Engine running abnormally - air leak or air-oil separator?

[ap1818]

My engine's been running abnormally recently. The issues that I've had intermittently are:

i) Rough idle fluctuating between 700-800 rpm. It's slightly rough most of the time. But, there has been a few occasions where it been more severe and it seems like anti-stall is kicking in.

ii) High idle fluctuating between 1,200-1,400 rpm. This has happened a couple of times when the engine was warm.

iii) On one occasion, whilst the car was warming up, the engine kept cutting out in-between traffic lights over a period of about 5 minutes or so. I kept having to restart the engine with the ignition and giving revs to continue. The engine cut out 7 or 8 times and then was ok, albeit with a slightly rough idle.

iv) On one occasion, in the rain, when starting the car, the engine had trouble staying on. It started fine, but just died straight away unless I gave it some revs. This happened 4 times but was fine after.

There's a hiss when the oil cap is undone whilst the engine is running. But there doesn't appear to be strong suction as the oil cap can be removed fairly easily. The only code that I've been able to read from the car with my basic OBDII scanner is P0507 – Idle air control system RPM higher than expected.

I don't know if there's an air leak, or whether the air-oil separator is on its way out or something else?

Has anyone has any similar issues? Any advice will be appreciated.

Thanks

 

[The Baron3]

Could be lots of things, get a code reader or and get the codes, his will help with your diagnosis, but it could be the following
MAF
Air leak
Cam Solonoid
Oxygen sensor

The list goes on, code reader should narrow this down

 

[Alex]

1st thing I'd do is clean your MAF. GT4 did a how-to on here if you search for it. After that it could be a numerous amount of things as stated above. I think possibly some of those issues aren't linked and totally separate.

 

[ap1818]

Thanks guys.

I've found the MAF cleaning DIY so will give that a go.