For the past week, my MY93 WRX has had some hesitation problems. I'd been experimenting with the bleed valve, but had put it back to it's original setting. I had previously been acheiving 12psi boost held with the occasional burst to 15psi.

I have always had symptoms resembling that of overboost, but now I have the gauge fitted, it appears not to be that.

Now the boost seems erratic in it's figures acheived, sometimes 9psi, sometimes 12, sometimes 15, but the common feeling is that of either a slight hesitation, or sometimes a full blown "brick wall" effect followed by a backfire at between 4500 and 5000 rpm.

I run the car on Optimax only and it certainly doesn't feel or sound like it's pinking.

The car has a full Scoobysport system (excluding up-pipe) so is totally cat free, plus it has an HKS "mushroom" induction kit.

Does anybody have any ideas?

Also, while I'm asking questions, do all Scoobies grind into reverse, or is it just mine? Tried double-declutching etc, always grinds, even when first started.

 

could be a MAF fault mate,try fitting another one(from a friends if pos)

 

I have no friends with Scoobs, that is