TURBOTRONICS

My classic 94 wrx has developed a bit of a problem that is really getting on my nerves now
Over the last 12 months it’s started having a problem with juddering when cold between 2000rpm and 3500rpm and over time its getting worse.
It starts fine in the morning no matter what the weather but when you set of for the first few miles it stalls at junctions and when you get to about 2000rpm it starts to judder and the more you put your foot down on the accelerator the worse and harder it gets till you reach around 3500rpm and then off it goes like a bat out of hell not missing a beat.
If you keep the revs up at a junction above 3500rpm and set off quick its fine but the clutch and my licence will suffer.
Now im sure it’s got to be a sensor that’s causing it but im not sure which.

The car its self has had a few mods and I know it needs a remap but it’s been fine with the mods so far
The mods so far are
2.5 engine conversions
Welbro 255 pump
Pro drive ecu
Ported headers and front pipe
Stainless Jap speed up pipe
Stainless Jap speed bell mouth down pipe
Full stainless single box ninja exhaust system
Panel filter
Resonator box remover and front ram pipe fitted
Dump valve
Hks boost controller set to 1 bar any thing over that and I hit fuel cut

Im thinking it might be either the coolant temp sensor or the lambda sensor both really on heat to work properly
But on other cars if the temp sensor goes they become hard to start in the morning and if it was the lambda it should show up on a gas analyser (my uncle owns an analyser in his garage and the lambda reading is fine)
If it was a coil pack I would imagine it would do it all through the rev range
If it was a crank sensor the engine wouldn’t fire
Throttle position sensor it would do it all the time not just cold

Has any one had this problem and if so what was causing it?
Please help

powerwrx

iTrader: (11)

i had a simlar problem with my my94 wrx, turned out to be coil packs.. when i took them out 2 of them had cracked and pieces fell off when i touched the ends.

car was fine after i replaced them with a new set

TURBOTRONICS

I would expect them to fail through the rev range but I will take them out and have a look
Thanks for the advice

jaytc2003

iTrader: (1)

coil packs in my experience tend to affect it later in the rev range rather than earlier. It does sound like lambada as it will be using that at those particular rev ranges. Anyway of you checking the voltages on the sensor?

TURBOTRONICS

Not as yet but I will be doing at weekend to see what readings im getting on all the sensors I can check
I could do with finding some kind of reference as to what they should be reading from cold and what they should be when up to temperature
I think I have a pin out diagram from the ecu some where

mit

iTrader: (10)

Wouldn't have thought the lambda would cause this,i ran mine with it dissconnected to diagnose a fault on my last scoob,made no difference t how it drove,it's only there for idle immision's anyway i think.
Any chance you have a leaking rear crank seal? Oil on the clutch could cause this.

Mit

TURBOTRONICS

It’s just had a new stage 2 clutch fitted along with a lightened and balanced flywheel
It’s more as if the ignition is being switched on and off rapidly
Any way IV just fitted a new lambda sensor tonight and I don’t want to tempt fait but it seems a lot better and the engine seems to sound different sort of more healthy
I will have to wait till morning to see if it has cleared up or if I have to move on to the next sensor