Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: terry paget on 24 June 2015, 15:04:47
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As above. This car has 2 lambda sensors, before and after catalyst. Which do I replace?
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Well, the one before the cat is the only one that controls fuelling. The one after the cat only measures efficiency, and therefore has no bearing on emissions.
But with that said, why do you think you need to change the lambda sensor? The readings could be caused by a host of other things, a random example being a slight misfire, a blow at the downpipe join, etc etc...... :y
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Thanks for quick response, James.
The MOT emissions tester passed it on CO <0.3% and HC <200ppm but failed it on lambda at 1.31, so I presumed the fault was in the lambda sensor. I see over the last 18 months I have had a persistent EML fault of P0171 (fuel trim bank 1) and I have twice changed the first lambda sensor for old spares. Do these additional facts point to faulty first lambda sensor?
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Just because the lambda value is out, doesn't mean it's the lambda sensor that has failed. The fact is that the fuel mixture is wrong (lean, by the look of things - sue it isn't 1.031 - 1.31 is MILES out). SO, anything that can give a lean mixture is possible - induction air leak, bad MAF sensor, misfire (unlikely, as it passed CO and HC) and so on.
Need some live data from it, ideally.
But yes, it's only the front Lambda sensors that have any bearing on emissions.
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Correction - reading is 1.131. Car runs well, no misfiring, stalling. Will check for induction leak between MAF sensor and engine, and check if I have a spare MAF sensor. Would it be the same as a 2.5 MAF?
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Obviously not the same as a 2.5. But could be the same as a 2.0. I will check in the morning in my parts heap.
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Not the same as a 2.0, I've got one here. 2.2 MAF is part no. 190803, 2.0 is 359806.
I see no obvious air leaks between MAF sensor and engine.
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My previous 2.2 was a bitch to get through the m.o.t each time on the same thing....I found that a very friendly tester put himself out by giving it a long time on the test and did it several times before it eventually passed,,,he said that 2,2 sometimes need more time ticking over and retrying a few times before the reading comes down,,needless to say i took it to him after that simply because he put him self out .. :D :D
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Or ....
(http://i1.adis.ws/i/washford/616247?$pd_main$)
And rag it ;)
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Thanks EMD. Are you suggesting the catalyst is tired, and in need of reinvigorating? The catalyst is a Timken aftermarket item. I was prepared for its failure last year, but it passed. This year the CO and HC readings were fine, so I presumed the catalyst was all right. In my simple way, I suppposed that an out of spec lambda reading meant that the lambda sensor was sick. I have known them fail before. They are easier and cheaper to replace than catalysts.
Keep the advice coming chaps! I have a problem.
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Cat is working fine looking at those figures. It's a mixture control problem.
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Kevin is correct, the Cat is good, its the mixture control which is out.
Something is affecting it be it an engine hat is not getting to temperature (e.g. stat stuck open) so closed loop control is not working or something is overriding or affecting the closed loop control value.
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Thanks to all for wise advice. Is it your view that the lambda sensor is unlikely to be the culprit?
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Thanks to all for wise advice. Is it your view that the lambda sensor is unlikely to be the culprit?
The lambda sensor is doing exactly what it was designed to; reporting an issue further up.
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Thanks to all for wise advice. Is it your view that the lambda sensor is unlikely to be the culprit?
The lambda sensor is doing exactly what it was designed to; reporting an issue further up.
Thanks Nick. My problem is getting this car through its MOT. If car lambda sensor thought mixture was too lean would it not report this to the ECU, which would then correct matters? If the lambda sensor was faulty, it would report duff information to the ECU, resulting in an incorrect mixture. Then the MOT tester's kit would report faulty mixture, throw up a faulty lambda reading and fail my car.
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You could indeed have a faulty lambda sensor that the ECU has detected and, in response, gone open loop but many other things could cause it to go open loop and Lambda sensor failure is not one of the more common, IMHO.
Other possibilities:
Air leak causes the fuel trims to go out of range
Temperature sensor fault causes the ECU to believe the engine is not hot enough for reliable closed loop running
MAF sensor failure causes the fuel trims to go out of range.
Low fuel pressure or tired injector causes fuel trims to go out of range
Air leak into the exhaust causes false lambda sensor reading
Air leak into the exhaust causes the MOT tester's lambda reading to be inaccurate
Is the engine light on, and have you checked the engine ECU for fault codes?
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You could indeed have a faulty lambda sensor that the ECU has detected and, in response, gone open loop but many other things could cause it to go open loop and Lambda sensor failure is not one of the more common, IMHO.
Other possibilities:
Air leak causes the fuel trims to go out of range
Temperature sensor fault causes the ECU to believe the engine is not hot enough for reliable closed loop running
MAF sensor failure causes the fuel trims to go out of range.
Low fuel pressure or tired injector causes fuel trims to go out of range
Air leak into the exhaust causes false lambda sensor reading
Air leak into the exhaust causes the MOT tester's lambda reading to be inaccurate
Is the engine light on, and have you checked the engine ECU for fault codes?
Engine light is not on at the moment, but as stated in reply#2, P0171 fuel trim bank 1 is a persistent light on this car, and twice changing upper lambda sensor has not eliminated it In 2013 MOT lambda value was 1.023, in 2014 it was 1.025.Thanks for all your suggestions, I will cheack all I can on Saturday.
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OK. Sounds like something has taken the fuel trim out of range and caused it to go open loop. :y
Can you read live data from it or just the fault codes?
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OK. Sounds like something has taken the fuel trim out of range and caused it to go open loop. :y
Can you read live data from it or just the fault codes?
Cannot read live data, only fault codes.
Cannot detect any inlet side air leaks.
Held hand over exhaust, engine running, no sound of leak; removed hand, whoosh! No exhaust leak.
Engine temp sensor? possible. Fuel pressure low, injector dodgy? Possible again. But car runs so well, idles well. Doesn't seem to lack power.
MAF sensor faulty? Could be.
Lambda sensor fault? Could be. But I would expect a fault code. I would expect fault codes for the above too.
Would live data tell me straight away? The local Vauxhall dealer might give me a Tech2 readout as a favour if it would be straightforward and conclusive.
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The live data would need a certain degree of interpretation, so you might struggle, depending on whether the guy knows his onions. :-\
The £60 they would probably charge you might be better spent on an OBDII reader that can do live data, perhaps? Might be a good investment.
I don't suppose it's suffering the cracked exhaust manifold that's common on 2.2s? That might give enough of an air leak to upset things.
Failing that, can you borrow a known good MAF and see if that clears the P0171 code?
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The live data would need a certain degree of interpretation, so you might struggle, depending on whether the guy knows his onions. :-\
The £60 they would probably charge you might be better spent on an OBDII reader that can do live data, perhaps? Might be a good investment.
I don't suppose it's suffering the cracked exhaust manifold that's common on 2.2s? That might give enough of an air leak to upset things.
Failing that, can you borrow a known good MAF and see if that clears the P0171 code?
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The live data would need a certain degree of interpretation, so you might struggle, depending on whether the guy knows his onions. :-\
The £60 they would probably charge you might be better spent on an OBDII reader that can do live data, perhaps? Might be a good investment.
I don't suppose it's suffering the cracked exhaust manifold that's common on 2.2s? That might give enough of an air leak to upset things.
Failing that, can you borrow a known good MAF and see if that clears the P0171 code?
I don't hear crackling from exhaust manifold, unlike some other Omega fours, so don't thnk it's cracked.
My son Jonny also has a 2.2 so I could swop MAFs, trouble is he lives 30 miles away, and as code P0171 is not displaying I am not sure what good that would do me.
Is this the sort of reader you had in mind?
http://www.amazon.co.uk/Blusmart%C2%AE-OM580-Diagnostic-Compliant-European/dp/B00VV3U16I/ref=sr_1_3?ie=UTF8&qid=1435403329&sr=8-3&keywords=obd+ii+scanner
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Got a Maxscan 509 (Autel) you can use if you`re passing Terry
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Got a Maxscan 509 (Autel) you can use if you`re passing Terry
Thanks Rob. PM sent
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Thanks Rob. Would this morning be convenient?
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Thanks Rob. Would this morning be convenient?
Only just saw this. thought you were popping over last night?
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Thanks Rob. I got your message last night too late to make it, so I thought I might come today. It's late to come tonight, so if I am still stuck next weekend I will fix a time early. Thanks again for the offer.
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Thanks for all the advice. Could detect no leaks inlet or exhaust, so decided to change lambda sensor. Bought one, Halfords £41, fitted Monday, rang to arrange retest, tester closed for a week. Wednesday son Jonny rang, his 2.2 losing water, see different thread. I left him MOT failure car, collected leaky car, brought home and diagnosed failed head gasket. Yesterday family gathered here, Jonny arriving in MOT failure car, now with EML on again, P0171 fuel trim bank 1. as before. Oh dear, fault still present. I then swopped MAF sensors. Submitted car for retest today, passed easily.
I reckon the fault was the MAF sensor, though engine ran well enough. Jonny's car did not like it though, running very badly. All's well that ends well! Thanks again.
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We did say the MAF......
....fuel trim is nothing to do with the O2 sensor.
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We did say the MAF......
....fuel trim is nothing to do with the O2 sensor.
You did indeed. I suspected if it were MAF sensor there would be other symptoms, like bad running, stalling, misfiring. I was wrong. Funny thing is that putting the duff MAF sensor in the other car did cause hesitant running and stalling.
Anyway, that car has passed its MOT. Tomorrow I submit the ex-plod 3.2 for MOT. Next week would have been the other 2.2, but now it needs a new head gasket, Who needs hobbies with a fleet of Omegas to occupy my time?
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What you have to consider is that the car with the faulty MAF has been effectively correcting the mixture for the bad MAF reading over time right up until the point where the correction values hit a limit and flag a code.
Put said MAF on a car which has close to zero correction value and the mixture will be way out until the learnt values also hit the end stop and flag a code.
I see so many cars where people dive in and change the O2 sensor then delete the codes, the engine runs all be it, in some cases, lumpy, and the code disappears for a bit.....until the learn values slowly correct and the code comes back some time later!
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Thanks Marks. Last time I bought a MAF meter it was £100 plus on trade club, and Vx dealer advised me to try e-bay, which I did, eventually getting one for about £100. Now I look on e-bay and they are £22 postage paid.
http://www.ebay.co.uk/itm/Opel-Omega-Vectra-2-5-3-0-Mass-Air-Flow-Meter-0280217519-0-280-217-519-/300705399172?pt=LH_DefaultDomain_3&fits=Model%3AOmega+B&hash=item4603704184
Are these any good? I ask because I am in 2 minds whether I should scrap or repair the donor 2.2. It needs a new head gasket, head planing, all connected gaskets and studs, cam belt kit, plus the MAF sensor, £300 to £400.
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Terry, I'm not sure about the EBay one but this one http://www.eurocarparts.com/search/434720550/p/home is identical to the original and a bit cheaper. :y
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The uber cheap Chinese ones are total rubbish, best avoided.
I recall that the MAF on the 2.2 is the same as used on the 1.8 and 2.0 DBW from the Astra/Vectra of similar era.
The genuine items are Siemens VDO which can be got for around £70 from the likes of euro car parts (or car parts 4 less which is the same company)
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The uber cheap Chinese ones are total rubbish, best avoided.
I recall that the MAF on the 2.2 is the same as used on the 1.8 and 2.0 DBW from the Astra/Vectra of similar era.
The genuine items are Siemens VDO which can be got for around £70 from the likes of euro car parts (or car parts 4 less which is the same company)
£86.40 from Euro Car Parts at the moment. :y
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£71.94 on Carparts4less :y (strange as its the same company as eurofartpants)
Then use code SAVEME75 at the basket and get a further £5.40 discount bringing it down to £66.54 :y
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Thanks Mark I'll check Carparts4less before eurofartpants in future. :y