Catatonic converters

[GlynMo]

Hi,

I'm looking to the knowledgeable Griff fraternity to help me with a problem. My Griff has just failed its French MoT as the emissions are too high. It's a '98 500 and has only done 20,000 miles so it seems strange that the cat con should need replacing. Any ideas as to other possible faults before I look for a replacement?

Thanks.

[blitzracing]

Catalysts only fail if there is another problem such as too much fuel going into the engine, or the fuel is contaminated. Physically catalysts can melt (too much fuel) or if they are heavily knocked or shocked with cold water they can fracture, both are easy to see if you can remove the catalyst and look down the tube you should see a fine matrix inside. Any holes or molten metal means its knackered. Any silicones that has got into the engine or fuel will also coat the catalysts and stop it working. In terms of too much fuel from the engine, a faulty AFM or lambda probes are a good place to start- but you really need some engine diagnostics to check for fault codes from the ECU. Genuine catalysts failure is quite rare so dont assume just because the emissions are bad that this is the cause.

[GlynMo]

OK, thanks. I have an ECUmate so I'll use it in anger for the first time over the next couple of days. No doubt I'll be back!

[LordGrover]

Catalytic?

[Pixelpeep7r]

damn autocorrect?

[GlynMo]

LordGrover said:

Catalytic?

You call them what you want, I'll stick with catatonic!

[bluezeeland]

There you were, Glyn, worrying over your headlights.........its in another department

You need an Rovergauge interface for the ECU (14CUX ?) for instance from Mark (blitzracing) to diagnose were the problem lies (multitude of possibilities)

I've got one, but its a bit of a drive !

please report outcome

Frank

[Toma500]

Seeing as your in France . The mot bods might know they may not not be getting the cat hot enough they need to be hot to work properly ask them to test it again after a short runabout .

[GlynMo]

I drove the car there and the technician tested it straight away, so I can't use that excuse unfortunately.

[Toma500]

Ahh never mind just a thought .

[GlynMo]

bluezeeland said:

There you were, Glyn, worrying over your headlights.........its in another department

You need an Rovergauge interface for the ECU (14CUX ?) for instance from Mark (blitzracing) to diagnose were the problem lies (multitude of possibilities)

I've got one, but its a bit of a drive !

please report outcome

Frank

Yes Frank, I think I'd have preferred the headlight problem!

[bluezeeland]

GlynMo said:

bluezeeland said:

There you were, Glyn, worrying over your headlights.........its in another department

You need an Rovergauge interface for the ECU (14CUX ?) for instance from Mark (blitzracing) to diagnose were the problem lies (multitude of possibilities)

I've got one, but its a bit of a drive !

please report outcome

Frank

Yes Frank, I think I'd have preferred the headlight problem!

Yes, can imagine that (just to rub it in, mine sailed thru MOT/emissions test last week )

[Sardonicus]

Post up the emission results

[GlynMo]

Sardonicus said:

Post up the emission results

CO: 2.01%
Acc: (whatever that is) 1.51%
Lambda: 0.95

Google reveals that:
CO should be < 0.3% at idle, < 0.2% at 2500rpm
Acc should be ?? (unless Acc is the 2500rpm reading)
Lambda should be between .97% and 1.03%

Does that provide any insight??

[Sardonicus]

I can tell you straight out that is not down to a non functioning cat you have something else going on there faulty O2 sensor, coolant sensor, air mass etc, pre-cat emissions (not referring to a pre-cat TVR by the way) are generally around 0.40/0.50 the cat just rings that last bit down to say 0.15/20 for example your CO is just to high period a healthy cat will never pull that CO down that much my advice is not TVR specific but that dont matter, like Blitz said you need to do some diagnostics

[GlynMo]

OK, will start tomorrow.

[Peter66]

You should also check the ignition timing. Although I have a precat mine also failed the emission tests and we could not get it right, because as we later found out the dizzy was moved.

Peter

[GlynMo]

These are images off the ECUmate.

First screen


Engine start


No faults


Tickover


Throttle


Lambda readings at tickover


Same a minute or so later


Stepper motor


Idle control


I also have short videos of the lambda readings at 2750rpm showing the fluctuations and the AFM screen at idle but I don't think I can up-load them. If anyone thinks they can help with translating what all of this means, I can email them.

Thanks for looking.

[blitzracing]

have another look at the lambda trims- I think on the ECUmate it shows a range of plus or minus 128 out of the total range of 256, so the trim values should shift around the central value of zero, but be constantly shifting between the positve and negative values. If you only see a changing positive or negative value then there is a problem with the fuel control or a sensor input error. If the trim does not cycle around a mid point of 0 the catalysts wont work as it should.

[GlynMo]

blitzracing said:

have another look at the lambda trims- I think on the ECUmate it shows a range of plus or minus 128 out of the total range of 256, so the trim values should shift around the central value of zero, but be constantly shifting between the positve and negative values. If you only see a changing positive or negative value then there is a problem with the fuel control or a sensor input error. If the trim does not cycle around a mid point of 0 the catalysts wont work as it should.

As I read the manual, the values fluctuate from 0 (lean) to 255 (rich). Lambda A seems to always be giving an OK reading (though on the lean side of mid point) whereas B fluctuates between lean and rich. Is this likely to be related to the problem?