V7 sti boost and misfire issues.

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Hey guys, I have my v7 sti and my mates v7 sti and both of them have an issue..

My v7 sti: Just had a replacement engine and when i'm just cruising up my hill not boosting I get this slight misfire feels like a fuel related issue but i could be wrong, also my Air fuel gauge drops and comes up every time it misfires and it's in sync to the misfire which is why i thought it could be a fuel issue.. On boost it doesn't hesitate at all.

Mates v7 sti: Mates v7 sti hesitates on boost, he's got a gfb electronic boost controller and we've noticed that on a lower boost setting the misfire is worse but on a higher boost setting it's a lot better but still has a misfire.

Any ideas what these issues could be related to? Quite tempted to swap over parts to find out the problem, any help is appreciated!!!

Thanks in advance!

[Marky]

A dozen different things could be at fault

Could be spark failing - try new plugs or even simply gapping yours closer to rule that out

What is modified on them? Are they stock cars or do they have a half dozen changes?

Ignore the air fuel gauge

Have you plugged a scanner into them

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No haven't plugged a scanner into any of them, both fairly stock..

[Marky]

Define "fairly stock"

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 Marky said:

Define "fairly stock"

My sti only has a bov and my mates one has bov, 3" exhaust, gfb boost controller, pod filter and a tune.

[Marky]

Small chance it's the bov having a slight leak - almost all piston-type ones will simply cause you can't make brass on ali a perfect seal

Might be the afm being dirty

Might be old spark plugs

Might be something not tightened up right on reinstall (like intake hose - pressurised and not)

Might be the fuel pump being sad

Did you ever find out why the old motor went pop?

You mates one could be a number of things. First suggestion is go back to whoever did the tune, also they are very touchy around airflow meter adaptors and the way it flows through them - simply changing the angle of it or putting a new bend before or after it can mess with it