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Discussion Starter #1
I have an '89 Mercury Sable Wagon GS. I had the timing chain cover gasket replaced, because coolant was leaking aroung the cover.

3 days after the mechanic performed the gasket replacement, I noticed that the oil light on the dash cluster flickers when the vehicle's engine runs at idle speed. I had the mechanic look at it again, and he decided to replace the oil pressure switch and oil pump.

The flicking problem went away for one day, but came back the second day after the switch and pump replacement. The light does not come on or flicker when the vehicle is in motion.

I also notice that the engine makes ticking noises as well. I also live in NJ, and it has been generally below freezing temp for more than 3 weeks now. The oil I am using is Quaker State 5W-30 synthetic.
 

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Low oil I'd say.
 

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Old Ford Fan
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put a mechanical gage on it- hopefully your wiring just has a short somewhere- if its truly low pressure, only a couple things- bearings are worn, excessive clearance loosing pressure at low rpm(run heavier oil till you get it redone), or a bearing has spun- pressure will continue to drop lower and lower in a fairly short time until it self destructs.
Hopefully pressure is actually in spec, and if you look around front of motor, you might find the wire to the sending unit got pulled/pinched/somehow damaged from the recent service, and is getting an intermittent ground(most senders short to ground at low pressure to turn on the light). As engines tend to run a bit rougher at lower rpm that might explain a intermittent ground, or perhaps the harness runs near the throttle linkage. Good luck.
 

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Can't wait for Winton...
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As ford4v429 said, it’s likely to be a problem with the gauge or wiring.

Another possibility is the oil pump is worn. At idle the pressure is less than at higher revs, which shouldn’t activate the low-press light but if the pump is not working fully it may do so.
 

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Discussion Starter #6
As I said in my post, the oil pump was already replaced. I'll check for faulty and loose wiring. The funny thing is the oil light only flickers after cruising for 5+ miles on the highway and then going to a complete stop at the exit ramp.
 

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Maybe that oil is too thin for the wear on the car?? Idle speed too low??

Brent
 

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Discussion Starter #8
I decided to do the easiest check first - unclog sludge in the oil passages- rather than check the wiring. After adding the oil additive designed to break down sludge and running the engine for 3 minutes in idle mode, I drained the oil, removed the oil filter, and added new oil(Castrol 10W40 high mileage) and a new oil filter. I've ran the vehicle for 2 days(100 miles), and the oil light has not come on yet.
 
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