Hi ALL, My MY99 Impreza Wagon non-turbo has developed a flat spot on light throttle position, suggestions please on where to start looking for the problem.

 

Deafening silence! .. hasn't anyone experienced this before then....🤔

 

No one owes non turbo impreza

 

https://www.honestjohn.co.uk/forum/p...ex.htm?t=59112

 

Ignition. Spark plugs, coils etc.

 

Please allow me to elbow my way in here with what I think is a similar problem.
MY15 WRX STi.....when accelerating hard through the gears there is a slight hesitation at about 3200 RPM for a split second then carries on as normal. I've actually noticed this for a few years now which is mildly annoying and just wondered if any others with a similar model has experienced this?
Mileage is now 80K, serviced regularly at an independent and drinks Tesco 99.
Any thoughts would be appreciated.....thanks.

 

You're welcome! May as well keep this thread going. This is what I think might be happening in your case as I've got a TDCi Mondeo, and THAT had the self same issue at 3k revs. It was a split in a turbo pipe,. The split kept closed till boost pressure forced it apart which resulted in a momentary loss of boost which resulted in the hesitation, but then as boost kept increasing it overcame the pressure loss.The boost pipe, being thick rubber, the split isn't obvious and takes some squeezing and twisting to reveal it.

 

Google " GR Grumble" which should explain this flat spot in 2009 onwards impreza sti. It's caused by oscillations in the fuel delivery, as the damping method was changed as the new range of impreza came in. It is worse on modified cars, and occurs roughly between 2800rpm and 3500rpm, particularly whilst accelerating from 4th, 5th or 6th gear, if you fail to drop a cog before acceleration.