Help needed, I have an STI 5 with an occasional erratic idle problem which I am struggling to solve.

As the car happily idles away all of a sudden it is hunting like mad then after a bit returns to normal or just dies.

So far I have cleaned the air idle valve and this has not sorted it, then I have plugged the delta dash in. There are no fault codes shown but watching the figures on a data log when the car is struggling to idle she is over fuelling. You can smell it but watching the value on the O2 sensor and she shows 0.7ish when idling fine then 0.9 when struggling to idle.

Anyway I am struggling to figure it out wots wrong so please anyone any ideas?

Oh there is a very slight leak on the rear exhaust flange but surely this is not relative.

Thanks

Paul

 

Have never experienced it myself but failing MAF unit is often a culprit for that type of problem and I think they don't always show up as faulty until too late (engine failure !)

 

I did think MAF but when I watched the values on the delta dash the MAF output was the same when the car was running bad and good, still its an idea

Thanks

Paul