Admitting Defeat....Petrol Emissions Woes

[darrenjlobb]

Right guys..

Im totally out of my depth here, I have no clue when it comes to petrol emissions...and this is driving me insane!

One of my daily drives is a 1.6 ph2 306, 1998. so 1.6 8v TU motor...

Story is, last year (before my ownership) it struggled to pass MOT due to "Emission test struggle to pass CO level high" But it did pass obviously and got MOT. However it did have a new CAT and new (third party non genuine) lambda sensor sensor fitted...

Anyway, 2 weeks ago i fitted a new CAT (not genuine, one of the generic 80 quid ebay jobs) thinking that i could just bolt it to the car each MOT to let it pass)...but it seems that wasnt the cause, as its just failed the MOT on the same thing.. "Exhaust emmisions carbon monoxide content after 2nd fast idle excessive"

Question is...what can I do to make it pass / what is wrong... Here is the results...:



Only thing I can think of is swapping the generic lambda sensor for a brand new genuine bosch one....however when reading in pp2000, the mv output on the oxygen sensor goes up and down from 180-750mv..cycles every 1 second or so, pretty quickly...which im led to believe is normal as the ecu pulls / ups the fueling to maintain the correct mixture..so that would make me think its working ok ? Unless its reading wrong / holding the engine at the wrong mixture?

Open to any ideas as just need to MOT it, clean MOT other than this..the one thing i cant test, and really dont care for...

PETROL POAD!!!!

xx

[darrenjlobb]

Worth noting the genuine lambda is 80 quid...so kind of bit risky / waste of money if its not that...which i am doubtfull about...engine is high milage (155k) if that makes any odds...but it drives spot on..and goes "well" imo for what it is.....

[Niall]

Know anyone with a genuine cat you can borrow? Generic ones really are shit and even with a really healthy engine, will only just pass.
Put a tank of good petrol in it, bottle of Forte or similar then rag it to death and get it roasting hot just before the MOT. Might get the emissions down just enough to pass.
Although having a cheap lambda won't help, the various TU ECUs do just use a bog standard reading (unlike the XU GTI ECU which is why generic lambdas for these don't do anything good) so that should be ok.

[Connor]

Could be a duff cat, we had a mondeo in this week and last that has gone through 3 cats... 2 bargin bucket ecp crap and finally a bosal one, which has now sorted it

[Rippthrough]

There's some really shit generic cats about that shouldn't even be allowed to be sold. Usually with a sticker on saying made in Birmingham...

[Niall]

There's some really shit generic cats about that shouldn't even be allowed to be sold. Usually with a sticker on saying made in Birmingham...

This TBH. Genuine cats are expensive not because of main dealer mark up (although I'm sure that does fall into it slightly) but because there is a lot more precious metals in them that filter out all this crap. The cheap ones are just shite especially seeing as the likes of ECP just throw them around their vans and warehouses and don't treat them well at all so chances are, they just don't work by the time they get to you.

[Toms306]

The Lambda reading is also out on the 1st fast idle test though, surely the cat can't affect that reading?

Although I realise that could just be a low engine temp as it dropped for the 2nd one....and 'warm coolant pipes' doesn't seem overly scientific lol.

[Niall]

The Lambda reading is also out on the 1st fast idle test though, surely the cat can't affect that reading?

Although I realise that could just be a low engine temp as it dropped for the 2nd one....and 'warm coolant pipes' doesn't seem overly scientific lol.

Yeah Lambdas don't work well at all until heated up hence why they have built in heaters but again, cheap ones just don't work that well. Its passed on the 2nd idle but not very well. This is why i always give my car a good ragging before its mot. Last years they left it to heat up for 15 minutes as i literally drove it 1 mile to the test station from cold. 2nd test passed perfectly.

[John1.4]

almost guaranteed the crap values on the 1st test were low engine temp / cat not warmed up, i always request they do the emissions first as the cats do cool down quite quickly once the engine is shut off, rag the engine to death just before etc...

when's the last time it had an air filter/plugs?

[Paul_13]

What about the engine temp sensor?

[THE_Liam]

Right, I will be flamed for this, but when I had this issue with my 106 GTI I poured a bit of brake fluid in the tank and took it for a 100 mile rag then straight for the MOT, it passed easily...

About 250ml, and yes I'm aware this could cause all kinds of problems but if it's a 155k TU5...

[welshpug]

What about the engine temp sensor?

this, seeing as you have PP2000, have a look at the temp its giving, there's also a resistance range they should give.

[darrenjlobb]

Engine is fully serviced except plugs, everything else is new...surely spark plugs cant effect the emissions unless there literally falling apart and not sparking lol...

So even tho its a brand new "cheap" cat its possible that thats the root cause? just scared to go and buy a genuine one if it makes no odds...Ive seen people who have managed to ALMOST pass with NO cat fitted..so thought on a stock engine any new cat would allow it to pass...

In pp2000 there are two "water temp readings" both read within 1 degree of each other?

It did almost pass at one point, but not quite, would some fuel treatment stuff really make a difference? Being a diesel man i see right past these things normally...

[Connor]

If it nearly passed, then id take the car for a good raggin and try it again, worth a go

[Niall]

Providing the temp sensor is getting above 60 when the car is warm, it will be fine. On these old TUs, its purely used to switch the ECU off of its cold start map where it is very rich.
New plugs would make a difference. If they are wearing out, they can create a weaker spark which does make a difference.
How friendly is your tester? If it only failed on emissions, go out and rag the tits off of it, get it really hot (i know you guys don't know what a motorway is down there but id take it up a motorway in 4th gear to get it really hot) and then drive it in and get it on his machine. If it still fails, see if you can find anyone with a genuine cat you can borrow.
Edit: These fuel additives can make a difference. Ive always found Forte to be good. Expensive but you notice a big difference in the running of the car.

[darrenjlobb]

Oh dont worry, it got driven on the limiter the whole way there, half way home again, and then back.... was parked up mind for id say 5-10 mins before he tested it
however from the start of the test he left the engine running...

[welshpug]

I dunno where it would get the two water temp readings, there's only one sender for the ecu

it is worth checking the plugs as they are a consumable item, they do wear out eventually and a set of NGK's would be £6 or so at the most.



cheap cats are notorious for causing issues like these btw, often need to get them roasting to get a pass and often they barely do and never last more than a year, you really dont want to be buying a genuine item btw, worth more than the car, though if you can find one that hasn't been weighed in yet then an used o.e unit should be good.

[Niall]

Or if you have any gti6 parts lying about, like a genuine gti cat, weld that in if it will fit in the exhaust tunnel. Providing it works, it will pass with that on!

[darrenjlobb]

Right well ill throw a set of plugs in it, given how easy that is / cheap...but like you said, I dont want to be buying a cat....there hundreds of these motors around so surely the damn thing should pass with it on there :S I do have the old cat which was on it for last years MOT where it "just" passed..but im pretty sure thats a cheap aftermarket one two..thats more of a round tube shaped cat, where as new one is more like a hdi style shape....

it said water temp L / water temp R i think or something? either way they wre a similer reading to the dash, so id have thoguht correct...

[mikey b]

Yes spark plugs will help a bit I've had loads of 106s come in and fail and we have done every thing you have and then change the plugs and it made it pass but one thing I would say it you have to rag the shit out of them get the cat glowing almost red lol and then they pass do you have access to any plug in tools to read the live data on the lambda sensor

[simonh]

If you weld in the two cheap cats one after the other you'll have a pretty decent chance of a pass. The closer you can get them to the engine the better so they heat up faster. Combine it with a decent fuel treatment and new plugs and it should be almost guaranteed!

[Eeyore]

If you weld in the two cheap cats one after the other you'll have a pretty decent chance of a pass. The closer you can get them to the engine the better so they heat up faster. Combine it with a decent fuel treatment and new plugs and it should be almost guaranteed!

Two cats are the way forwards.

[daniel909]

Had a look for a cat darren but the one I have is after market look pretty f*cked sorry

[Dean]

Leave a case of beers in the seat and hope the MOT tester plays ball.

[shazilla]

i got a genuine one for sale. PM me!

[JJtheHITMAN]

The cheaper 12 month warrenty cats are only designed to last 12 months. Disposable cats. The contents of em are waaayyyy inferior to the genuine or OE counterparts. I usualy sit em on 3k for 5mins before i test em and as its setting up if it struggles to go through 1st time. Got any leaks on your exhaust? How many boxes?

[kentiiboii]

Try speaking to the tester tell him you've changed it all including cat.
I've done it few times and they lowered the revs to get it through

[C2K]

Shit cat for sure is the cause. Pattern cats are just wank full stop.

[gretsch-drummer]

My 1 year old, £40 CAT failed emissions this weekend. (lucky my MOT tester sorted it out for me *winkwink nudgenudge*)

So yeah, cheap CATs are cheap sh*t.

[darrenjlobb]

It was like 80 quid and fitted the day before.. Bledy petrols