Oil pressure light coming on

I have a 1997 Tacoma 4x4 automatic with a 3.4 with 145,xxx miles . I have been struggling with a intermittent low oil pressure light flickering on at idle. But as soon at you give it any gas at all it immediately goes out. It also will only do it after 20+ mins of driving then when I come to a stop it’s there. So far I have replaced oil pressure sensor with oem Toyota, checked and cleaned the plug for the pressure sensor. I have also done two oil changes with filter and that will resolve the issue for about 800 miles then once the fresh oil brakes down the issue will come back. I did another oil change and it resolved it for another 800 miles but it just started coming back on. I have been running full synthetic 5w-30 per the manual. Any other suggestions on what this could be would be greatly appreciated thank you.

 

Welcome to TacomaWorld
Screen on oil pickup tube is clogged.
Time to pull the oil pan and clean out the sludge bucket.

 

Befor I did the last oil change I ran sea foam in the oil for about 30 mins to try to get rid of any sludge. If it was sludge why would the light not come on after doing a oil change?

 

Since you know how to remove/replace OEM sensor you might want to attach a gauge there, but I think since you replaced sensor pretty good bet low oil pressure is real. When I did my head gasket I went through a whole can of WD40 cleaning pistons and even after oil change I had flickering oil light at idle. It was very likely solvent in oil because when I sampled some oil into a clean container there was a light film on top. Additional oil change cleared it up.

I doubt you are getting gas or solvent in your oil but just thought I would relate my experience, have done quite a few HG's and this was first time I had an issue, it really threw me for a loop to say the least but have run an additional 5k miles so seems OK.

I was able to drain a pint or so of oil into a container by removing the drain plug and quickly putting it back. I think best to do this when oil is at least a bit warm and recently running otherwise solvents will stay on top. Let it sit for a while and look for any separation or a light film on top. I could blow on the film and it would move around so I knew it was a contaminant. If you have a strong magnet (like a stud finder magnet) you can run it along the bottom of container to see how much ferrous metal it attracts, I would see a smidgen of extremely fine particles like talcum powder.

Apparently a very small percentage of solvent will reduce oil viscosity quite a bit and I would only get the low oil pressure after driving at least 20 miles or so ands then of course only at idle.

Another trick I did was use a piece of solid electrical wire or similar and I bent it into a "L" shape and ran it around in the oil pan from the drain hole. No deposits whatsoever although does not eliminate screen blockage. I wonder if one of those inspection cameras would be able to see the screen?

 

Thank you for the info I will try that. Thinking I might add in more sea foam and drive with it in there for a hundred miles or so and then do a another oil change and maybe try 10w-40 instead of 5w-30. What oil are you running??

 

You've already run seafoam through the crank case correct? I think you're suggesting that 30 minutes of seafoam wasn't enough?

I'd just not screw around with guess what may or may not be in the system. Drop the pan and clean things up properly as @Black DOG Lila suggests.

I've always run M1 10w-30. I wouldn't jump to 40...

 

Yeah I switched to 10w-40 synthetic also, but just because I was so paranoid. I did about 30hrs of labor and $1000 in parts for the HG and then I get oil pressure light - very discouraging. However since then I let the clutch out in gear to slow the engine idle to 500 rpms or so and even then light does not come on so must be OK.

You probably know 3.4L have low oil pressure at idle, I think spec is 7psi and sensor lights at 5 psi. Believe it or not I read that owners manual says oil pressure light may flash on in certain situations but not steady at idle of course. So not much margin. Probably oil pressure under load is more important, you could get a cheap gauge and put it in the oil pressure sensor port. I did that after the last oil change (5W30) and it was Ok. About 7 psi idle and 30+ psi at 3000 rpm or whatever spec is. But a real mess because lousy oil press gauge leaked a bit. Be real careful on that port, don't install gauge or sensor tighter than it was originally as that bung can crack.

Sometimes engines have some metal debris in them from machining or casting that may get circulated and perhaps cause low oil pressure down the line as the engine wears even further. Pulling the oil pan on a 4WD is a PITA and may not find a problem. When I searched on this issue, I found one guy that was running Dino oil for 200k miles and his pickup did clog. Your mileage is real low for this problem to occur, are you original owner? Asking because perhaps previous owner did something stupid.

If I were you I would try 10W40 to see if that fixes it and then just drive it since diagnosing and repairing this (except for pickup tube) is difficult.

You could also have an oil analysis done to see if something is wearing but you have to run the oil for several thousand miles first.

 

You must get to the bottom of your low oil pressure. I have in the past encountered a clogged oil pickup screen so that is a possible.

Verify oil pressure with another oil gauge.

Other probables that show up as low oil pressure.
1. Countershaft bearings going out on you. I found out that my Driver's side countershaft bearing in the rear was starved and subsequently worthless. That countershaft bearing is the first bearing to starve. Its how the oil is pushed through the countershaft to the back. This can be your Achilles heel.
2. Worn crankshaft main and or journal bearings.

 

I think my next step will be to drop the oil pan What’s the process to replace the countershaft bearings? I’m not very familiar with that process or how involved it is

 

Simple things first.............. Mine did that and I replaced the oil sending switch and it fixed it.

 

I have already replaced the sensor first with a cheap orileys sensor and then a oem one. Didn’t fix the problem

 

Out of curiosity I googled if main crank bearings can be replaced w/o removing crank and looks like many cases they can but that is major surgery.