EdGasket

So why would you need to reset the ecu? Could make emissions better or worse couldn't it depending on how the ecu reads the sensors. Also is that 100% right about just letting it idle because then the ecu is only going to see 'idle' values? Surely you should take it on a normal drive so the ecu can learn the full range of values from each sensor; Just my thoughts. ECU cheat method for downstream O2 sensor is shown in this video: It's just a low pass filter to stabilise the second O2 sensor output so it doesn't track the upstream sensor (indicating cat not doing much) and avoid a P0420 error. Has the advantage of not having to remove a rusted in O2 sensor but you will have to break into the wiring at some point.

Thanks I know about the spacer/defouler trick with the lambda sensor. OEM cat sounds £££s; will it make much difference on a 1.4; not interested in performance; just cheap motoring. How do you 'reset the fuel values' and what are they? I have an OBD2 reader which will reset the CEL. Also any advice on reaching the downstream O2 sensor to fit the spacer and unhooking the wiring which seems to go straight up through the floor? As a spacer alternative, you can fit a simple filter - resistor and capacitor once you have got to the wiring.

Hi, my MB2 Civic which is OBD2, has an exhaust rattle which I believe is internal to the cat; I notice it when the engine is revved, pulling away etc. (Have checked heatshields which seem OK). The car has also thrown a P0420 (cat efficiency) code and if I clear it it usually comes back within 50 miles. The MoT is due next month so I am not doing anything before and will see what the emissions are like; but if I do need to replace the cat, are the cheap cats on eBay and from EuroCarParts for about £60 any good e.g. HA8002? Will they do the job and prevent the check light coming back or do I need to spend more on a better cat? e.g. http://www.ebay.co.uk/itm/CATALYTIC-CONVERTER-CAT-FOR-HONDA-CIVIC-1-4-1996-1998-HA8002-/331682519400?hash=item4d39d19968:g:O24AAOSw14xWH98N Also how do I access the connector and wiring for the downstream O2 sensor; is it by removing the centre console? Is that straightforward or a pain?

Does manifold wrap help with slightly leaking exhaust from a cracked manifold (this is on a Hyundai with a cast manifold) or would it just blow/burn straight through? The leak is not enough to have been spotted at MoT or to cause the emissions to fail.