02 Forester XT boost hesitation/surge

[CaptainH]

Seemed to developed a slight boost issue with my forester xt 4eat 

 

Can hear the turbo spooling but sitting at say 90kmh and go to pull out and pass the turbo initially boosts but drops off a small amount before coming back on full boost does it at about 4000rpm

 

Won't do it from standstill when u boot it 

 

Car is stock apart from a perrin turbo inlet tube 

 

Any ideas it's not hugely noticeable but still annoying, kinda feels like the gap u get in the twin turbo legacys 

[Loren]

I'd check the plugs and leads.

[CaptainH]

9 hours ago, Loren said:

I'd check the plugs and leads.

 

Just had new plugs not long ago and replaced 1 new coil hopefully the others are still ok

[Loren]

1 hour ago, CaptainH said:

 

Just had new plugs not long ago and replaced 1 new coil hopefully the others are still ok

 

What gap did you set?

 

So coil on plugin is it?

 

It sounds a bit like it could be mis-firing from what you have described. 4000 rpm is where the boost will be coming on very quickly, so peak torque... possible over boosting a bit and the spark is breaking down. Though I'm not sure how likely that is with coil on plugin.

Edited October 8, 2022 by Loren

[CaptainH]

6 hours ago, Loren said:

 

What gap did you set?

 

So coil on plugin is it?

 

It sounds a bit like it could be mis-firing from what you have described. 4000 rpm is where the boost will be coming on very quickly, so peak torque... possible over boosting a bit and the spark is breaking down. Though I'm not sure how likely that is with coil on plugin.

 

Yep coils, I never touch the spark gap when doing plugs ...

 

Interesting it's very slight and not violent boost drop, could be the coils as it's done high kms now - 240kms

[Loren]

You could close the gaps up tight to see if it helps. 0.018 would be as tight as you'd want to go.