Hi all.My mate has just baught his first scooby today wehey .Its an Impreza Turbo 2000 uk on a V plate.The car as we know it is in brilliant condition with a full service history,loads of recipts and running compleatly standard apart from a Mongoose back box.We were driving around as you do the day you purchase and noticed there was a bit of a flat spot in the rev range.When he was in say 3rd and stuck his foot flat to the floor for a hard pull the power would come in nicely for a short time but then die off for a thousand revs (only very softly though) and then come on strong again.Its nothing harsh like a fuel cut or anything like that it just seems to be very soft hesitation.When lightly accelerating in any gear it can hold the boost really well and pull cleanly right up the revs,but as I say only on light throttle.
You can hear the turbo spool up but then die off when we hit this "flat spot" usually arround 4.3k revs then spool up again.
Could it be a leaking boost pipe?
Faulty actuator struggling to hold boost?

Any info would be greatly apreciated

 

Sounds like possible MAF trouble to me, rough idle and/or 4k flatspot. 98-00 cars are famous for it as they use a hotwire MAF sensor. Either get it looked at by someone with diagnostic equipment, or do an ECU reset (do a search - tip....either by using connector blocks under steering wheel or disconnecting battery for 1/2 hour) which will highlight the failing component. The ECU adjusts to compensate as MAF's degrade over time, making the problem hard to recognize, but an ECU reset makes the ECU expect the correct parameters and thus should throw up a fault code. MAF can be had for IRO £80-90, but don't be fooled into buying the housing along with it for £200+.

 

It sounds like it is knocking some timing out at this crucial point due to knock.

edit to say it may be fixed temporarily with an ecu reset as it might have been through running it on some dodgy petrol. try a reset first and see whether it stays like it.