done properly aswell.. use redex and mot emissions reducer stuff.. again really helped me! https://www.ebay.co.uk/itm/30417437...cHaGHdoRnK&var=&widget_ver=artemis&media=COPY

That's the link to the cat bud, good luck

Hey thanks so much
My engine code is AUQ which isn't listed as compatible but I will go with BM cats as I've seen good reviews online.
Just curious, is it something I can fit myself or will it need to be welded? I see the downpipe end is bolt-on but not the other end.
Thanks

 

[Nathan Quigley]

Mine is APP and wasn't listed, they will ask for your reg after purchase to confirm it will fit and yes a bolt on bolt off job pal, comes with a gasket aswell

 

[reFRence]

Mine is APP and wasn't listed, they will ask for your reg after purchase to confirm it will fit and yes a bolt on bolt off job pal, comes with a gasket aswell

Thank you, greatly appreciated

 

[Nathan Quigley]

Get this sorted lad?

 

[reFRence]

Get this sorted lad?

Hi sorry for the late reply, I have not yet changed the cat (though I have it sitting here) since I'm currently unable to start my car due to dead battery. It seems the brake lights are permanently on, managed to jump start it, left it running for 20 minutes. Turned it off and when I came back to it 5 minutes later it was dead again.
I will get back to the car when I have the time, busy at the moment but I will update you when I get the work done if you'd like to know.

 

[Olicox18]

Hey all, does anyone know if the exhaust in the link will work on my seat ibiza cupra 1.8t 2004, seems like a much easier way to get stage 2+ through an mot than getting a cat welded in ?