nuclear_pond

Hi,

I have an MY99. Car is fine except when started from cold. It sort of hesitates when driving in 3rd or 4th at about 30-40 mph. After warmed up it goes away. Its a bit jerky, but not too bad.

Its almost like its deciding if it needs turbo boost or not, although I cant hear the turbo and wouldnt expect to at this speed it these gears.

Its anoying more than anything. Any ideas?

ta

Blobster

Have exactly the same with my MY99 and thought the same as you.

Once the car is warm, smooth as you like.

Most peculiar.

myp1

this is linked to ur lamda imo.the car goes open loop very early and as such car is still cold.i remember bob rawle saying it goes open loop early to comply with emission regs.in effect its like pushing the choke in too early on a old car

nuclear_pond

so is it a fault that needs fixing, of a 'feature'

ta

myp1

not a fault as such just another impreza quirk(of which there are many)

Matt P

My MY99 does the same. My old Renault 11 turbo did it too. I also think the Scoob's "feature" is related to the HEGO sensor, they go open loop on cold start because they need the exhaust gas to be above a minimum temperature (couple of hundred degs C I think) to operate properly. My bet is that the pulsing we experience happens when the HEGO sensor is just starting to operate and hasn't quite got itself sorted. But I might be wrong. Either way nothing to panic about I don't think.

5 Type R

My MY99 is the same

MelTypeR

iTrader: (4)

Me too.

ozzy

They should all do it. It's due to the O2 sensor taking it's time to get up too it's correct/efficient operating temperature. While it's not, the system easily jumps into closed-loop mode, so you get the pulsing or hesitancy.

You can't remap the std ECU to work around the problem, so one possible solution is to install a Link or Motec ECU, but only if you can adjust the map accordingly. I can't see anyone spending £1600+custom remap time just to cure it.

Wait till the cars warmed-up fully and it'll be fine.

Stefan

5 Type R

Spoke with Nana at Option Motorsport yesterday and he said it was perfectly normal on the scoob

nuclear_pond

ah! big sighs all round then Thanks

Kingsize K2

Exactly the same on my MY99 STiV

Extremely glad to hear it is normal and nothing to worry about Was starting to really bug me!

Leeroy

Had similar problem recently and found the coolant temp. sensor at fault (error code 21 MY97). It was giving erratic readings which in turn meant no cold start fuel enriching, hence the poor cold performance. It was fine when hot though.
Sensor cost me £20ish from dealer, and was a simple fit.

Hope this helps.

nuclear_pond

oooo, so there may be something broke after all then.

submannz

One of my legacy's does this also. Helps so the wife doesn't over rev/boost the engine when the car is cold.

Scott.T

iTrader: (2)

As mentioned above, unless it is really severe hesitation it is down to the Lambda not being at operating temp.

The Lambda does have a heater in it, which helps, but hesitation still occurs.

I have noticed that most modern cars do it. My wifes '52' plate Corsa does it when cold, and so did a lurvley Pegeout MPV thing I drove last week. I think alot of it is down to EU emission regs.

Gridlock Mikey

Crikey, something not being blamed on a failing MAF

Mikey