1.7 catalytic converter replacement

[chrisjenkins]

My 2001 Puma Thunder 1.7 has failed its MOT on emissions - I'm told it needs a new catalytic converter, but my usual workshop, Formula One, can't source one (or won't fit one unless it comes from an approved source). Firstly, can I be confident that replacing the cat will solve the emissions problem? Secondly, can anyone recommend someone who can source and fit it for me? (St Albans, Herts area).

 

[RICHARD MANSFIELD2]

Hi. My Puma can be problematic in this as well. I did have a bespoke 400 cell cat made at a cost of £450 it only lasted for two years before the problem came back. I wish you luck.
Regards, Richard.

 

[chrisjenkins]

Blimey. Well that's not promising! Mind you, if I could keep the car on the road for another two years, that would be something...!

 

[DOH]

Hi Chris , can you post the MOT emissions on here from them? As I may be able to diagnose the problem for you .

Has the car been heavy on oil consumption and how has it been running in generally , any misfires or hesitance?

In the event that the Cat does need replacing then it involves removal of the offside drive shaft from the engine block support and suspension , as with it in place there isn't enough clearance to remove from the car due to being very close to the bulkhead.

Have you tried running some Cataclean through it available from most car parts stores?

https://www.halfords.com/motoring/e...and-oil-additives/cataclean-500ml-616247.html

 

[chrisjenkins]

Thanks, it's been running pretty well, but needed a new oil filter and air filter. They suggested Cataclean but seemed pretty sure from the figures that a new cat was needed. I think the crucial figure was the CO, 5.3% - ? But I'll give the Cataclean a go and get it tested again, it would be marvellous if it made the difference!

 

[DOH]

If it's got a reading of 5.3% , what was the o2 sensor reading, as that controls the emissions as well as the coolant temperature sensor ? For the CO to be running that rich, your plugs would surely be sooted up. Have you removed 1 of them to check?

 

[Pugmanaught]

As above.Your Puma's running rich. My old track car ran a closed loop idle control system without a cat showed 1.5% CO at idle with the Single O2 sensor switching between 0.2-0.9v...This is what your aiming for so the cat can operate.
Your cat may likely recover once you sort that.

 

[chrisjenkins]

If it's got a reading of 5.3% , what was the o2 sensor reading, as that controls the emissions as well as the coolant temperature sensor ? For the CO to be running that rich, your plugs would surely be sooted up. Have you removed 1 of them to check?

Hmmm... I don't see an O2 sensor reading on the report - or is that 'Lambda'? - 0.95-1.09 - does that make sense?

 

[chrisjenkins]

If it's got a reading of 5.3% , what was the o2 sensor reading, as that controls the emissions as well as the coolant temperature sensor ? For the CO to be running that rich, your plugs would surely be sooted up. Have you removed 1 of them to check?

By plugs, do you mean spark plugs? Could changing them help?

 

[DOH]

Hmmm... I don't see an O2 sensor reading on the report - or is that 'Lambda'? - 0.95-1.09 - does that make sense?

Yes that is the Lambda reading, however that is the range it should be between , what is your actual reading?

 

[DOH]

By plugs, do you mean spark plugs? Could changing them help?

Yes, but i have asked you to inspect them and post a photo here please. I am trying to correctly diagnose your problem for you. Your car is not with me

 

[DOH]

Yes that is the Lambda reading, however that is the range it should be between , what is your actual reading?

What's the mileage of the engine?

 

[chrisjenkins]

Yes that is the Lambda reading, however that is the range it should be between , what is your actual reading?

Oh, right, it's 0.85.

 

[chrisjenkins]

What's the mileage of the engine?

90,000

 

[chrisjenkins]

Yes, but i have asked you to inspect them and post a photo here please. I am trying to correctly diagnose your problem for you. Your car is not with me

I'll take a look when I get a chance.

 

[chrisjenkins]

As above.Your Puma's running rich. My old track car ran a closed loop idle control system without a cat showed 1.5% CO at idle with the Single O2 sensor switching between 0.2-0.9v...This is what your aiming for so the cat can operate.
Your cat may likely recover once you sort that.

So what's the likely solution to that?

 

[DOH]

The Lambda sensor in the exhaust manifold is very likely to be at fault and not the Catalytic converter. I recommend that you get it plugged in to an OBD2 scanner to confirm this for sure. That is the starting point.

It is also unlikely that the CO was as high as 5.3%. You need to be accurate with the info you are providing, instead of guessing.


I recommend you first check that the connector by the bulkhead isn't corroded & spray with electrical contact cleaner. Any poor contact there will throw the readings out.
If you have to replace it , the heat sheald bolts need removing and I recommend you by an NTKNGK or Bosch lambda sensor. (Approx cost is £80)
You will need a 22mm Lambda removal tool and 1/2" drive long bar , as they are very tight!

Put the Cataclean in last after the scan has confirmed this and after the likely Lambda replacement.

 

[chrisjenkins]

That's all useful advice, thanks. I'm not 'guessing' any figures though - that's what is on the MOT emissions report.

 

[Pugmanaught]

So what's the likely solution to that?

Ok..So As I'm a mech by trade I'd get a bit techi and test the O2 sensor output voltage. Either via a scanner/code reader that's live data capable, or by a digital multi meter back probing the sensor multiplug and picking up the sensors output voltage.Your looking for a contantly altering reading between 0.2-0.8 volts with the engine idling on.... the grey wire I believe....from a distant memory?!
If your cars running rich you'll be seeing 0.8v constantly. If when you rev up the engine ,on overrun the voltage reading should go to 0.2v(or go lean).
If the O2 sensors knackered it will be unresponsive to throttle movements, or just be hanging around 0.8v.
Other causes of rich mixture include a dodgy coolant temp sensor, maybe an air mass sensor, though the later isn't common .

 

[chrisjenkins]

Ok..So As I'm a mech by trade I'd get a bit techi and test the O2 sensor output voltage. Either via a scanner/code reader that's live data capable, or by a digital multi meter back probing the sensor multiplug and picking up the sensors output voltage.Your looking for a contantly altering reading between 0.2-0.8 volts with the engine idling on.... the grey wire I believe....from a distant memory?!
If your cars running rich you'll be seeing 0.8v constantly. If when you rev up the engine ,on overrun the voltage reading should go to 0.2v(or go lean).
If the O2 sensors knackered it will be unresponsive to throttle movements, or just be hanging around 0.8v.
Other causes of rich mixture include a dodgy coolant temp sensor, maybe an air mass sensor, though the later isn't common .

Very good, thanks for that - too techie for me, but I'll pass it on to who ever I can find to service it!