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View Full Version : Aftermarket catalytic converter problems!


Simon.h
3rd September 2011, 16:34
Hi all,

As you may all know i bought my 2nd ZT in April with 1 weeks mot and a lpg fault. Within the 1st week i got it moted, the mot tester said it only just passed the emission test (it was running on petrol due the lpg not sorted yet)and would fail next time if still on petrol.

Ive also had fault code PO 420- Catalyst system efficiency below threshold, so ive been over the last few mths swapping the 02 sensors around, clearing fault code and rechecking but it always comes back. So its 100% its the cat at fault!

Then i could hear a exhaust leak from low down behind the rad, turns out the cat had a crack in it.

Well i got a cat from Ray Squires (cheers Ray) and today went about changing it. The cat looks like it been replaced just before i got the car and looks like a aftermarket one-

Heres the new and old one, the one on the left is the cat i removed(aftermarket one) in all pics.
http://i744.photobucket.com/albums/xx85/simonhouse06/MGZT190028.jpg?t=1315066787

Notice the different in the pipe as it enters the 1st cat.
http://i744.photobucket.com/albums/xx85/simonhouse06/MGZT190029.jpg?t=1315066986

Notice the hole for 02 front sensor is in different place, this makes the wires on the sensor rest on the sump.
http://i744.photobucket.com/albums/xx85/simonhouse06/MGZT190030.jpg

And the crack running around the same sensor and up the down pipe.
http://i744.photobucket.com/albums/xx85/simonhouse06/MGZT190031.jpg
So if you need to change your cat maybe worth thinking about a good 2nd hand one not a aftermaket one!

Simon.h
4th September 2011, 07:47
Well i cleared fault codes and so far none have returned!

Dave Goody
4th September 2011, 09:39
I bought an aftermarket one from Partco as there was several hundred pounds difference between that and OEM. It does suffer from resonance at about 2,200 rpm I sent back and had another the same fitted and same resonance. So decided to live with it:} Cheaper ones dont seem as well built
Dave

Simon.h
4th September 2011, 15:12
So aftermarket ones can - crack, not do their job and throw up fault codes and cause some resonance to engine!

Has anyone else had problems with aftermarket cats!

rizel23
4th September 2011, 15:16
do you need a cat to pass MOT on LPG?

Simon.h
4th September 2011, 15:25
No you do not!

A lpg car will pass with out one! as long as its running on lpg! which mine was not at that time!

rizel23
4th September 2011, 15:27
No you do not!

A lpg car will pass with out one! as long as its running on lpg! which mine was not at that time!

wahey, if mine goes i shall leave it off then!