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[addy]

Well took the wifes 1995 2.0ltr 16v Omega, for its yearly MOT. And again it failed on the CO on fast idle test. And just scraped through on idle test.

It went through last year, just scraping through on the fast idle, but idle test was really low. I changed the exhaust from down pipe to back box, including a type approved cat. I changed ECT sensor, genuine NGK Titania O2 sensor, that was checked directly with NGK, to make sure I had the correct one,thermostat and other parts, as suggested on here the year before.

Here is the link to the conversation. https://www.omegaowners.com/forum/index.php?topic=145812.msg1921223#msg1921223.

The CO is well out of range, this year. As can be seen by the fail sheet. I took the car, the long way round to the MOT place. And it was hot, when I got to the place. Fan also cut in just as he was about to test emissions. As you can see he tried the test twice, with no luck.



 I did some live data, a few minutes after I got home. So car wasn't cold, fan did cut in as I was recording the data.  Can anyone point me, to what could be causing this problem?

https://drive.google.com/file/d/1BEAYkCx-ps0gppKL93MeB02rre7HWO3c/view?usp=sharing.

The one thing I did notice, but it seems to have always done it, is that it goes from closed to open loop, as the O2 sensor voltage changes. I don't know if it is, the thing that cannot be mentioned to I used to get the live data? But the voltage fluctuates up and down quite quickly.  There is also a smell of petrol from the exhaust, when on tick over.

Thanks in advance for all help.

[Enceladus]

Which thermostat is currently fitted? Is it still the Circoli one or did you replace it?
And what cooling fan switches did you end up with?
I ask because your engine still seems to be running cool.

The engine still seems to be running rich and there is a petrol smell from the exhaust at idle.
The thermostat should remain closed until it starts to open at 92°C. It should be fully open at 107°C. If the thermostat opens too soon or is stuck open then the engine will run cool and run rich(er).

What about the MAF sensor, was that changed?
Also what make and model was the "type approved" catalytic downpipe?

As suggested by Doc Gollum in last years thread. Did you disable the radiator fans and check if the engine now gets up to operating temperature? Does that have any effect on the open/closed loop issue?

[addy]

Changed thermostat for a Gates, all sensors recomended to change i did. Cannt remember radiator sensors make sorry. It passed last year.

Done some live data today from car being just started, to fan coming on then off. Did a vacuum gauge test, that stayed in the green at 19. Checked spark plugs and wells. No oil and plugs seem ok. Managed to record a osciliscope of the O2 sensor at idle to a bit of revs and one at 2500revs. Also recorded the sensor going from closed to open as the voltage changes, also the Block learn readings.

all plugs looked like this
https://drive.google.com/file/d/1fZpU0nQUTvLNTQHz9e_gH29KJQyMuIcn/view?usp=sharing

Live data from cold to fan cut in.
https://drive.google.com/file/d/1G4xvnpnHwXiHtOBdUx0Pk4ShUIZixhRx/view?usp=sharing

O2 close and open loop with blocks
https://drive.google.com/file/d/1sjks-Fs4lTb49AJmVv0GJpslQ14pbmj5/view?usp=sharing

Video osciliscope of O2 at idle then a bit of revs
https://drive.google.com/file/d/18tAtShsEOh2JraSOAlzGTG-9romoe0fq/view?usp=sharing

Video osciliscope of o2 at 2500revs
https://drive.google.com/file/d/1OKb1OtPi9K1x10I_yA1CXl8KKXhNp_Sl/view?usp=sharing


Thanks for all the help. Much apreciated.

[addy]

Hi Enceladus

Sorry for delay, been busy with hospital appointments.  The cat that I fitted EEC VX8020T type approved cat. I did the fan disconnect test, it made no difference. It was still going close to open. Would it be because the O2 sensor is Titania, so the data from the "My Naff Code Reader", shows as going open to closed as voltage changes, with car being a 1995?

I have got a new genuine NGK O2 sensor coming. As I read on here someone with the same as mine, had a leaking new sensor. Also going to fit another new ECT sensor, as you said one on car is still showing as cooler than it should. In another topic on here from someone having the same problem. A member iansoutham, said he always had emission problems.In the end he put a 2.2 cat on with a blanking plug where the second lambda goes and he ended up with 0.03% co.

Do you think this is something worth looking at, as I have found a  BM 2.2 type approved one. It was mentioned pattern cats are rubbish. I do have a old registration, for a 2.2 I had as a Registration No is usually asked for, before they sell the cat.

Thanks for your help. Much appreciated.

[iansoutham]

Have replied to you PM.

I find that the single cat on the 2.0 never gets hot enough to work properly under MOT conditions due to how far away it is from everything. I ran it once on a 25 minute “cat warmup mode” on the emissions machine and it dropped like a stone after approximately 22 minutes at 4500rpm with the exhaust tailpipe emissions so hot it would scald you as you tried to remove the probe. I heat-wrapped mine which made it better but still went to the 2.2 one in the end.

[addy]

Hi iansoutham

Thank you for replying to my PM. It is very helpfull and interesting.  Have been looking and think I have found a couple of Type approved 2.2 cats?

https://www.ebay.co.uk/itm/163304697866

I know Klarius used to be quite good.
https://www.ebay.co.uk/itm/165076847393

Thanks again
Addy

[Doctor Gollum]

You don't need a Type Approved cat for your 2.0

Should open up a few options...

[iansoutham]

You don't need a Type Approved cat for your 2.0

Should open up a few options...

You are absolutely correct, in fact I do not believe that they make a type-approved cat in that exhaust design (although I have seen many that claim to be) but I will say that based on my other cars I have found that bin-approved cats generally only seem to last a year at best.

[dave the builder]

It's over-fueling because it's going open loop again though 
you could stick a big fat sport CAT into it with an electrical metal snotter glue gun (mig welder)
but the question remains why ....after going closed loop does it go open loop 
leaky injector perhaps    you replaced the CTS (though it's not uncommon for an old loom to break down , but the CTS seems within parameters on live data .
if the wet stat failed open or fans kick in too soon due to faulty temp sensors on the rad then the CTS would show a lower temp .
It's a mystery ,I have been reading this and the previous related thread .

[addy]

Hi dave the builder

From recommendations in the old post. I changed the ECT. MAF, Idle Air control valve. A new correct for engine Genuine NGK O2, exhaust from cat back, with a Type approved cat (well it was purchased as a type approved, as checked before I bought it). Fitted a Gates thermostat, that was linked by Doctor Gollum to me in the old post. In the old post I did the other suggestions aswel.

l I have another new O2 sensor coming, as someone in another post, with the same sort of problem on a 2ltr. Were saying they had a O2 that was leaking, letting in air. Just incase the one on the car now has the same problem?

I have done a vacuum test which shows ok. Checked plug wells for oil, nothing. From what I can see, no richness or oil showing on spark plugs. There is no smoke from the exhaust, just smell of petrol. I have a new Throttle body sensor, to replace the one on the body, not done yet. I have looked inside the Throttle body, both sides of the butterfly to see if there is a build up of oil. It looks clean.

I have not touched the EGR Valve, but was thinking of removing it and blanking it, just incase it has failed. Also looking at getting a new manifold, without the fittings and holes, for the air system and EGR,

I have bought a O2 reader tester, that does Titania that allows you to force a rich or lean test. I was going to back probe the O2, then see if the live data, changes as I force a rich or lean. Does this sound like something worth doing?

As I said before, I am not sure if it is "My Naff Code Reader" getting confused, with it being a 1995 model and a Titania O2 sensor. So as the voltage goes from high to low, it shows it as closed then open?  Unfortunately I don't know anyone who has "My Naff Code Reader" and possibly a 1995 2lt, to see if they have the same thing going closed to open.
 
Thanks to everyone, for your patience and for all you help and suggestions. Much appreciated.

[Raeturbo]

Have you changed timing belt recently? Just saying as could be a tooth out?

[addy]

Not recently. I had a mechanic, who has done them loads of times, do the last one. It will be due another change soon. But I could remove the covers, now just to check everything is still spot on.

Never had emission problems until recently. I even had a old 2.5, that when it went for a new belt and water pump, that it was a tooth out, it never failed emissions test. Are the 2ltr 16v more picky on not being a tooth out?

[Raeturbo]

Not sure, but if it is out it could certainly be due to that of course.

[dave the builder]

As you have fired the parts cannon at most things  ....
rather than aiming at the same target again,(another new cat ,lambda etc ) maybe consider a new target .
I had similar problems with an Astra years ago ,code reader data was all ok, new cat and much money spent on parts etc etc 
in the end I put another astra next to it and transferred/tried parts i'd not replaced .
the injector was the issue (single point injection x16szr engine)
it passed the MOT with virtually zero emissions afterwards
obviously the Omega 16v has 4 injectors ,so harder to do 

plenty of youtube videos on how to bench test and clean injectors though  without much expense 

NOT saying it IS the problem ,but maybe worth considering 

[addy]

Hi dave the builder

I have been thinking, that maybe they could be dirty. Have been looking at the kits, that fit onto the fuel rail and use pressure. But unfortunately don't have or know anyone with a compressor. I was thinking of taking the intake manifold off, as I cannot find the parts code for the O rings, so don't want to disturb the injectors and damage the seals.