Engine Hunting and Very Rich Cold Start

[ephesiangts]

Hey guys,

Thought I might see what people think.
I have an 04 GT Liberty Wagon Auto. Mods: STi ECU(Factory), K&N Air Filter, HiTech Catback 2.5".
I have an Idle issue where it Hunts every no and then, doesnt do it all the time, just some times.
Subaru have done all the usual things, upper engine cleaner, reset idle etc but still have no idea.

Also at cold start, it is so rich on start, smells horribly like paint fumes. But settles like a normal cold start.

I have had 02 sensors replaced.

As I side note, I can only get 540km MAX out of my tank on BP Ultimate on a highway trip if I nurse it.

Also, just wondering how people rate the exceleration and take off in GT Libs. I find it very sluggish unless thrown into ssport mode.

Any ideas?

[parso_rex]

Checked the MAF sensor ? it sounds very much like that to me as you've already changed the O2's

[ephesiangts]

Checked the MAF sensor ? it sounds very much like that to me as you've already changed the O2's

Do we know the approx opperating range on these so I can check with MM to see if its stuffed?

[cruisn]

Mine did that exact same thing and it was the o2 sensor behind the turbo, but as this has already been replaced.....

Unscrew the afm from the airbox and spray with some contact cleaner.

[Ben]

Needs a proper tune to get rid of the pig rich cold starts. The STi tunes and 2.0T in general are quite bad and ping from factory. Just the extra fuel burnt on start up and the carbon fouling everything would add up to the cost of a good tune, plus you get more powar.

Nobody has properly got to the bottom of the actual cause of the hunting besides 'clean the injectors' 'replace the o2 sensor' 'clean the afm' blah, some got rid of it, a lot are in the same position a few months later! Subaru Japan now have better o2 sensors as the old ones failed often (Phat GT is getting them in atm).

'youngy69' seems to know more about actually diagnosing the issues and fixing them than most, he's in Sydney and with Subaru (Lindfield?), so if you're based there I'd go and see him.

[ephesiangts]

Mine did that exact same thing and it was the o2 sensor behind the turbo, but as this has already been replaced.....

Unscrew the afm from the airbox and spray with some contact cleaner.

ok will do.

PS: did ur 02 sensor throw the engine light though? Mine did, thats how i know it was cactus!

[Q]

Mine did that exact same thing and it was the o2 sensor behind the turbo, but as this has already been replaced.....

Unscrew the afm from the airbox and spray with some contact cleaner.

I replaced a faulty 02 sensor (from Subaru $$) and the new one turned out to be intermittently faulty as well so don't think because you replaced it that it's working correctly. Took a while to track that problem down! Really does sound like the o2 sensor is the issue....and a tune would help it no end!

[ephesiangts]

theres also 2 02 sensors isn't there? one behind turbo and one behind Cat?

I'll get them checked out.

Can u buy these 02 sensors aftermarket?

[Ben]

theres also 2 02 sensors isn't there? one behind turbo and one behind Cat?

I'll get them checked out.

Can u buy these 02 sensors aftermarket?

The one in the dump pipe behind the turbo, read my post above. Phat GT has them on the way.

[cruisn]

ok will do.

PS: did ur 02 sensor throw the engine light though? Mine did, thats how i know it was cactus!

Mine didnt throw a CEL. Did you change both o2 sensors? The one behind the dump is the culprit for this issue.

[ephesiangts]

So spoke to Subaru dealer that replaced sensor. They only replaced the front turbo 02 sensor. not the rear one. So might need the rear replaced. And then ill get a tune done.
Brother follwed me back in his B4 from picking car up from panel beater after getting front resprayed because of stone chips, got sti lip put back on. And he said there was massive amounts of rich exhaust fumes pouring out back when it was cold. went away after a while. So its obviously super rich on cold start. A tune is immanant. Any sugestions where to go as im from Bathurst and would be going to Sydney for it.