So after cleaning the oil/air separator and replacing the breather pipes and the valve, today I have a new(ish) issue. The car seems to be idling at around 900rpm. This is verified on both an OBD reader with live readings and of course the rev counter on the dash.

Having searched around the web I've seen one or two similar issues but not many - battery voltage is fine (13.8v at 900rpm idle). Rave does indeed say the car will increase idle under certain conditions but I don't think any of these apply. I've checked the MAF sensor by unplugging it - ECU reported the fault and I cleared it; it didn't come back. Live readings shows about 7g/s from the MAF which seems on the face of it to be reasonable. Long term and short term fuel trims look ok and I think the voltages from the lambdas are ok as well according the the numbers in rave.

Only possibilities I can think of are that maybe I've caused an air leak when replacing the PCV but I would have thought that would cause a lamda reading change and a subsequent change to the fuel trim. I'm not well up on the proper trim levels though. Also, one of the pipes I wanted to replace was not available (the very thin bypass pipe that runs directly from the PCV to the sump under the plastic manifold) so it has been left as is. It was looking like it needed replacing but not really gooey like the others.

Throttle shows 3% with my foot not on it and 900rpm idle. Anyone know if 3% open is the right number for the idle point?

It hunts ever so slightly but only by 10-20rpm maybe on the live reading.

Any ideas? I've said newish rather than new because in the past it has periodically done the same thing only to sort itself out after a restart of the ignition. I'm wondering if having sorted out the crankcase breather blockage it now needs to relearn the stored adaption parameters? There's a mention of this in Rave but the context is quite different really.

Also, as I was laying on top of the engine for most of the day I may have knocked something but I've replugged everything I can see.

I just disconnected the battery for 10 mins and it seems, touch wood, to be back to normal again. Out of curiosity I think I'll have a look at the throttle position % again.

I realize I'm talking to myself here but out of curiosity I checked the throttle position and it was showing 2% so the car was definitely deliberately opening the throttle for some reason. Curious. "Fixed" now anyway.

Interesting, thanks Ric...

Craig

interesting.

the throttle position you mention ... is it throttle pedal position, or throttle butterfly position ??

I'm more inclined to think its butterfly position as you said when it dropped to 2%, the idle dropped back down, so the extra 1% opening was giving you that extra rpm ( it always amazes me how little the opening has to be for the revs to rise quickly )

First thing that springs to my mind is the ECU would open the throttle and keep the revs up a bit for a while is for cold starts and when it goes through its warm up modes ... mine certainly keeps the revs up a little, then it'll drop down to normal once its been running for a bit.

If that were the case, then I'd be looking at inputs that measure the temp of the engine ... iirc there is one on the thermostat / pump area where you would be lying on top of the engine. its a twin sensor, i think one shows the temp for the dash guage , and the other for the ecu. maybe it sometimes thinks the engine is cold? and is holding it open?

maybe worth a disconnection of the plug and check the pins? no harm trying. V8 or else ...

My battery reset did the job, so at present I'm not considering it to be a fault. Time will tell though

It is indeed butterfly position that it is indicating and you are right that the additional opening was what was causing the revs. I sort of took that as a given. The curious bit for me was why the ECU thought it should be holding higher revs when no conditions appeared to exist that warranted that behaviour.

I guess I'll never know what exactly was going on with the limited diagnostics I have (an OBD reader and RAC). Being able to read all of the sensor values would surely have helped me understand it more and I have a feeling I'm on a trajectory that ultimately ends up with me buying a faultmate

i budgeted for one when I bought my FFRR. Its been good for when I've used it, and has probably saved itself in money now. ( Still think the software program is crappy though ) V8 or else ...