Erratic And Random Idle Hunting

[pikesrelaybus]

This seems a little wierd. Iveco 3.0ltr, 160ps HDi engine, sometimes, quite often actually, it "hunts" at tickover just after starting. Rev's fine, drives fine, doesn't seem to be linked to engine temperature. Just hunts, it's not even enough to see the rev counter needle go up and down, probably only plus/minus 50-100 rpm but it's enough to make me wonder what else is going to happen... So far this engine @ 75k miles has done fine, only needing a throttle body and a new belt tensioner.. Hmm, any thoughts?

[pikesrelaybus]

Update... We're at 92k miles now, still hunts at tickover. I've also had a few P0235 (turbo boost sensor errors). If I understand things right the ECU monitos the manifold pressure, engine speed and throttle position a determines if all is well as they all interact with each other. With this slight revving I guess sometimes it detects a infridgment of these levels and lobs the light on. The ECU only illuminate the engine management light when it's detected the same error a few times. I've also noticed that now and again it says I've no oil but clearly there is and at the right level. I'm beginning to thing the sensors are failing or becoming inaccurate. If the turbo boost sensor is the one that fits on the top of the manifold, I've had that one out before and it was covered in soot and garbage. However, I'm not so sure. I think that may be a airflow temperature sensor as the little bead thermister was within the probes protective plastic cage, which, before I cleaned it was full of soot and rubbish. Still, I hope that someone may have an idea...

[paul.h]

I have read elsewhere that turbo boost errors could be indicated if there is a leak in the small bore vacuum hoses around the various sensors, so you could have a look for any splits in these at the sensors.