Occasionally when changing gears from 1st to 2nd @ 6000 the rpm needle will drop to zero & bounce back to about 4000/4500 rpm. Sometimes when changing from 2nd to 3rd gear too.
I have notice it only happens when driving hard & changing gears at high rpm.

Anyone got any ideas as to why this is happening?

Thanks Ticky

 

isn't that possibilly an indication of a fault maf? especially if its a MY99 / 00.

do you have a knocklink?

stevie

 

Everything gets blamed on the maf ... lol.

If you have an early car then this is probably down to interference in the car wiring making the tacho jump, related to grounding, not unusual but hard to stop. Even in a MY99-00 this can also be the case but not as common.

The Impreza wiring looms are susceptible to ground looping and ignition spike interference.

bob

 

Thanks guys.

My maf is fairly new only 3000 miles.
I thought it had something to do with the anti hi-jack. Possibly this is causing the interference.
Thanks Bob for clearing that up, at least I will now not to fix it & better just living with it.

 

I would try and fix it. Could be caused by bad coils as cracked coils will cause interference.

 

All four coil pack are nearly new, 1500 miles on them.
Will try the earthing mod, see if that helps.
I will check with my alarm installer, to find out if the anti hijack is connected with the rpm signal in any way?

 

if they have.. then that'll be why. it needs to be a faily high impedance otherwise it will make it go all over the palce.
Steve