I have a 90 EX. This has been going on for awhile. Basically, when I am doing anything besides driving straight ahead on smooth ground, I get a regularly-blinking (not flickering or solid) oil light and have to key off and key on to clear it. Then I can go on until I hit another bump or whatever else.

Yesterday I checked immediately after having to fight off the oil light several times while driving to work and the oil level was at the FULL mark (meaning it was probably over-full actually since oil would still be up in the head.). I saw it come on and then go off on its own while making a hard turn, while accelerating bumpily uphill, and a couple of times while going over a potholed road. I figured it had to be low. Then I look at the dipstick and it's FULL.

I take a bumpy/hilly route to work and get the blinking oil light almost every day. I go home on a smoother route and I have never seen the oil light on that route.

I have changed out the sender (with parts store not HONDA) and fiddled with the wire end and bundle with my wife watching the light and the light never came on, but I also removed the wire entirely and the light didn't come on. I guess there would have to be an intermittent grounding of that wire for it to cause a false positive to the ECU. Don't see how that could be happening due to motion unless there was a broken wire or bad solder joint.

I removed the sender and tested with a manual gauge and I get 15-20 at idle (warm/hot motor) and 60-65 at 3000 rpm very steady. So I don't think it is a pump or pressure relief valve problem but I have no idea what happens when I'm driving.

At this point all I can think of is that the pump is occasionally sucking air maybe through a loose pickup (I rebuilt the motor about 5K miles ago). Also I will try a new HONDA sender in case I have two bad senders. Next time I change the oil I will drop the pan and take a look at the pickup but I wonder if anyone else had thoughts on this.

Other stuff that doesn't fit into this story.
1. One time I got off the interstate after 2 hours of driving and when the car idled down the flickering/solid oil light came on. Level was full when I checked the next morning. Haven't seen that since, not even after the drive back when I stopped for gas.

2. I swear that sometimes I will check the oil and the level will be low and later I will check and it will be higher, and then low again later. There is no "milkshake" nor lost coolant from the rad. Could I have a drain-back issue from the head somewhere? I don't think there is any sludge because the head was hot tanked and rebuilt and the oil pan was not sludgy when I had it off.

I remember there being a round valve of some kind that went a hole between the block and head that seemed like an oil metering device of some kind. I wonder if I screwed something up in the placement of that or put it in backwards? If all my oil is up top and not draining back to the pan that would explain a lot. But not why I get a light and then immediately read full on the dipstick. The "oil control orifice" can be found here: http://www.hondaautomotiveparts.com/...LOCK+-+OIL+PAN

I know the F22A6 has a windage tray on the pan and wonder if I would benefit from an oil pan swap with my F22A4 if that is possible.

 

As you have deduced the oil light comes on when the sending unit circuit is grounded. With the engine off the switch is closed. With oil pressure the switch opens.

The steady flashing oil light means something specific. It means the ECM saw a momentary loss of oil pressure for more than .5 seconds. Once oil pressure is restored the ECU recieves the signal from the sending unit and commands the light to flash. This is to make the driver aware of a momentary loss of oil pressure ( since the light would be no longer illuminated from the pressure loss ).

I recently replaced my sending unit with a Honda factory replacement ( $5.00 ) due to the light coming on at warm idle.

Your symptom suggests a loose part. Maybe the pickup tube, as you mentioned, since the engine was rebuilt. It is also possible that since the engine was removed and rebuilt, there is an intermittent short in the harness somewhere that only presents itself when the vehicle is shaken, such as when running over a pothole.

 

Unplug the sending unit and drive over the same area of road that causes the symptom. If the light still comes on, the problem obviously electrical.

 

That won't work because I unplugged the sender and the light didn't light at all because it seems the wire has to be grounded by the sender to light.

 

Ok, maybe this is my culprit after all. I put the original HONDA sender back in today and will see if it makes any difference but will definitely get a new one when I have a chance.

I actually rebuilt the whole thing without removing the shortblock, believe it or not. There is enough room to get it done and the main bearings can be replaced without removing the crankshaft using a trick or two. Unfortunately I had one cylinder a little out of round according to my measurements and I think I earned myself a piston slap at low idle as a result. I can live with it but I need to resolve this oil problem or at least convince myself it's not a pressure loss, but I don't see how it could be much else because of its predictability and association with certain physical events.

Even though the engine was not removed there still certainly could be an intermittent short in the harness. I have had problems with the O2 sensor plug which makes the harness suspect.

 

This would allow you to remove the oil pressure sender input from the circuit. If the light came on it was because somewhere along the harness the wire was grounding. Know what I'm sayin?

 

I know, you can slip the bearings around the crankshaft. I've done it myself. If it were possible, you could hook up the pressure gauge and drive the car. Observe the pressure gauge while going over bumps to see if the engine is actually losing pressure or not. Could be tricky, but given the scenario needed to recreate the symptom, it may be your only choice besides replacing parts. I'd start with a new factory sender. They are cheap.

 

Ah, I get it now. Sometimes it takes me a few cycles. I would like to try that but for some reason the thought of driving around with the sender unplugged makes me verry nervous

 

I will definitely get a new sender ASAP. I may be able to slip the mechanical gauge hose through at the edge of the hood. It is pretty long. I'll try that out but first I need to get an adapter for the correct threads for the gauge. NPT thread adapter for the gauge leaks.

 

Well, that !$%$@ oil light is busted! I got a mechanical gauge in and I'm going down the highway, with about 40-50 steady psi on the gauge, hit a bump and BLINK BLINK BLINK. Key off, key on, and this happened 2 more times when I sped up fast or hit bumps just like whenever I drive to work. I am not surprised since I had to repair wires for the O2 sensor already. Guess I am going to pull an engine harness out of the junkyard unless someone knows a better place to get one.

Though there may be some truth to the light. After getting everything warmed up and going for a drive on the interstate, I have about 5-10psi at idle (I think idle is set correctly, about 500rpm), 15psi at 1000rpm and 35-40psi at 3000rpm. That seems to be marginal, what do you think? I am running 5w-30 dino for now, wonder if it would improve with synthetic.

 

The oil pressure switch closes at 4.3 psi.

When you hit a bump and the oil light started bliking, were you observing the gauge? Or, did you use the oil pressure switch hole to connect the gauge? Just wondering if the vehicle actually lost pressure or not.

 

Good info, thanks. By the way, also for the sake of info, the adapter required to hook up the oil pressure gauge was a 1/8 NPT female to 1/8 BSPT male which I found online for about $8 shipped. I used a few turns of teflon tape on both sets of threads so it wouldn't drip.

I had the gauge connected and routed up past my hood latch to where I could watch it while I was driving. The Harbor Freight gauge is nice because it has a looong hose on it. It was making solid PSI varying directly with engine RPM, and there was not even the slightest anomaly visible on the gauge when the oil light started blinking as usual, except this time it was disconnected, so it gave itself away.

 

your motor needs more oil.

 

If the oil light started blinking with the connector unplugged the problem is either an electrical short or a malfunction in the gauge.

 

Can't be, it was above the top mark on the dipstick when I checked it cold.

 

Yes, I think it's a bad engine harness since like I said, I had to repair O2 sensor wires before. My main question is if I should be worried about the PSI numbers I am seeing on the gauge when the oil is all warmed up.

 

I wouldn't be. If you fix the electrical problem and the light never comes on again, happy trails!

 

For the hell of it I pulled the ICU apart and checked capacitor ESR, they were good. Put it back together and haven't seen an oil light since. Could re-seating the connectors have been all it needed? Doesn't make much sense since it's looking for a ground, not an open, so I don't know how bumping the ICU would blink the light. Guess I'll pretend it's fixed for now unless I see the light again.