when the car is cold it hesitate really bad til it warms up then it only does it a bit.any suggestions

 

MAF

 

new maf and o2 fitted

 

Lamdba sensor warming up...they all do that sir.
If you disconnect the lambda is wil be nice a smooth as it will use the ECU base fuel map rather then trying to achieve stoich using the Lambda sensor.

 

coolant sensor

 

Why instead of stabbing in the dark has nobody reccomended he take it to his dealer....lol...

 

....take it to your dealer

 

I'm not stabbing in the dark...just try it. It's gotta be cheaper then £70 per hour a dealer would charge.

When the engine/lambda sensor is cold it sends false readings to the ECU, so the fuel mix causes it to surge as it rocks from rich to lean. Once the sensor is up to temp it should be alot better.

As mentioned, if you disconnect it you will find cold running alot smoother. It will run open loop from the base fuel map and won't even flag a CEL. Beleive me I've done it several times.

 

Is this safe to do?

I am a firm believer of "it's there for a reason".

 

Scott is right. I suggested MAF as you say it does it when warm also. Mine was doing this due to a failing MAF. replaced it and it runs sweet as although the 'pulsing' hesitiation is there when cold. MY99 UK turbo.

What mods do you have if any?

Did you do an ECU reset after fitting the MAF?

 

They're all a bit lumpy when cold (as Scott T says) It shouldn't be doing it when warm though. Did you replace the lambda before of after the failing maf? A failing MAf will quite often take a lambda sensor with it apparently.

If not, take it to a Subaru specialist. No-where near £70 ph, many will do a diagnostic for the price of a beer or two!

Ns04

 

The Lamdba is only there to get the car through emissions testing.
It will run fine without it, but probably wouldn't quite pass an emissions test.

My MY00 UK on a OE ECUsurges alot when cold and marginally on light throttle when warm. It doesn't with an apexi though

 

Thanks for clearing that up

.....Hmmm Apexi....