scania dave

my sti 4 started juddering when under load,it was diagnosed with a lamber fault,three sensors av bin tried but it is still the same,as anybody any advice as the garage has ad the car for two wks and its killin mi

greasemonkey

If the juddering was occurring under boost/load, the lambda sensor is one of the least likely causes. Suggest you take it to a dealer/specialist who knows what they're talking about!

Could you describe to us exactly what this juddering is like, along with the ncessary background about your car - does it occur in all gears? Does it occur (or is it worse) at a certain engine or road speed? Are you using a KnockLink, and if not, what fuel are you using? We can't help you without knowing things like that...

scania dave

the car was fitted with a boost controller,stanless ex and a hks filter at rc developments,the check warning light kept coming on and they told mi to disconnect the lamber,a not very helpful bunch after takin the readies,that was about six months ago.about a month ago it started to hesitate then judder through the rev range,as if it had either a fuel or air starvation or even a breakdown in the electrics only when the boost was turned up and i put the foot to the floor,over say 4000 rpm ,normal running it was fine,it slowly got worse till it was doin it when on normal boost and idle became irratic.its in a specialist garage now for 2wks and they've tried leeds,coils,fuel pump,but it keeps comin up lamber fault on the lap top,bein in the game am itchin to try an sort it,there trying to borrow an sti 4 ecu to c if it cures it,they seem gd lads but think there runnin out of ideas an am runnin out of sanity. by the way its in all gears,any road speed,knock link not fitted yet and its runnin on optimax. thanx for ur reply.

redwrx

Ive got an MY93wrx, and that used to stutter under load, altho only intermittantly,

Im not sure, but have they considered the MAF sensor (the one on the air intake) a failing sensor, can make them run like a bag of crap, or alternatively on the MAP sensor, my pipe had come off that, when i put my MBC on, and i hadnt noticed, this kept bringing up the CEL, every time i came off boost.

I ad my Lambda sensor fail, i only realised when i but an AFR meter on, and it wouldnt work...so how long my Lambda was sown for i dont know... but i dont think it was the cause of the stuttering.

Hope these give a couple of new angles to solving your problem.

Frank

greasemonkey

It's very unlikely to be a bust ECU Dave. These either tend to work 100% or not at all, so the likelihood is that your own is fine.

As Frank says, the airflow meter is a likely suspect, as would be a leak in the pipework somewhere between the air filter and throttle body (i.e. induction pipe/y-piece/intercooler to TB pipe.

Using Optimax alone on this car is a really bad idea. Even if it was standard you should be using booster, and the need is especially pressing given that you're running increased boost levels and presumably a cone filter.

Speaking of which, have you tried refitting the standard induction tract and reconnecting the standard boost solenoid to see if the problem goes away?

scania dave

thanx for ur help and advice guys,a new air flow meter has bin ordered at £400 and the hks filter is being removed,soon as i get her back i'll b raisin the octain level with additive,just hope that this cures it or al av to put the misses on the game,thanx again.