When cold the car hesitates at low revs nut stops doing it when warm & is no problem at all at high revs/boost. Any ideas/similar occurences?

Cheers

MAFFA

 

mine seems to do the same first thing in a morning i think its natural.

 

Never done it before last weekend. Drove back from Chelmsford & the next day it was doing it?

 

Not sure why they do it but over time and completely out of the blue Subaru's seem to develop this problem and to this day I am unsure of the fix or if there is even one.

One thing it could be is the knock sensor, it is a known problem that they can get too sensitive and it causes the engine to retard when cold because it thinks it is hearing knock. Most likely to be picking up mild piston slap, valve noise, or tappets of course until the engine warms up.

 

never had this problem as i keep mine under 2500 rpm till its warm..

thought that trying to boost on a cold engine/turbo would eventually end in tears

 

MAFFA,
will have to check your MAF sensor - could be a nickup. whats the lamdalink doing whilst this is going on ?

Steve

 

I think my post might have read wrong. I wasn't boosting on a cold engine but it was still slightly doing it when warm. Only when I booted it did the hesitation stop on a warm engine. It was worse when I was on low revs on a cold engine.

Steve - the lambda wasn't doing anything unusual.

Funny thing is the car seems to be fine now. I took a drive to Bedfordshire at the weekend & in case I couldn't find a Shell I took some octane boost with me. Filled up on Texaco Super (on my return) plus the octane boost making it about 99Ron and it was fine. Gone through 1/4 tank so far & there's been no problems so far.

Could I have got some dodgy fuel or something as I always fill up at the same Shell garage?

I'll keep you posted if it does it next time I fill up with Optimax.

MAFFA

 

Mine does it, usually for about a week, then the problem clears up, then it comes back. I have no idea what causes it though.

 

Must be one of those "unknowns" that we'll just have to live with every now & then. Lets just hope it's another 2.5yrs before it does it again LOL

MAFFA

 

I managed to smooth mine out by adding extra earthing (earthing mod).

Worth a try..

JGM

 

MAFFA,
My own 1999 UK turbo is doing something similar to yours. Mine hesitates below turbo rev-band, almost like a mild flat spot, but mine is "cyclic" in nature. It is worse when cold but does it slightly even when warm.

But like yours, when the turbo comes in, its all dissapears and smoothens the whole thing out.

Somebody told me to change the plugs and it should fix it. Haven't got round to it yet. This might not be any help to you, but if your plugs are old, it might be worth a try.

 

the cyclic is normally the ECU rocking the mixture around stocih (sp?) 14.7:1 ...
on boost it just chucks fuel in & therefore doesnt care.

might indicate a nackerd (or nackering) Lambda ... ????

Steve

 

If you search for hesitation or surging you'll find that this is a common problem (if it's the same thing we're on about). My MY00 also had this problem. Changing the ECU from a 802 to a 801 helped slightly. Changing the O2 sensor made no difference, however, running the car with the O2 sensor unplugged removed the problem entirely and the car runs like a dream. I'm currently seeking advice as to weather running the car with this sensor unplugged could be harmful, see this thread http://www.scoobynet.co.uk/bbs/thread.asp?threadid=243085
Seeing as most of my driving is done with short journeys and the car not being given chance to warm up it makes my driving experience better but if you do long journeys and the car just plays up when cold then I'd just live with it until it warms up.
Regards
FC

 

My MY94 UK done it when I ran it on Optimax. Was fine on BP or Esso and even better on normal UL and a dose of NF.

Although my MY00 prefers Optimax.

Probably something to do with the better timing control in the later ECU.

 

have you checked your water temperature sensor? (under the inlet manifolds i think) if this fails, the ECU sees the engine temps as hot and doesn't use choke when you first drive the car from cold

i'm pretty sure this is the case, but don't hold me to it


kev

 

When the coolant sensor fails it adds the extra fuel for the choke and puts the fans on in case the engine is hot.. as the ecu has no idea whether the engine is hot or cold so covers both situations. Indicator being the fans on when you first start it and drinking even more fuel than normal.. and there would be a check engine light error code with it.

JGM

 

Changed the water temp sensor a few months back coz mine was buggered. Pain in the ar$e to change and had to get my girlfriend (with smaller hands ) to help LOL