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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.

[Doctor Gollum]

Wynns injector cleaner with some decent fuel would be a reasonable alternative if you're concerned about removing the fuel rail

[dave the builder]

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.

part numbers on 7 zap
https://vauxhall.7zap.com/en/car/v94/g/0/32-1/
I've never damaged a seal removing injectors myself .

I didn't use any fancy kit to clean or test either ,
just a 9v battery ,some wire (to open / close) a syringe ,some hose and neat injector cleaner and a plastic tub .
I squirted cleaner in while opening and closing
I did  see some small debris in the white plastic tub

plenty of youtube videos 
 https://www.youtube.com/results?search_query=clean+injectors+diy
some videos use carb cleaner

[addy]

Thanks for the info dave the builder. I have a injector tester, that will do the pulse for cleaning them, bought it at the time, because the price was good. Justified buying it to myself, as a you never know .

Doctor Gollum the wife has only put shell or BP good stuff in it. Even when we had unleaded and Super unleaded.

I have been told by someone who owns a 2ltr, said the 2ltrs are prone to the valve seals going. Apparently he had it on his, which gave the same problem as mine, high Co emissions.  I have not heard of this before, has anyone else?  The seals were done on when the headgasket went, on the wifes 2ltr. Is it possible for a seal/s to go bad, even if service the car regular, due to the wife doing lots of travelling in it? I really don't want to disturb the head, unless I have to. If I remember, once the intake manifold is removed. I should be able to see the tops of the valves. My thinking is that if I remove the intake manifold, then I do a clean on the Throttle body, even though it looks ok. And also see the injectors.

[Nick W]

Bad valve seals are much more likely to raise the HC readings, not the CO

[dave the builder]

Wynns injector cleaner with some decent fuel would be a reasonable alternative if you're concerned about removing the fuel rail

That is OK if you can drive the car and get through the cleaner & fuel mix in the tank ,then put fresh fuel in
BUT ...
if the car has failed MOT ,it can't be driven legally (except to/from MOT ,private land)
I like to use injector cleaner a month before MOT ,then Cataclean the week before then fresh fuel
!/4 tank for each treatment till the light comes on

Bad valve seals are much more likely to raise the HC readings, not the CO

Indeed ,that is my experience

high hydrocarbons on a petrol engine tends to be valve stem seals,worn rings etc
even an oil change can bring the HCs right down

High CO i've found tends to be petrol related

Thanks for the info dave the builder. I have a injector tester, that will do the pulse for cleaning them, bought it at the time, because the price was good. Justified buying it to myself, as a you never know .

you don't need to justify your purchase to me  I have loads of toys . TOOLS i mean TOOLS ! 

...... I really don't want to disturb the head, unless I have to.

agreed , even if the valve stem oil seals had failed so soon , or popped off , once the engine was warmed up ,the oil would have burned off in my experience ,and as said oil burning increases HC ,not CO

If I remember, once the intake manifold is removed. I should be able to see the tops of the valves. My thinking is that if I remove the intake manifold, then I do a clean on the Throttle body, even though it looks ok. And also see the injectors.

I can't guarantee cleaning the injectors will solve the issue sorry , it's just advice i'm giving based on my experience 

but ... clean injectors will give a better hotter burn 

couple of other thoughts ....

I use the same code reader a lot , but i've not worked on petrol 2 ltr engines since the vectra Bs and my Carltons

are there no LTFT and STFT readings in live data of ECU (measuring blocks tab) ?

obviously that would be advantageous ,but I can't remember if it's even an option 

Also ,you say about the EGR , blanking it noticeably would be an MOT fail .
however    before that legislation came in recently  I've blanked many EGRs 


 

[Doctor Gollum]

You can idle it through, say when testing the operation of the temp/fans functionality. And, as it failed on emissions, as long as it is insured, it can be legally driven to/from a place of work where MoT failure related items can be attended to...

... Such as an emissions test

[Raeturbo]

Could be throttle position sensor?

[addy]

Hi dave the builder. The only ones that sound something like LTFT and STFT readings are O2-Loop BLM Idle (Block Learn Map) and O2-Loop BLM Partial Load (Block Learn Map). They are in the live data, I posted links to on first page.

Raeturbo. The TBS is showing .53v, then every now and then .55 without me touching the throttle. Is this right or should it be showing 0v, if I am not using the throttle?

Thanks for everyones help and advice. It is much appreciated. I understand that all advice, might not fix the problem, but if I do one at a time, hopefully it will sort the problem.

[GastronomicKleptomaniac]

I'm desperate to find the solution to this... I've already said that the laptop and readings side of things is completely alien to me... if we identify something I can bash with a hammer that will help, then I'll be straight over

[addy]

GastronomicKleptomaniac that sounds like a good plan.

[Raeturbo]

https://youtu.be/9IUtl6J5F5s
 
   This is pretty good. ^^

[addy]

Thanks Raeturbo, just watched it.  I don't know what the TPS voltage on mine should be at idle(rest). It shows as .53v at idle and does move when throttle is moved. Would anyone have the voltages at idle and WOT, so I can compare them to mine?

If the voltage is too high, before the throttle is touched, then am I thinking right that the ECU, would be thinking the throttle is already being moved. And possibly put more fuel than is needed, but all the other sensors are possibly working correct, so the ECU is confused causing O2 sensor, to do what it wants?

[Raeturbo]

Not sure but I think most work on voltage the same as on the link. BTW, make sure the vacuum feed to the fuel pressure regulator is connected and not leaking.

[Raeturbo]

What voltage should a throttle position sensor?
Although many throttle position sensor voltages are manufacturer-specific, many are non-adjustable and the voltage is in the region of 0.5 to 1.0 volts at idle, rising to 4.0 volts (or more) with a fully opened throttle. For the full operational range, a time scale around 2 seconds is used.

[Steveh]

Hi my 2.0l 16v has always struggled to pass emissions last MOT same again until the MOT tester put the engine type into his computer then it passed X20XEV