Erratic idle and smell.

[FatRS]

My Ph2 172 has developed an erratic idle, not just from cold. It's done it for a total of about 40 minutes and still there when I turned off.
It has revved all the way up to 3000 revs at points and keeps the revs up when changing gear also.
There is also a smell that can be smelt at he engine bay and comes in to the cabin. It's not strong and hard to describe.
Last week I had the Cambelt, aux belt, water pump and Dephaser changed by a senior Renault tech at my work (Renault main franchise service agent).
Could the problem be related to this? Not using the correct tools? (I assumed they have them being dealer) or as I saw using the search facility could it likely be the inlet manifold? Would this need to be removed to do this work?
Sorry for all the questions but I'm not exactly...should we say technically minded.
Thanks in advance for your advice guys. Over to you....

 

[MicKPM]

I'd call the place that did your belts and ask them to check it over. It sounds like an air leak to me.

 

[FatRS]

Could it be anything to do with me cleaning the air filter?

 

[hilldawg172]

Definitely won't be air filter mate the cleaner the better.

 

[FatRS]

Just tried it again now and it all appears to be normal. Standard rough sounding idle due to solid mounts but steady at about 800 rpm. The smell is still there. I'm taking it back in tomorrow to look at it again. Any more ideas as to the cause?

 

[MicKPM]

I've known the new aux-belts to smell funny for a while after being replaced. Its a very strange smell; not burning rubber but rubber like.

 

[FatRS]

Yeah. Really odd smell to describe. Not a burning smell. Not a oily smell. Just a "heat" smell. So the thought is the smell could be normal... Fingers crossed it is.
Thanks for feedback.

 

[MicKPM]

It doesn't happen on every belt change but I've deffo had it on a few before.

 

[Jamie]

My car has developed a funny smell, deffo around the aux belt, but it hasn't been changed in 2.5 years.

Took it to the garage, they looked at it and said they can't see anything wrong, but it was deffo coming from the aux belt area. They couldn't see any damage per se.

 

[Jamie]

From a bit more of a search it's water pump or alternator.

No issues with it overheating yet and still charging at 14v's ish - so give it a day and some more investigation and hopefully I'll know which one it is.

Seems a common issue/problem.

 

[FatRS]

The smell has gone from mine and the idle has settled down however it is still "lumpy" until warm and it seemed to take ages to get to temp the other night. I don't drive it much so unsure if longer than normal. Seemed to be 20 mins at stand still.