Most of the time my oil pressure is stable when hot, I can see this on my oil pressure gauge, but just lately the pressure fluctuates when at idle and the oil pressure warning light on the dash flickers on. The engine still idles fine and is not running hot & there is plenty of oil, oil pressure is fine when driving it's just when the car comes to rest and idles, anyone got any ideas why this is happening?

 

If your oil pressure light is coming on then you've got a problem (the light is switched at something like 5psi!), especially if it's showing fluctuations and low pressure on your gauge as well, ruling out a physical problem with the pressure switch.

Either you need a new oil pump or you've got a very low idle speed. Pump efficiency drops off very severely once you're below around 1000 rpm. An 800 rpm idle gives me a bar of oil pressure or just over which is fine, but if I let it idle any lower ( I can adjust mine with the Power FC) pressure drops again.

 

'tis normal for the oil pressure to drop at idle when engine has warmed up

 

The car happily idles at a steady 1000rpm once warm and higher when cold so I'm sure it's not idle related.
Is there any reason why this is only sometime yet most of the time it's fine? How easy is it to change the oil pump?
I have the factory fitted gauges, voltage,oil pressure and oil temp with the wiring for the oil pressure running along side the throttle cable before disappearing down in front of the inlet manifold and behind the alternator, I don't know where this wiring goes next?? Could it be the wire is piched or trapped?

 

Are they the factory fitted lamco gauges? My lamco oil pressure gauge has failed and they cost a fortune to replace. Tis a worry when your oil pressue gauge is playing up.

 

Yes they are the factory fitted lamco gauge. I'm worried because I've aleady had one bottom end go and with the warning light on the dash flashing as well I don't think it's the gauge. How are the gauge and warning light connected? Is it the same sender?

 

Not sure on factory fitted ones, but on my aftermarket gauge, I've got an adapter in the normal oil pressure switch point (behind alternator) which has two ports, one for the OEM pressure switch and one for the gauge sender. Presumably you've got a similar thing, as otherwise your dashboard oil pressure light wouldn't still be working.

The pressure switch is wired through a very short black wire back into the engine loom, so there's not a great deal that can go wrong with it. I'd trust what you're being told in this case - your gauge is showing fluctuations and your oil light which indicates VERY low pressure is lighting up occasionally. Your idle revs are relatively high so it's not down to that. The obvious thing is a genuine oil pressure problem.

 

Hi P1 , any worries m8 drop it down and I will slap my pressure testing kit on it...

 

Thanks Martin, looks like i'll be popping down to Plymouth soon then!