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[doughall]

Hiya!
After blowing both CATs, I have finally replaced the whole exhaust system.. Thats 2 cats, 2 mid boxes, and a back box. Also treated her with two new Lambda sensors..
Before the cats blew, the engine and everthing were smooth as you like..

Having said that, she now runs very lumpy.. Especially at load at low revs. Doesn't stall or anything, just not as smooth as she was Pre CAT episode.
Just took her out for an M4 trip, down one junction, and back again... MPG is down slightly.. 27MPG at 75 on cruise..

Any ideas? Questions?

[Admin]

No fault codes?

Exhaust fitted and sealed properly?

Check EGR valve is plugged in and idle control valve is seated properly first.

[hotel21]

Not 100% sure, no doubt someone clever will advise, but it may take a few miles for the ECU and assorted brains to relearn the fuelling before running settles down??

Sure the lambda connections are good?

Was it a genuine VX system as some aftermarkets, as well as increasing noise, can restrict backpressure, apparently.

[doughall]

The Lambdas are Bosch...
To be honest, it does sound like an old style "american muscle" type car! :-)
High end revs, my she shifts.. Low end, zzzzzzzzzzzzzzz.....

[Sir Gingerlot]

If the system is not a genuine Vx cat then it can effect running. I bought a cheap Cat for my 2.0 ltr last year. It sounded really raspy, ran fairly well but not as before the replacement and used more fuel. In the end got the cat exchanged. Ran better after that. Other thing to consider is whether the cats have been fitted properly, ie new gasket etc when connected to manifold, as a slight blow here can effect running.

if your are not happy, take it back and discuss with fitters.

[doughall]

Thanks to JamesV6CDX, the DIS has now been replaced.. New Exhaust too, and new O2 sensors..
Runs lovely!
:-)

[JamesV6CDX]

Thanks to JamesV6CDX, the DIS has now been replaced.. New Exhaust too, and new O2 sensors..
Runs lovely!
:-)

Pleased you're happy