My car seems to have developed a backfire this week. It has done it before when pushing on, changing gear at high revs and boost but now it had started to do it more often.

Seems that it does it when on part throttle, if I take my foot off the accelerator just before it starts to boost I get a pretty loud bang out the exhaust.

Any ideas what could be causing it or how to stop it?

Car is running a VTA BOV as it has a a FMIC but was mapped in that configuration. Only recent change is fitting a swirl pot but cant see that making any difference and it was fine immediately after fitting.

Cheers

Arthur

 

Arthur, please tell me that your avatar is NOT your bird?!!!

 

Before we crack on, you weren't really low on fuel and going round a corner when it happened? Just gotta make sure we get that outta the way, first.

 

Joz, unfortunately no to the first question!

To the second, no not going round a corner, can pretty much get it to do it on order, apply the throttle, lift just before I get positive boost, lift off and bang!

 

isnt it just petrol igniting in the hot exhaust ?

 

Yes but why is the petrol getting into the exhaust? It hasnt done it before?

 

Could it have hit overboost

 

Nope, it is fine when driving on boost, it happens if I come off the throttle just before it starts to boost (when the boost gauge is showing 0)