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[terry paget]

Petrol 2001 manual 2.2 saloon
Good on CO2 and HC but lambda reading varying from 1.16 to 1.036. The engine light comes on occasionally code 0420 emissions bank one. Omega 2.2s have 2 lambda sensors, I understand the first one does the measurement and the second is the German emission test sensor, not used in UK. My hunch is to change the first lambda sensor and submit car for retest, but I seek advice.

[aaronjb]

Someone can correct me if I'm wrong, but.. my logic would be:

If CO & HC are both right then the CAT is working and the mixture is right (HC would be high if the mixture was off, CO high if CAT failed), so if the only symptom is the lambda value at the end of the exhaust (as measured by the MOT) being wrong then that would imply an air leak into the exhaust after the O2 sensor.

FWIW, 1.16 is 17:1 which is very lean - I'd expect it to be running like a bag of spanners..

[frostbite]

I could be an air leak

Mine failed emissions on the first fast idle, then when it had heated up on the second run it passed

You should ask when there is a slot for a retest and get the exhaust as hot as you can for them to test again

I thought mot stations were allowed to take the vehicle for quick blast to heat them up on allocated road?

[Kevin Wood]

Agree with Aaron. Cat is working so there's plenty of heat in it, otherwise, it'd fail on HC or CO.

I would check the exhaust for air leaks, especially as it's a 2.2, and they suffer from both cracked intake manifolds and broken studs, and the flexy sections in the exhaust giving up.

If it all looks OK, a look at the live data to see what the fuel trims are up to would be good.

[dave-b]

My 3.0 elite failed on the same issue a few years ago, and it turned out be small perforations in the twin pipes before the rear box allowing air to be drawn in.

[terry paget]

Thanks to all for advice. I had managed to remove the first lambda sensor, always a challenge after 17 tears in place, it looks fine, so I shall replace it. I know I have one leak becasue it drips water when idling cold, I shall look and listen for more.

[frostbite]

I found my pin hole driving close to walls, could here it hiss on one side but not the other

[biggriffin]

Thanks to all for advice. I had managed to remove the first lambda sensor, always a challenge after 17 tears in place, it looks fine, so I shall replace it. I know I have one leak becasue it drips water when idling cold, I shall look and listen for more.

A lamda sensor either works or it doesn't, a visual inspection won't tell you anything,.

[terry paget]

Having repaired a small hole in central exhaust last night, I had a retest today. Same as yesterday, zero CO and 9ppm HCs, but lambda around 1.15. The mechanic from next door looked in, and observed that CO reading of zero is unusual and suggest weak running.

I am now advised to change the lambda sensor. Tell me if I am wrong; I believe the lambda sensor ahead of the catalyst is the one that matters. The sensor after the catalyst does nothing in the UK, it is there to be used in some European countries for thie MOT tests.

[Kevin Wood]

Yes, that's right. It'll be the pre-cat Lambda sensor if it is a sensor problem.

I'm not sure if they are the same on the 4 pot but you might be able to swap pre and post-cat sensors if they are, as a test. Then again, it means you've got to unscrew another sensor.

[terry paget]

changed the pre-cat lamda sensor, had MOT retest - no change. Tester suggested I change the plugs and plug stick. I doing so I discovered this yellow discoloration on 1 & 2 insulators, puzzling. I attach pic of plug stick of MOT failing car X807 alongside plug stick off Y118, Ben's 2.2. Plus all looked fine, though there was oil in no.4 plug hole. Tester thought he could detect slight misfire, blessed if I could, and i drove the car 200 miles 10 days ago.
https://www.dropbox.com/s/5e6qu9fw7t7h5du/plugs.jpg?dl=0

[Kevin Wood]

Yes, looks like it's had some oil or water contamination in the past, but, if it wasn't actually misfiring I don't think it will be an ignition problem, and if it was, HC would be sky high.

I would suggest getting some live data from it at this point. Without it, we're guessing.

[terry paget]

Yes, looks like it's had some oil or water contamination in the past, but, if it wasn't actually misfiring I don't think it will be an ignition problem, and if it was, HC would be sky high.

I would suggest getting some live data from it at this point. Without it, we're guessing.

Thanks. Sounds like good advice, so I need access to a Tech2 or something similar that can read live data.  And yet, some component has to be faulty somewhere. If not lambda sensor, or catalyst, nor leaking main exhaust, it's hard to think what else is left. MAF sensor? Temperature sensor? Cam or crank sensor? ECU?

Can anyone recommend a reasonably priced live data reading meter for an Omega?

[TheBoy]

Given the number of Omegas you look after, a Tech2 would be useful

[terry paget]

Given the number of Omegas you look after, a Tech2 would be useful

Fair comment. Car failed a retest yesterday, following change of plugs and coil stick, and unplugging the MAF sensor.I now wonder whether I have substituted a faulty lambda sensor with another faulty one.
But I thought Tech2s cost thousands of pounds, and there were now cheaper devices that did the same job. Not true?

[Kevin Wood]

As this is a 2.2, it should be possible to read live data using an OBDII reader or PC + cable setup, so shouldn't cost a lot. It's with the 2.5 / 3.0 engines where a tech 2 becomes vital.

You really need to know, at this stage:

Is it up to temperature fully and does the ECU coolant temperature sensor indicate this?
Is the lambda control going closed loop? If not, why not? (until then, the lambda sensor is out of the picture anyway)
If it's closed loop, what are the fuel trims looking like? (if there is a load of correction, either the air metering or the sensor is not telling the truth)
In addition, is the MAF  and intake air temperature reading roughly right, are the injector pulse widths sensible, etc.

You have substituted most of the parts directly responsible for mixture control, so either, as you suspect, you've swapped-in a faulty part or you have some unrelated problem that's yet to be discovered (maybe an intake air leak, incorrect coolant temperature reading or some other unrelated fault that's preventing the ECU going closed loop).

[terry paget]

Thanks Kevin. I will look on e-bay for something suitable. I now have 2 2.2s. a 2.6 and a 3.2 in the fleet, all OBD2 compatible, and 2 2.5s.

I called today at Downside Motors, my local Vauxhall dealer, who in the past has popped his Tech2 on my cars and given me helpful readouts. I explained my problem, and he promptly said 'second lambda sensor'. He got it on his computer, showed it me, gave me part no. (9202575), length 770mm and price £116.40. I mentioned I thought only the pre-cat sensor did anything so was the one to change, he said it was not so, he had done two in the last week. So I left, confused.

[Marks DTM Calib]

What a muppet (sorry) but the second Lambda only monitors the pre-cat efficiency, nothing else.

He should have looked at the basics like engine temperature, check to see if the lambda is switching and maybe also MAF....

[TheBoy]

The dealer guy is going purely on 0420 code, and even then has cocked up.  Changing that sensor won't fix your problem, or fix the 0420 code either.

Unfortunately, in the wrong hands, code readers can be a liability.


Did he printout anything useful, like trims?

[terry paget]

The dealer guy is going purely on 0420 code, and even then has cocked up.  Changing that sensor won't fix your problem, or fix the 0420 code either.

Unfortunately, in the wrong hands, code readers can be a liability.


Did he printout anything useful, like trims?

He did not plug anything in. He just told me that I should change the post cat lambda sensor, giving me a price and part number. I thought this was wrong, and forum members have confirmed this. Tonight I have been studying e-bay code readers and leads and interface devices to plug into laptop computers. As you said, with 6 Omegas I should have a Tech2 or something similar. In the last 4 weeks I have got my 2 2.5 estates through MOTs with no trouble, but they are V6s which have never given me emission trouble. The other 4 Omegas are OBD2 compliant, diagnosable with humbler devices.

[tunnie]

The dealer guy is going purely on 0420 code, and even then has cocked up.  Changing that sensor won't fix your problem, or fix the 0420 code either.

Unfortunately, in the wrong hands, code readers can be a liability.


Did he printout anything useful, like trims?

He did not plug anything in. He just told me that I should change the post cat lambda sensor, giving me a price and part number. I thought this was wrong, and forum members have confirmed this. Tonight I have been studying e-bay code readers and leads and interface devices to plug into laptop computers. As you said, with 6 Omegas I should have a Tech2 or something similar. In the last 4 weeks I have got my 2 2.5 estates through MOTs with no trouble, but they are V6s which have never given me emission trouble. The other 4 Omegas are OBD2 compliant, diagnosable with humbler devices.

Even worse! 

[Doctor Gollum]

Ooh telepathic Tech 2

No wonder they cost thousand to buy and £80-100 per hour to operate...

[Kevin Wood]

Ooh telepathic Tech 2

No wonder they cost thousand to buy and £80-100 per hour to operate...

Yeah, the telepathic module is extra.

[TheBoy]

The dealer guy is going purely on 0420 code, and even then has cocked up.  Changing that sensor won't fix your problem, or fix the 0420 code either.

Unfortunately, in the wrong hands, code readers can be a liability.


Did he printout anything useful, like trims?

He did not plug anything in. He just told me that I should change the post cat lambda sensor, giving me a price and part number. I thought this was wrong, and forum members have confirmed this. Tonight I have been studying e-bay code readers and leads and interface devices to plug into laptop computers. As you said, with 6 Omegas I should have a Tech2 or something similar. In the last 4 weeks I have got my 2 2.5 estates through MOTs with no trouble, but they are V6s which have never given me emission trouble. The other 4 Omegas are OBD2 compliant, diagnosable with humbler devices.

Tech2 will do more than just engine .

Happy to demo one any time you're passing, or if that dodgy Terbert organises another meet

[terry paget]

Thanks to all for advice.

MOT tester is baffled, advised me to visit local auto electrics expert Julian Howell. I did so, he said probably not worth buying a new lambda sensor. He is going on holiday until Wed 26 April, so no solution there. Returned to MOT (and tyres) shop to collect some tyres, and tester said his ramp had failed so could do more tests until repaired.

Meanwhile - from this forum I have learned that emission system goes into closed loop when engine is warm, as judged by coolant temperature, at which point lambda sensor 1 advises ECU of oxygen content of engine exhaust gases. ECU adjusts injector dwell to correct lambda value to 1.00. ECU input data is thus lambda sensor reading, coolant temperature, air inlet temperature, and MAF reading.

 2nd lambda sensor is only used in Germany and elsewhere to test emissions. In UK we use a probe shoved up the exhaust pipe, allowing air to be sucked into the BOSTON gas analyser, where it is analysed for carbon monoxide (CO). hydrocarbons (HC) and lambda value (presumably same sort of sensor as my lambda sensor).

Clearly, air leaks between MAF sensor and engine, and between catalyst and tailpipe, will confuse things. I have found no such leaks.

I cannot find an oil temperature sensor. Nor an inlet air temperature sensor, I presume it is within the MAF sensor.

Is all the above correct?

Should I change the MAF sensor next?

Should I buy an OBD2 laptop interface to test the above?

[terry paget]

I changed the 2nd lambda sensor, in desperation. I swopped the induction tract, including MAF sensor, wirh Ben's 2.2. I tried to get another emissions test, but tester said his Boston gas analyser had failed. He even offered to pay for me to go elsewhere, I said no hurry, current MOT expires April 30th.
Live data follows:
02 sensor 1 switching rich/lean every second
02 sensor 2 switching rich/lean every second
loop - closed
coolant temp 92 degrees
air intake temp 50 degrees
MAF 13kg/h at idle, 51kg/h at 3000rpm
Fuel trim at idle 0,1,-1
Fuel trim at 3000rpm between -3 and 0.

Conclude from that what you will. I don't believe the air temperature, but doubt it matters. Is the air temp sensor in the MAF sensor?
All that leaves is a leak in exhaust between 2nd O2 sensor and tailpipe. We looked for that before but could not find one. Perhaps the items I changed - sensor 2 and induction tract - cured the fault. Perhaps the Boston tester was faulty before, but if so why did not all his other MOT tests show similar results?

[TheBoy]

Well, for one thing, the cat is clearly buggered then

[Kevin Wood]

Well, for one thing, the cat is clearly buggered then

.. or not up to temperature. The one thing we could say from the original test results was that the cat is OK.

[TheBoy]

Well, for one thing, the cat is clearly buggered then

.. or not up to temperature. The one thing we could say from the original test results was that the cat is OK.

With the coolant temp being 92C, I'd made an assumption it was should be working, but of course, readings might have been taken after the car had been off for a while, and the cat cooled.

I think 2.2, like the DBW V6, has a starting cat and a main cat, with the sensors around the starting cat.  To the OP, if the starting cat is shagged, but main cat isn't, that's nothing to worry about.

[Kevin Wood]

Yep, I wouldn't be worried about the cat.

Given that his gas analyser has just died, it does make me wonder if it was telling porkies all along.

Of those figures, the MAF looks slightly on the high side, if anything. Having said that, I can't recall what is the norm for a 2.2 as I haven't Tech2'ed one for a long time. It's probably OK based on the very small fuel trims that have resulted. Intake air temperature is probably the result of heat soak. It probably wouldn't result in much correction anyway, and if heat soak is an issue there may well be a correction for that built into the ECU config.

Can't remember if the 2.2 has SAI? Maybe air is getting drawn in there? Worth blocking the system for the retest just in case the valve is leaky? If it's got it al all.

[Marks DTM Calib]

No SAI on 2.2.

Given the values seen for coolant, the fact the O2s are switching, MAF is plausible I would say its getting air into the exhaust or the tester was up the swanny (I fractured pipe on the analyser would result in O2 being sucked in).

Clearly the CAT etc is all good, HCs good, so the engine is actually in fine fettle yet there is excess O2 in the system

[terry paget]

Original testing station could not do me a retest because the proprietor, a sole trader, is unwell, and been absent for some time, so the department of transport has ruled that no more tests can be carried out there until further notice. Boring. So I took it somewhere else, and it failed again, on emissions. But this time lambda was fine 1.006, 0.995, but CO was O.58% and 0.36%.

So it looks like I need a new cat after all.



 

[terry paget]

Rejoice, rejoice! MOT finally passed, all emissions low and lambda 1.002. My thanks to all for advice.

 I had a spare genuine Vx cat section RobG sold me some while ago which I fitted. Genuine Vx cat sections weigh 10kilos, aftermarket ones weigh 6 kilos. Need I say more.

I suspect the second lambda sensor was also faulty, because having swopped it with the sensor off Ben's 2.2 it switched rich/lean just like the front sensor, while the suspect sensor, now on Ben's car, reads lean continuously.