Misfire and maybe down on power any ideas?
 

Hi all,

Another eratic intermittant problem cropped up on the scooby this weekend.

Was driving around, normal traffic, circa 30-40mph, no hard driving and the car developed a hell of a stutter/misfire. Seemed to clear itself after a minute or two and hasn't reappeared.

Was a really hot day which it hasn't been in a while so wondered if that could play a part?

Then i get to thinking, the other night, having a bit of a spirited drive, it felt a bit like it was down on power, not quite as quick as normal and a bit hesitant building/boosting. It also let out a big haze of i'm not sure what - not quite smoke but like that this last week whilst on full chat and changing gear.

I've noted some oil in intercooler pipework when changing turbo oil feed line and again the other wheek when i had the intercooler off to fit a turbo blanket.

Mods -

FUlly forged engine
Remap
Decat down pipe
Forge BOV

ANyone had similar symptoms and can offer some starters for 10.

I've read plenty of other posts across google and i would like to have a crack at solving it myself to save money before having it back to the garage again.

My thoughts are

HT Leads
Coilpacks
CTS
Boost Leak/VAC Pipes (anyone got any tricks to spot boost leaks?)

anything else? I hate the idea of it being more serious given the engine is forged and by a reputable builder a little over 15k ago.

Any help would be appreciated.

ps anyone used Kamikaze racing in Minworth? they seem new and local to me so likely the closed subaru specialist so the car may end up there.

Anyone got any ideas?

Symptoms, hesitant and jerky around 2k rpm and i can't hear the boost building like before, though once on boost drives ok, bit of unburnt fuel haze out the back but no black or white smoke. Feels a bit lumpy and rough generally.

No CEL thrown but will get obd2 scanner today so will fault code read tonight and post back.

thanks

What model and year is the car and i would get rid of the BOV.

year is 2006 on 56 Hawkeye STi EJ25.

Misfire seems very intermittant

Still feels a little down on power.

Waiting for OBD scanner in post today and then i'll code check it but as said no CEL thrown.

Down on power and no CEL could be the NPS.

Other things you might want to check are the spark plugs and PCV valve

Could also be bad fuel or fuel pump

yea had very similar symptoms, was a cracked piston, sounded like big end knock on start up which went quiet then similar symptoms to yours. when stripped engine down only thing holding piston together was the rings, still got the piston as a momento! hope it isn't same for you
do a leak down test, see if one cylinder is down

could be something as simple as a loose plug, so dont take what i said too seriously until you've checked the basics

So no codes stored or thrown after a drive but got some data logged but nothing i can see untoward.

I would hope its not piston failure as its got Mahle pistons and rods done as part of a forged build less than 15k ago...never say never though.



whats the NPS dude?

I was personally thinking bad fuel or clogged injector or maybe coil packs but what about VAC leak - removed intercooler couple of times recently including BOV - used same gasket didn't replace as looked fine.

NPS=neutral position switch.

Front lambda

Check your turbo to intercooler pipe, it can be a tricky one to get on the turbo securely. I've seen them where they look like they are on. But when you take the intercooler off for a proper look you sometimes see they aren't as snug as you think or sometimes they have a kink in the lower side where it hasn't slipped over the outlet.
This would certainly give the problems you're mentioning, and would tie in with the fact you say you had the intercooler off before the issue started, definitely worth double checking you have got it on 100% before digging any deeper.

Well no codes and the car is boosting better but i think that is becuase my turbo blanket popped a connector and was fowling the wastegate arm - d'oh!

But still a bit lumpy around 2-2.5k where its just driving very slightly off boost in normal traffic.

I've been running torque pro and can see a very slight fluctuation in vacumn - the numbers change at idle between 19 - 21 in/hg - could that indicate a leak?

I've got it booked in with TDR (where it was built/mapped) on 22nd so see what is what when i put it on the dyno. Get it running properly and then maybe see about tweaking the map maybe.