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Boost problems & idling

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Heres the story so far.Got the 1999 classic turbo with aftermarket cone filter.running fine.Changed oil/filter/fuel filter.Running fine.changed plugs and went back to oem filter with genuine Maf.Now when idling every 5seconds or so it engine changes note,only very briefly and so on and so on,engine appears to have little shake everytime this happens,where as before it was just totally still.Removed plugs and gaps are all 0.8.Changed coil pack and ht leads for 2nd hand one which I know are fine.


Still the same.Also if you put your foot down hard from slow speed-its hesistant and like its holding back for a millisecond or so and does it quite a bit..But higher up speed its still goes ok.Cleaned boost solenoid today and still the same.Does throw up code for faulty maf now and then but tried a friends genuine one today and stil the same.Getting a bit cheesed off with it now-cant find any leaks from hoses anywhere but this all seems to stem from when I changed the plugs?They are PFR6B's ngk.Have checked them again today all appear to be fine.Any Help appreciated :( :(


Anyone local to Lowestoft/Suffolk or Norfolk etc

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Hi jay,i'll try that.But when I had it for a couple of months on that set up,it ate 2 mafs,so that's why I put standard box back on.As far as I know its got standard ecu.But i'll give it a go though.Its a k&n cone filter and yes it had a maf with it on pipework.

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I don't know of it's the same with Imprezas as Legacies, it probably is.

To a certain extent, you can make your ecu learn about minor changes. I suspect the ecu dosnt like the air filter change having learnt how to cope with the aftermarket one.

In a Legacy, the way to make it re-learn is as follows.

Disconnect the Battery for an hour, then re-connect.

Go for a steady drive off boost. Make sure you use all 5 gears.

Turn engine off, re start and it should have learnt.

You can't do any harm doing this and it may work.

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I think most people run ngk7's gapped at 0.7

We're any of the plugs a slightly different colour ?

If one was blacker it might indicate a misfire on a individual cylinder .

Did you check for cracks in the porcelain on the plugs ?

It will throw maff and (normally) map sensor code as well if there's a leak between maf (filter) and map (inlet manifold) sensors .

You could try putting soapy water around the joins in the pipes and look for bubbles to indicate air leaks to eliminate that .

Tbo you've checked most of the things I would have started with .

Mabye nip to attowes rolling road (norwich) and get a dyno done , as he'd probably be able to diagnose the fault and you'd know if it was running safe .

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It did have ngk  Bkr7eix in when I first got it,plugs were ok when I removed them.Might pull out the 6's and put the 7's back in as I still have them and see what happens....Failing everything else might be a call to clive attowes then

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Well I tried swopping back to cone-no joy,so took plugs out and replaced with 7's.Plug 3 had a crack in it! fire up motor and idling properly.So put oem airbox back on and still idling properly.No fault codes.Took for a 2mile run and hesistation gone and touch wood everything seems fine.What model plug would you use as I put back in the bkr7eix's and checked gaps all 0.7. :)

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