Exige S2 Cat Bypass - Rough Idle

[427blue]

I recently installed a cat bypass on my N/A Exige S2 and it's caused the idle to run rough.  Idle cycles by dipping to almost stalling then swings up to 1500rpm then back to normal.  Bypass is running with a Stage 2 exhaust.

 

I've reset the ECU and have ran the car for a few weeks now in the hope its just re-leaning but no improvement.  Decided to fit the cat back on yesterday to see if the bypass was the problem and car has returned back to normal idle straight away.

 

Has anyone fitted a bypass and experienced similar problems.  It's only the idle that's the problem and there's no problem once on the move.

 

Thanks

 

Graham

[Bibs]

Are you sure you reset the ECU correctly? It should be ok with the cat bypass, can't think off the top of my head why it wouldn't run ok without the cat. Is there an easy way to reset the IACV too as if it's hunting, perhaps it's out of the range it can handle...

[427blue]

Hi Bibs

 

Thanks for your reply.  As far as I know I reset the ECU correcly (press / release the accelerator pedal whilst the key is turned to ACC).  Also had the battery disconnected whilst fitting the bypass which I believe also resets te ECU.

 

Not sure about the IACV and how to reset it but will have a search.

[Bibs]

I've asked a knowledgable friend and the issue is that the Stage 2 exhaust is specifically for the supecharged cars. You need a Stage 1 exhaust which is specifically for NA cars. That's the problem mate, your back pressure etc will be all screwy, exacerbated by the de cat pipe.

[427blue]

Thanks for the info Bibs.  Didn't realise the Stage 2 was for supercharged cars.  It was fitted when I bought the car and it runs and sounds great.  I'll leave it on along with the cat.