Thicker oil lower idle

I changed the generic 15/40 plant oil out yesterday in the capri, it has only done a few hours at idle and 50ish miles in 2 years and was primarily put in to flush out the old valvoline 20/50 racing oil.
I've put valvoline racing oil back in as that's what it's been run on since initial bedding in.
I've just started the car and it was uncharacteristically unwilling to catch, not slow to spin over but wouldn't start without a little throttle and then once running some 200rpm less at idle than normal. Typically the idle speed screw didn't work (to be investigated) can't be blocked as it's been in use only a few hours since I gas flowed it. So i richened up the mixture a touch, the idle stabilised but remained low and vulnerable to stalling at full lock and with electrical load.

I'm not worried as clearly the oil viscosity is the issue as oil pressure is also a little higher than before also but surprised that it had such an impact. Oh and the level is just above the minimum at the moment, so over filling isn't a factor.
A freinds brother runs an alpine and he had trouble when he used the same oil as the starter struggled to turn over his engine as the oil pump was causing such a load.

Hopefully the oil will thin with a few heat cycles.

Jon

 

I've been using Valvoline 20/50 racing oil for years in my 2.8i and not had any issues.

I'd suggest that it's something else affecting the low speed idle.

I find that mine is very sensitive to valve clearances and always needs the idle speed tweaked after I've adjusted the clearances at each service.. Ignition timing and fuel will also have a bearing obviously.

Jerry.

 

Ive used Valvoline 20/50 racing oil for many years when i did the top hat racing never had an issue with it ever

 

Same here, decades of it, no complaints.

 

Seems to have settled down now after a couple of heat cycles.
I had no idle speed adjustment and found I needed to open the butterfly just a touch on the stops as the idle bypass was flat out.

I wonder if the idle slow down is because my oil pump is an uprated item and makes the engine work just that bit harder when the oil is cold. Idle after all is the point at which the engine develops just enough power not to stall.

Jon

 

Quite possibly could have an effect on the idle. When I finished my engine rework a few months ago. I primed the oil system using a extension socket down through the distributor hole with my 1/2" electric drill.
My drill is only a cheapy but I have a lot of respect for it as it's nearly broken my wrist on a number of occasions with it's power. Priming the oil pump really loads it up big time and it doesn't take long to start heating the drill up.
My oil pump is standard with standard pressure as well, so I suspect with your up-rated oil pump will load up the engine even more.

I have found this with my engine as well. The standard idle bypass had little effect on my 3.5L engine and I always used to have to adjust the idle with the butterfly stop.