Catalytic converter questions

gnhuk · Mar 21st, 2006, 14:44

Can someone explain to me, in words of one syllable, how a catalytic converter works and is it possible to clean one out? I work in IT and have little knowledge of chemistry.

Having had my car running rich for months/years I seem to have cured it but..... I assume that the catalytic converter might be "sooted up" (bear with me I don't really understand how a cat works) and will therefore fail to work in the designed manner. However I'm now getting a sulpurous smell after about 10 miles so does this mean that the cat is cleaning itself or it's totally f*cked and needs replacing?

I've got a spare brand new cat (got lucky on ebay) so I can just sling it in the boot and tell the mechanic to replace if necessary (it's service/MOT time next week).

kevinbis · Mar 21st, 2006, 15:23

Have you noticed that the "bad egg smell" is usually connected to brand new cars?
I would say it is cleaning itself.
Best to give it a long run to get it really hot and see what the emisions are!

Mike_Brace · Mar 21st, 2006, 15:42

Smell can be either a failing cat or else the car is running too rich. You really need your emissions checking to sort out which is at fault.

Mike

gnhuk · Mar 21st, 2006, 16:19

Two contradictory answers! I was under the impression that a cat, when it is thoroughly warmed up, might give a "bad egg smell" initially. This is not continuous but occurs when I get to the 10 mile(ish) mark in a journey. I've recently changed the coolant sensor for the ECU and the MPG has improved by about 15%. I plugged in the laptop afterwards and the O2 sensor 2 (I assume the rear one) now varies in value whereas before it never moved.

The car is going for a service & MOT on Monday and I don't expect to be able to give it a real thrash before then.

Mike_Brace · Mar 22nd, 2006, 08:59

The second lambda monitors the emissions post cat - the fact that the lambda varies now says it is correct - readies should fluctuate failry rapidly between 0 and 1 volt. If before it didn't move it was probably stuck on 1 volt reading i.e. rich hance smell from cat.

Mike

gnhuk · Mar 22nd, 2006, 09:53

Thanks Mike, I think I'm beginning to understand the process. The second sensor wasn't moving before I changed the ECU temp sender (it was reading a solid number without fluctuation) but now varies. The bit that IS confusing me is that before I changed the sender there wasn't a smell from the cat but now, post change, after I've done about 10 miles there is a brief "odour" which goes away again. Maybe the cat does that once it's warmed up to operating temp as it finally burns off the sh1*?

I'll still put the spare cat in the boot when I take it in on Monday, just in case, as I don't want to be paying full whack for a replacement. I presume the Lamda sensors are probably okay...............?

louis · Mar 22nd, 2006, 11:18

without getting too technical, a catalytic converter basically converts Carbon Monoxide into Carbon Dioxide, Nitrogen Oxide into Nitrogen and Water, and Hydrocarbons into Carbon Dioxide and Water the reason for this is that
Carbon Monoxide is poisionous, Nitrogen Oxide causes Acid rain and unburnt Hydrocarbons produce Smog i hope this has helped.

gnhuk · Mar 22nd, 2006, 13:14

Whoosh (sound of the above explanation flying over my head!)

That is far too complicated for me...........

louis · Mar 22nd, 2006, 18:39

the simpler version goes..............dirty in and clean out,

Mar 21st, 2006, 14:44	#1
gnhuk Balding............. Last Online: Jun 29th, 2018 10:35 Join Date: Dec 2003 Location: Linslade	Catalytic converter questions Can someone explain to me, in words of one syllable, how a catalytic converter works and is it possible to clean one out? I work in IT and have little knowledge of chemistry. Having had my car running rich for months/years I seem to have cured it but..... I assume that the catalytic converter might be "sooted up" (bear with me I don't really understand how a cat works) and will therefore fail to work in the designed manner. However I'm now getting a sulpurous smell after about 10 miles so does this mean that the cat is cleaning itself or it's totally f*cked and needs replacing? I've got a spare brand new cat (got lucky on ebay) so I can just sling it in the boot and tell the mechanic to replace if necessary (it's service/MOT time next week). __________________ Gavin VOC17969 2000 S40 1.8S -with various options (Now sold @135k miles) 2012 S40D3 R-Design

Mar 21st, 2006, 15:23	#2
kevinbis VOC Member Last Online: Feb 2nd, 2017 10:58 Join Date: Dec 2002 Location: Shoeburyness, Essex View Photos By: kevinbis	Have you noticed that the "bad egg smell" is usually connected to brand new cars? I would say it is cleaning itself. Best to give it a long run to get it really hot and see what the emisions are! __________________ Volvo V70 T5 CD 1997 Audi TT 2003

Mar 21st, 2006, 15:42	#3
Mike_Brace Former contributor Last Online: May 15th, 2024 09:52 Join Date: Dec 2004 Location: Rhosgoch, Anglesey	Smell can be either a failing cat or else the car is running too rich. You really need your emissions checking to sort out which is at fault. Mike __________________ A Volvo is for life not just for Christmas!

Mar 21st, 2006, 16:19	#4
gnhuk Balding............. Last Online: Jun 29th, 2018 10:35 Join Date: Dec 2003 Location: Linslade	Two contradictory answers! I was under the impression that a cat, when it is thoroughly warmed up, might give a "bad egg smell" initially. This is not continuous but occurs when I get to the 10 mile(ish) mark in a journey. I've recently changed the coolant sensor for the ECU and the MPG has improved by about 15%. I plugged in the laptop afterwards and the O2 sensor 2 (I assume the rear one) now varies in value whereas before it never moved. The car is going for a service & MOT on Monday and I don't expect to be able to give it a real thrash before then. __________________ Gavin VOC17969 2000 S40 1.8S -with various options (Now sold @135k miles) 2012 S40D3 R-Design

Mar 22nd, 2006, 08:59	#5
Mike_Brace Former contributor Last Online: May 15th, 2024 09:52 Join Date: Dec 2004 Location: Rhosgoch, Anglesey	The second lambda monitors the emissions post cat - the fact that the lambda varies now says it is correct - readies should fluctuate failry rapidly between 0 and 1 volt. If before it didn't move it was probably stuck on 1 volt reading i.e. rich hance smell from cat. Mike __________________ A Volvo is for life not just for Christmas!

Mar 22nd, 2006, 09:53	#6
gnhuk Balding............. Last Online: Jun 29th, 2018 10:35 Join Date: Dec 2003 Location: Linslade	Thanks Mike, I think I'm beginning to understand the process. The second sensor wasn't moving before I changed the ECU temp sender (it was reading a solid number without fluctuation) but now varies. The bit that IS confusing me is that before I changed the sender there wasn't a smell from the cat but now, post change, after I've done about 10 miles there is a brief "odour" which goes away again. Maybe the cat does that once it's warmed up to operating temp as it finally burns off the sh1*? I'll still put the spare cat in the boot when I take it in on Monday, just in case, as I don't want to be paying full whack for a replacement. I presume the Lamda sensors are probably okay...............? __________________ Gavin VOC17969 2000 S40 1.8S -with various options (Now sold @135k miles) 2012 S40D3 R-Design

Mar 22nd, 2006, 11:18	#7
louis New Member Last Online: Nov 1st, 2008 22:29 Join Date: Feb 2006 Location: Beds	without getting too technical, a catalytic converter basically converts Carbon Monoxide into Carbon Dioxide, Nitrogen Oxide into Nitrogen and Water, and Hydrocarbons into Carbon Dioxide and Water the reason for this is that Carbon Monoxide is poisionous, Nitrogen Oxide causes Acid rain and unburnt Hydrocarbons produce Smog i hope this has helped. __________________ there is no replacement for displacement or substitute for cubic inches !!!! Last edited by louis; Mar 22nd, 2006 at 18:36.

Mar 22nd, 2006, 13:14	#8
gnhuk Balding............. Last Online: Jun 29th, 2018 10:35 Join Date: Dec 2003 Location: Linslade	Whoosh (sound of the above explanation flying over my head!) That is far too complicated for me........... __________________ Gavin VOC17969 2000 S40 1.8S -with various options (Now sold @135k miles) 2012 S40D3 R-Design

Mar 22nd, 2006, 18:39	#9
louis New Member Last Online: Nov 1st, 2008 22:29 Join Date: Feb 2006 Location: Beds	the simpler version goes..............dirty in and clean out, __________________ there is no replacement for displacement or substitute for cubic inches !!!!

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