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Vehicle: 2001 Honda Civic with 220,000 miles. It runs and sounds perfect with no other issues besides the one described below.

Problem: When I start my car with a cold engine, the low oil pressure light remains illuminated until I increase the RPM above about 2000. If I never increase the RPM, the light never goes out. Once the light goes out, it stays out at any RPM and will not illuminate again until the next cold start.

Troubleshooting:
I replaced the oil (5W-20)
I replaced the oil filter
I replaced the oil pressure sensor
I have checked oil pressure with a handheld gauge: idle=13psi / 3000RPM = 52psi both on a warm engine. Values are higher on a cold engine, obviously.

Any ideas?

 
Rep Power: 519

So...what is the real oil pressure on the cold engine at idle RPM, when your light stays on?

If you disconnect the oil pressure switch and try it, does the light still come on?

 
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Unfortunately, I don't know the answer to this yet. Tomorrow morning, I will get the car back up off the ground and check the pressure on a cold engine at idle, but I need to buy an offset wrench to make the sensor removal/installation a little easier.

With the oil pressure switch disconnected, the light does not come on at all, not even when turning the key on with the engine off.

UPDATE: Leaving the house this morning, 15 minute drive, the problem was still the same, as stated above. Then, after being parked for 2 hours, I started the car again and the oil press light remained on at all RPMs and will no longer extinguish. The engine still sounds perfectly normal, but because the light will no longer extinguish, I shut her down, and will not drive it until I know for sure that I have proper pressure.

I suspect a failing oil pump, but really hope its something simpler. Is there anything else that could be causing this besides a failing pump?

 
Rep Power: 519

Is the engine sludged at all? Take the oil fill cap off, are the rocker arms covered in thick black tar?
A clogged sump pickup screen could cause low oil pressure when oil is cold and thicker (pump starvation). I have seen this more than once.

Put the real pressure gauge back on it first to verify if there is or isn't pressure when cold, and then decide where to go from there.



I see a spec of minimum 10 PSI @ idle hot, and minimum 50 PSI @ 3000 RPM, but I do not see a spec for the switch pressure.

Did you get a factory oil pressure switch? Aftermarket may not have the correct rating.

 
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The car is no longer at my house; its at my parents. I won't risk driving it home now. I will have to check that tomorrow when I recheck the oil pressure manually. That being said, when I changed the oil yesterday, everything looked normal inside, but I will inspect that much more closely tomorrow.

When I drained the oil yesterday, I ran all the oil through a magnet to pick up any possible metal shavings or contaminants, but that turned up nothing. The oil only had 800 miles on it, and it looked very clean.

That is exactly my intention for tomorrow morning.

Yes, I bought a factory switch from the dealer. Both my old switch and the new one produced the exact same indications.

 
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Oil pressure appears to be normal. I am getting good pressure at both idle and 3000 RPM while the low pressure light was illuminated. I was at a loss today, so I had the car towed to the dealer.

They checked the oil pressure, the oil pressure switch, voltage to the switch and electrical wiring to the switch. Everything checked out normal. By the time they finished all that, the light went out. I payed the $100 bill and picked up the car. I drove about 10 miles, the light stayed out until I parked, then I noticed the light was flickering dimly while the engine was idling around 750-800 RPM. The car was parked for 2 hours, then I started her back up, and the light was back on bright and steady at all RPMs. Praying that I had oil pressure, I drove the car 10 miles back to the dealer. About 2 miles into the drive, while on the freeway at about 60 MPH and 3000 RPM, the light went out. When I got to the dealer it was flickering dimly at idle again.

The engine runs and sounds perfectly normal throughout all of this. I am at a loss to explain it. The dealer still has the car.

 
Rep Power: 519

Tell them to leave it sit overnight so it WILL act up for them cold.
Then that they need to drive it 10 miles on the interstate so it will flicker at idle HOT, as you had it do.



I might connect with a "T" fitting so I can watch the pressure gauge and see the light if it comes on and see what pressure is at that moment. (The hose on my pressure gauge is long enough that I can tape it to the windshield so I can drive around with it hooked up.)

If the sending unit is new and factory part, I doubt it is lying.
I'm going to guess there are 2 issues happening:
1) pickup screen clogged, and
2) bearing wear from oil starvation. Maybe not enough to knock loudly yet, but enough to lose pressure hot.

These don't have hydraulic lifters like many other manufacturers' engines, so they don't get clattery when oil pressure drops. They don't make much extra noise until it's too late.

 
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Well, as it turns out, there is a pressure problem. It will cost me $300-$400 to have them pull the oil pan to check for contaminants or an obstruction at the screen. Then, if they don't find anything, it will cost another $1300 to change out the oil pump, at which time it would be silly not to do the timing belt (w/ water pump) change out for another $300.

After a long weekend trying to decide how much money I want to throw at this problem, I decided to trade the car in for a 2011 Civic EX. I just didn't want to take a chance that there may be engine damage and more expenses looming. It has been a great car for 12 years and 220,000 miles. I can't complain... and I love the new civic.

 
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$1300 for a new oil pump? hell if you have the pan off the the pump is simple to do at the same time. Wow. they are only $250 from Majestic.

Sorry to hear about your troubles, but enjoy the new ride!

 
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Yeah, that price was for parts and labor. They said between $1000 - $1300. I just didn't want to put that much into a car with $220,000 miles with possible engine damage. I'm not sure how long the pressure was low before the light came on. Believe me, it was a tough call; I really loved that car. From a low maintenance perspective, its the best car I've ever owned. That's why I bought another one.