22 replies to this topic

[rik]

CO and lambda fail fast idle CO (max allowed 0.3%) 2.01% first run 1.41% second run fast idle lambda (must be between 0.970 and 1.030) 0.940 first run 0.959 second run My first lambda sensor is returning a good range of values so I don't think it's that... I replaced it not so long ago. the second o2 sensor is returning about 0.8V pretty constantly, what are your's like? I think it may be the actual cat because of the problems I had earlier in the year (I think my engine was running lean because the first sensor was broken)

[qwertyvx]

I had my VXT in for MOT yesterday and with the new full system with 200 cell sports cat it passed fine. Only thing is someone mentioned my Lambda sensor might be dodgy because my car drinking petrol like its water so affecting my MPG. Do you mind me asking how you check if the sensor is broken or not - thanx (Sorry for the hijack)

Edited by qwertyvx, 01 April 2008 - 11:29 AM.

[luna_s]

heres some data of mine after a new sensor

bearing in mind i've an o2sim on bank2

you basically check using an obd reader, produces results like that

the sensors are quite sensitive, my old one was reading 0.20 constantly fooling the engine into thinking it was running lean thus
forced more petrol in

[davep24]

thinks its your lambda thats faulty, the CAT appears to be working as your lambda is reading low (meaning some of Oxygen is recombining with some of the CO). The high CO will be because of the engine running slightly rich what were the HC readings?

[rik]

HC is 61ppm first run, 19ppm second run can't be my lambda again, surely?? replaced it only a month ago with an official vauxhall one what is lambda exactly? and why is my value TOO low?

[slindborg]

Lambda 1 = 14.7:1 air fuel ratio... or Stoitch (Spelling) Lower than Lambda 1 = 14.7*Lambda = RICH higher than 1 = 14.7*Lambda = LEAN shes running rich for some reason.... I'd start with clean and or fresh spark plugs. a long shot is a slightly fubar coolant temp sensor as this might move it into cold start fuelling which is rich as funk, all the time.

[rik]

I'll clean the spark plugs but they are quite new, but I quess they could've gotten dirty with the problems I was having. Are you saying that it's definately not the cat? Could it be that I still have the fpr connected to the inlet air pipe and not open to atmosphere or on the brake vacuum pipe? Biggest thing that will annoy me is, how do I check that I've fixed it without returning for the retest?

[slindborg]

no idea what your problems were lol. But its possible the plugs have gotten fouled. On first looks , I dont think its the cat at fault, otherwise the EML would have tripped for the 2nd sensor (thats its job)

[slindborg]

**edit ** forum brain fart

Edited by slindborg, 01 April 2008 - 01:05 PM.

[EdButler]

I'll clean the spark plugs but they are quite new, but I quess they could've gotten dirty with the problems I was having.

Are you saying that it's definately not the cat?

Could it be that I still have the fpr connected to the inlet air pipe and not open to atmosphere or on the brake vacuum pipe?

Biggest thing that will annoy me is, how do I check that I've fixed it without returning for the retest?

Not trying to sound like a complete wierdo, but just the smell of the exhaust gasses when the engine is warm and idling should do the trick... If its running rich you can literally smell the unburnt fuel and sulphur.

If a car is overfuelling somewhat like Rik's, how long will it take to kill the CAT?

Usual things to check are Lambda 1, State of Tune (Has it been modded without a remap, especially Cams), Faulty EGR, Air Leak on Exhaust...

[slindborg]

ive never managed to kill a cat running rich Ive killed a few going lean as the temperature of the gas goes very high and starts wankering the cat.

[rik]

What i was trying to say was,

I had a problem a couple of months ago which was ongoing for about 2-3 weeks (engine misfiring)

It turned out to be lambda sensor 1 which was constantly returning a "rich" reading, which was incorrect. Since the ECU thought it was running rich, it would have decreased the fuel amount, so the engine was in fact running lean (and for about 2-3 weeks!, getting worse as time went on).

I think this may have messed my cat up (magna flow 300 cell), as I'm almost 100% sure that my mixture (sensor 1) is running well, as it's brand new and it fixed my misfiring problem instantly only a few weeks ago.

[rik]

I'd really like to know what the post-cat o2 sensor should be reading. I've just checked and at 3000rpm it's at 0.05V Should it be lower?

[rik]

checked again this morning (after driving 30 miles to work), and the 3000rpm voltage on sensor 2 has goen up to 0.15
I'm really wondering which way to go with this.. I'm considering buying a big beefy cat with high cpi and adding flanges so I can run a decat pipe most of the year, and just get the cat out of the cupboard for the mot
Vocky, did your's pass with the 300 cell magnaflow?
Or has anyone got a standard cat section for sale?

Could this be the problem? I don't know why the bolt is sheared, but I think it only happened on the drive this morning anyway (the old egr valve was attached to that bolt)

[luna_s]

that sheared bolt might cause a slight leak but probably not enough to cause issues. you sure you havent any air leaks close to the mixture lambda ? shame i can't help with the post cat voltages as i'm running a sim, vockys did pass with the 300 magnaflow mine passed with 23 ppm HC

[rik]

luna, what's the program you use to log the readings to csv? I have the dbilas exhaust manifold ready to fit, should I fit it with new gaskets etc..? What about this coolant temperature sensor things?

[luna_s]

i use the gendan stuff, not sure if scantool does i'd fit all new gaskets yes, just to be sure, - you may also even have a crack in the standard manifold, i checked my coolant sensor by taking a multimeter reading when cold then slowly heating it up to check (harder than it sounds...) you can check ecu/temp correlation using the monitors in the OBD software too. think its worth getting a universal lambda just to make sure it isn't that ? - worth a punt for 15 quid ? its a pain when cars fail on emissions, as modern engines are quite hard to diagnose, generally garages don't have a clue either

[rik]

where's the coolant sensor located?

[luna_s]

its in the thermostat housing -

here

[vocky]

Vocky, did your's pass with the 300 cell magnaflow?

as Luna_s so kindly replied, it's passed two mots on my vx220, the last mot being last saturday