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[SP_3.2]

Do they tend to go. Had someone run a faults code test to the car today the emission light was on. Told me me that it must be the cats playing up as the 02 sensors where working ok. I Looking on the computer and could see that they are swiching lean/Rich ok and the 02 heaters where going on and off. Cleaed the code now.

What would you guys thing it could be. 02 sensor give a bad reading maybe?

Thanks

[Marks DTM Calib]

It could be the O2 sensors giving a bad reading....what they should have done is stick an emissions probe in the exhaust and get effectively a second opinion (from an external piece of kit).

[Kevin Wood]

The O2 sensors are before the cats (well, the ones that control the mixture are). It's normal for these to cycle between rich and lean once everything's warmed up.

The post-cat sensors, if present, are there to monitor the activity of the cat itself. Once the cats are up to temperature these shouldn't cycle. IIRC, they should read rich, because the available oxygen is used up by the cat breaking down the other components of the exhaust gas but I may be wrong.

The real test of a cat's function is an emissions test, however. If it passes an MOT emissions test there can't be much wrong with the cats.

They should last a very long time, unless they have been abused (physical or thermal shocks and misfires that go unresolved will kill them).

Kevin

[SP_3.2]

Sorry should have said that the 02,s post cat where showing rich. The car had its MOT last week at the guy told me that the emissions where right one the money.

Not sure where to look. ?

[Marks DTM Calib]

Sorry should have said that the 02,s post cat where showing rich. The car had its MOT last week at the guy told me that the emissions where right one the money.

Not sure where to look. ?

They should show rich....post cat there should be no O2 left and hence the lambda reports rich.....

You say the emissions were right on the money....is that a case of good or right on the limit?

[Kevin Wood]

I'd say that sounds normal and the emissions test at MOT would have highlighted a problem in the cats themselves, IMO.

Were the MOT emissions figures close to limits or well in? Did they pass straight away or did the tester need to rev it to wake the cats up?

So what is the problem at the moment? Emissions light on?

Could be that there is an intermittent problem that puts the emissions out enough to light the light but it then returns to normal. I think you need to gobtain the trouble codes that are stored (and whether they are stored or present). That might give us some clues.

Kevin

[SP_3.2]

Hi sorry was born in U S {on the money} was to say that it was way in the limits for the emissions and passed straight away. The light has come on and off over the past few months and i have replace  the 02 that was the last time showing a fault.

Could runing low on petrol or a change of petrol make any diff, Just becuse i alway use V=power but in the past week have use shell 95 ron as they had no v-power left . The car is also re-mapped which i think is for 97 + ron Petrol. this was do about 2 years ago and the light has only stated coming on?.


Thank for your help guy,s          

[Kevin Wood]

Ahh, yes. I remember now. I had the problem once due to the contaminated fuel in February but haven't had a light on since.

It would be good to get the codes read so we can identify exactly what the cause of the emissions light is.

My money is on an intermittent fault or air leak that affects the air:fuel mixture and sends the Lambda correction outside limits. This will light the emissions light and then after a while fault free it will get cancelled again. The tell tale will be whether both banks of the engine suffer the error or just one hence the need for the codes.

Mine certainly isn't sensitive to fuel. It came on in response to known contaminated fuel and after a reset with Tech2 has been fine since, on a variety of fuel, although I only use 95 RON unleaded. I didn't change the sensors.

Kevin

[Kevin Wood]

Just re-read your mail and you say the car was re-mapped. Do you know who did this? I thought there were currently no solutions for the 3.2 since the ECU needs to be flashed?

If it is the case that it has a non-standard map then I guess there may be a problem with the Lambda correction going outside limits if the mapping is a little off. It really needs a Tech 2 to watch the live variables to see if anything is close to limits during driving, I'd say.

Another thing you could also try is to repace with the standard ECU firmware and map and see if that clears it.

Anything else that might affect fuel delivery (fuel pump, filter, fuel pressure regulator, injectors, air leaks, MAF, air filter, etc.) should be checked. I guess you've already been there though.

Kevin

[SP_3.2]

Thank,s for the infor. I had the re-map done back on 05 by a company in Bromsgrove called Chipped uk. Car had been fine up until now.

will be getting the codes read and checked in a few week and will see what it says.

Was thinking the MAF but not sure how to check it?

Thanks for the help.      

[Marks DTM Calib]

Was thinking the MAF but not sure how to check it?

Well dont, because it wont be......no symptoms point to it.

The faults are being flagged by the lambdas that do the checking, not those involved in the mixture control.......I suspect removing them and giving them a quick clean in an ultrasonic bath with plain water in would sort it out.

[VXL V6]

Perhaps we can have a lambda 'cleaning' party...... There's a few 3.2's that need this!