Andy03STI

My 03 Sti acceleration on part throttle is very lumpy like misfire between 2000-3000 rpm. Terrible when it's cold. It seems to be as it's coming on boost. Also worse if you having steering turned i.e when turning at lights or on a roundabout.
I've checked all pipes, cleaned idle control valve and boost solenoid changed plugs but no better.
Does it sound like a maf going down? Or can coil packs cause these problems?
Any help appreciated.
Thanks Andy

MalcB

Seems to be a fairly common issue. Could be anything. From O2 sensor, MAF and even neutral position switch through to plug gaps, coil packs etc. Sorry but think it's going to a process of elimination. You havn't got a CEL light yet ??

Andy03STI

No not had cel light on at all. Had problem for few months now.

ALi-B

iTrader: (1)

Very tricky. Its possible. A sluggishness/holding back at around 2000rpm is a known symptom.

One thing I have noted on many cars (not just Subaru) with a MAF on the way out is inability to hold a steady fast-idle.

Say 1800rpm. You should be able to get the throttle in a single position and hold it there without changes in revs. If the revs die off and you have to use more throttle to mainatin 1800rpm, then find your self suddenly overshooting the target rpm. Then it is often a sign the MAF is not reading in a linear fashion (or there is a vacuum/induction pipe leak/PCV fault).

Sadly the only sure fire way is to compare live data with somone who knows what values it there should be. Or exchanging the sensor for a known good one (not one off a scrapper) and resetting the ECU learning parameters.

Andy03STI

I turned into work today and put foot down while turning and it really stuttered. It seems to be when there is extra load on engine i.e steering pump working harder the problem is a lot worse.
Problem does not do it everytime.

Andy03STI

Problem sorted. Bought new maf and all is well.