club.liberty.asn.au

My 04 GT wagon auto has had a rough idle since I bought it. As far as I know it's completely stock, but it may have a non stock down pipe on it.

Rough feeling is intermittent ~2 sec rough, ~2 sec normal, and will waver back and fourth.

Only happens when stopped and in gear. If I back off the brake until the car is just about to move, the car will inch forward in the rough portion of the idle.

Doesn't happen every time, but does seem to happen once it's warmed up.

Took it to the mechanic who was probably just guessing but did an upper engine clean - which made no difference.

Any clues?

Mine was doing the same when I bought it,.. changed the oxygen sensor,... fixed

Yep, just been replaced recently.

Car is going in for its 150k service where they drain and replace all fluids basically so will see how it goes after that.

My cars the same, but has been tuned, so is running very rich to compensate for higher boost. don't think its tuned right though. Could be the answer to your problem if your cars been modified in the past.

https://au.bosch-automotive-shop.com/en ... 02-4-wires

Will this bosch oxygen sensor be s suitable replacement for the Front Sensor??

As i need to replace mine, because i also have the rough idle issue

Replace the sensor with the Subaru OEM sensor.

Also check for vacuum leaks

So issue still hasn't been resolved.

Has had 150k service which involved a second upper engine clean and idle reset.

Hasn't helped at all, if anything idle is slightly rougher. Has had O2 sensor replaced recently too.

Subaru mechanic blamed it on the non-stock dump pipe.

Had the same issue. Changed O2 sensor, had upper engine clean and injectors cleaned. Helped a bit but still didn't fix. Then checked for vacuum leaks and bingo, had quite a few! Replaced hoses, reset ecu and job done.

Problem solved.

Tuned by Kido on the weekend. 2 mins in, Matt identified vacuum hose was off. Problem solved. Runs like a dream now.