Hopefully someone will be able to shed some light on this - don't know what to check next!

My JDM STi v4 hasn't been right for a while now, intially had a MAF sensor go so replaced that with one from a breakers, had it on a rolling road (Clive Atthowes) and discovered the Lambda sensor was also gone, so that's now been replaced too. Also replaced the fuel filter.

Both sensors appear to be functioning correctly now, however another trip to the rolling road has shown the car is still running dangerously lean in the low revs. There wasn't time to diagnose the problem full while at the garage, and it's a long and expesive journey to get back there so am hoping to be able to figure out something myself first.

Any ideas what could be causing the fuel supply problem? Replacing the fuel pump is an option but I don't want to keep chucking money at guesses. She's had a de-cat exhaust and induction kit but no other performance related mods - could it be possible that it's a mapping issue? Any help much appreciated

Cheers.

 

Most probably you need remaping or a fuel computer in order to compensate fuel to the extra air entering the engine due to the induction kit.

 

I agree - unless the car has been mapped, the free-flowing nature of the filter and de-cat will make the car run lean. You could get away with just fitting a better fuel pump (walbro 255lph) and an uprated fuel regulator, but ideally the car should be re-mapped to get the best out of the mods.

 

Ok cheers for the advice guys. If I was to go the easy route what fuel regulator would you recommend and how much are they?

I've heard remapping is a problem for pre-99 cars due to the old ECU type? If so, how do I get around this problem - do I need a piggy back ECU or is there another solution?

Sorry for all the questions, my first scooby so am still learning the ropes Cheers.

 

There are replacement ecu's which can be remapped like Apexi PowerFC for example

 

Power-FC is a good choice but also you can do a good job cheaper with a Greddy E-manage blue. Or even easier with an Apexi S-AFC, fuel only though, no ignition adjustments.