Poor running after exhaust fitting

[Alias]

Had a new OEM exhaust fitted back in April after the old one rotted away, noticed the other day that it had started to blow a bit. Took it back to the garage that fitted it and they said it needed a bit of welding and done it under warranty as its only a few months old.

I thought it would be the end of it but its now sounding a little odd, not blowing again but definitely doesn't sound right - I know its idles a little rough anyway but almost seems to exaggerate the noise and also smells like its running really rich (both on first start up and after a 150 mile journey last night).

My thoughts are they've either just completely bodged it as its was a warranty job and they're not making any pennies or they've twatted the lambda sensor thingy making it run rich.

Anyone got any other ideas what it could be so I can go shout out them and make it look like I at least half know what I'm talking about.

Cheers.

 

[MartinR]

Would say lambda sensor myself. Where abouts was it blowing?

 

[Alias]

Sounded like it was coming from the back box, just checked through the receipts and they only changed the back box in April so figured the weld must have been there if they fixed it under warranty.

Guess my next question is does anybody have a code reader near Thetford? presume if it was the sensor it would show up on there?

 

[dave_rudabar]

If you can get under the car to look, the new welds should be fairly obvious.
FWIW, my pattern zorst backbox was always a bit noisy, not that much quieter than the rude-boy Powerflow one it replaced.

 

[Alias]

Cheers Dave, I'll try to have a look tomorrow but haven't got my axle stands at the moment and don't really fancy sticking my head under when its only held up with a jack, I'll see what I can see just as she is. Problems not so much the volume just that it nows sounds really sh!te - far worse than it did before, even when it was blowing.

 

[Alias]

Had a look under the car, you can see the welding done on the exhaust;

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its been welded like this at both ends of the back box but that was all that I could see.

Also took this to show how rough it was sounding;

 

[Dan519]

that welding has been done at the factory

 

[Alastair.]

Thats not oem, doesn't look like it to me anyway.

 

[Alias]

Been doing some investigations.

This type of exhaust was originally fitted in Chelmsford in Dec 2011.
This was then blowing in Apr 2012, we had since moved from Chelmo so got it replaced in Thetford. Since it was only a few months old the Chelmsford garage said if we sent them the faulty part they'd at least get it fixed or a replacement sent out. So the Thetford garage fitted a new one and we sent the knackered one off to Chelmo to be replaced.
Now the Thetford fitted one has had some welding done (although not sure where since, as Dan said, the newer looking welds are probably factory fitted anyway).

anyway, after a few days a lightbulb flickered into light above my head, the replacement from Chelmo is still in the shed so dug it out and this is what is fitted to the car...

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I've done a bit of googling and RN904X seems to come up as standard for a 172 so don't know if its correct or not. I'm guessing its cheap and nasty but if anyone can let me know if its complete toss or just slightly poo? I'm guessing complete toss since we keep needing to weld or replace them!