hodgey001

I have bought a my99 impreza turbo when i boot her after 4000 revs it hesitates to go more it still accelerates ok but no where near what it should be any ideas

Diablo

There could be a many different reasosn, but it sounds like the inbuilt boost cut issue - all MY99 cars do it.

If you hold highish revs (around the 4,000 you mention) and accelerate in a low gear, you don't get full boost until you change up.

Right pain in the **** when, say, exiting a second gear corner.

Either change up early, or let the revs fall a bit before accelerating.

hodgey001

How do i get by this crap

New_scooby_04

iTrader: (4)

You don't!!! It's related to emissions regs, even the ECUTEK mappers can't map it out!!

I'm guessing an aftermaket ECU might take care of it though???? Any power FC users out there care to comment?

Changing your ECU to get around it might be a bit drastic though , just lift off slightly and then press it again.

All I would say is that you should be careful that the "hesitation" you mention isnt a sign of your MAF on the way out (how's your idle?). boost cut doesn't so much cause the car to hesitate as much as not go with the conviction that that it otherwise would. Boot it with a failing MAF and it's good bye engine!!

Ns04

jaytc2003

iTrader: (1)

you cannot get around what Diablo says. However due to the year of car that you have, it is more likely to be a maf sensor issue.
At or over 4000rpm does it feel like it is missing a bit sor tof holding back?

A good check is to have your car idling and disconnect the maf sensor. If the car continues to run then the likelyhood is that this is faulty. However it can still be faulty even if the car cuts out so its sort of a 50/50 test.
Also a possibility could be the plugs. At around those rpm you would be running full boost (assuming foot planted to the floor) and it is possible for the spark to be blown out.

New_scooby_04

iTrader: (4)

Unfortunately, I recently learned from Bob Rawle that it can happen in any gear, but is most likely in 2nd. It is a complete PITA, and IMHO quite dangerous- but when you know its there you can drive around it.

Ns04

hodgey001

whrere do i get a maf sensor from

hodgey001

whrere do i get a maf sensor from

jaytc2003

iTrader: (1)

subaru, for your year of car they are about £70 ish. Best to buy new so dont get one from a scrap yard. Quite a few people change them annually on the my99/00 cars.

Dont just change the maf though without diagnosing the fault first, as I have said it could be an old set of plugs causing the problem// leads breaking down etc.