Varying Idle speed.

[VNCalais98K]

Lately my car (auto 88 calais) has started Idling strangely.
When I start it, the idle (which usually sits around 650) will drop and rise sometimes actually stalling, and seems to be worse when its in park, rather than in gear.
I have new plugs and temp sensor, also have had TB cleaned out recently (september) so Im wondering what it could be?

Would a dodgy battery cause the car to idle strangely if it wasnt supplying enough current?
Would using too thick oil make a difference? (i wouldnt have thought, but someone mentioned the idea to me)
Could the ECU be shagged?

It tends to go away once i drive around a bit. but if i flog the car a bit it will come back and idle funny... possibly for different reasons?

[samuels]

Lately my car (auto 88 calais) has started Idling strangely.
When I start it, the idle (which usually sits around 650) will drop and rise sometimes actually stalling, and seems to be worse when its in park, rather than in gear.
I have new plugs and temp sensor, also have had TB cleaned out recently (september) so Im wondering what it could be?

Would a dodgy battery cause the car to idle strangely if it wasnt supplying enough current?
Would using too thick oil make a difference? (i wouldnt have thought, but someone mentioned the idea to me)
Could the ECU be shagged?

It tends to go away once i drive around a bit. but if i flog the car a bit it will come back and idle funny... possibly for different reasons?

it could be a number of things,so it's going to be a proccess of elimination.
in answer to a couple of your questions...yes it can happen,more so with battery,although the motor would stall,also you would not be able to re-start vehicle if battery was dicky as the alternator keeps it in a charged state while driving,one easy test for battery is checking it with a hydrometer....oil ...too thick can also cause rough idle,but sounds unlikely in your case,as it would have to be really thick oil.
i'm thinking along the lines of valves and fuel.one very easy test for your valves,is to hold a rag to your tail pipe with engine idling over,if the rag appears to be sucking in to tail pipe,this is a good indication that a valve(s) are going....as for fuel,check currents to injectors,check fuel filter,air filter,be even better if you can do a self diagnostic,can you perform one yourself?it could even be a leaking inlet manifold,the V6's are renowned for it,the gasket gets brittle and prone to cracking,i have seen a few go on the left hand side(passenger side)-as a lot of people think left hand side facing motor,which makes you obviously think...drivers side

[VNCalais98K]

....oil ...too thick can also cause rough idle,but sounds unlikely in your case,as it would have to be really thick oil.
i'm thinking along the lines of valves and fuel.one very easy test for your valves,is to hold a rag to your tail pipe with engine idling over,if the rag appears to be sucking in to tail pipe,this is a good indication that a valve(s) are going....as for fuel,check currents to injectors,check fuel filter,air filter,be even better if you can do a self diagnostic,can you perform one yourself?it could even be a leaking inlet manifold,the V6's are renowned for it,the gasket gets brittle and prone to cracking,i have seen a few go on the left hand side(passenger side)

Oil is thick.. its like 25-70 or something... and its been in for about 6000km now... due for a change.

Ill try the valve test today.

The manifold has only recently been replaced (november) so the gasket is fairly new.
Air filter (hi flow) only 3 months old.
I will check fuel filter... im going to service it next weekend, so it will be a good time to check these things.