low oil pressure on idle

[dlb]

i searched this on the forum but came up with 91 pages of results and nothing i saw addressed what i am experiencing. btw, this is on the all-trac--i feel like a turd asking an all-trac question here but it's not specific to the car and can apply to tercels as well so i figured it's not totally out of line.

in the last week i noticed the oil light flickering on idle sometimes. it seems to happen once the engine has warmed up and the idle RPM drop to about 800-900 but that's about as consistent as it gets. sometimes it doesn't happen at all, but when it does it flickers very lightly. it does not stay lit.

when i got the car several weeks ago, i noticed the PO had overfilled the oil but it didn't seem to be too much so i left it. after a few weeks and about 800 km of driving, the oil light started flickering on idle so i re-checked the oil. it was actually quite overfilled (by almost 1 liter) so i drained the extra liter because i know that too much oil can decrease oil pressure. that hasn't stopped the oil light from flickering on idle. the car has high km on it (325,000 km = 200,000 miles), it has had oil changes regularly at every 5000 km its whole life, the oil in there now is still perfectly clean and golden, and there are no weird sounds or anything abnormal performance-wise with the engine. it drives excellently.

my worst fear is that the crank bearings are worn but the history of the engine being so well cared for and performing so well for makes me think that is unlikely. what are other possible causes of low oil pressure? i've heard faulty oil filters can cause it. i also wonder if the oil pressure sender is faulty. i looked in the tercel manual for pertinent info and to check oil pressure, it says to remove the OPS, hook up an oil pressure gauge, get the engine warm and check the pressure at idle and at 3000 RPM. is an oil pressure gauge a specialized tool? i've never used one before so i'm not sure if i should go to the parts store and ask for one.

thanks in advance, gang.

[Petros]

DO NOT DRIVE IT UNTIL THIS IS RESOLVED. I have had this same problem are various cars/trucks because of different reasons.

Go to an auto parts store and by an aftermarket oil pressure gauge, they are inexpensive (less than $20 with install kit). You can get the kind for mounting on the dash and just use it for the test, but if you can find a place to mount you can install it and watch it as you drive it. Even a cheap brand will work for the test, but if you want to mount it on your dash permanently, I would get a better quality one. Cheap ones can develop leaks and drip oil inside the car. I like the mechanical gauges, not only do they cost less but are direct reading with few parts to malfunction.

The oil sender could be bad, and oil pressure is okay.

The oil sender wire could be chaffed and grounding with vibrations, and the oil pressure is okay.

The oil pump or the internal pressure relief valve, could be faulty, worn or marginal, or the bearings are worn out. If this is the case you will damage the engine if you continue to drive it. When I ignored this once on a Toyota truck, I had to replace the whole engine when it threw a rod and seized the engine, it was not rebuild able at all,.

So you MUST verify if the engine has oil pressure before you do anything else.

Typically a bad pressure relief valve means it will have low oil pressure at all driving conditions and all rpms, with it only coming up slightly when you rev the engine, and perhaps slightly higher on cold start-up when the engine oil is cold. The oil pump and pressure relief valve are identical on your 4afe engine as on the 3a and 4a engine, a worn out pump or stuck pressure relief valve will not generate enough oil pressure to lubricate properly.

Also with a worn pump or worn bearings, you will typically see high oil pressures at cold start-up, and at higher rpms, but after the oil has warmed up, the idle pressure drops to 8 or 10 psi, where the idiot light starts to flicker on. So you have to run the engine until it gets good and hot to know if the pump or bearings are any good. I have also seen a pressure relief valve stuck part way open, (it had grit caught in it), and it would give very low pressure at low rpm (idle).

My current daily driver, the cream colored '84, has the oil light flickering on and off sometimes, and I have it completely disconnected. I have a separate pressure gauge right now, so with the sender removed and the wire disconnected, my light still comes on. So it has to be a chaffed wire that is occasionally grounding the light. IF that is the case with you too, your engine is safe, but finding the damaged wire is a time consuming PIA (and why I have not done it yet, I will likely just remove the bulb).

Lucky for you, if it is the oil pump or bearings, that car it is fairly easy to drop the pan, replace the oil pump, and/or the rod bearings. It does not matter, btw, that it had the oil changed regularly, if any grit got in the engine oil, or if it was ever ran dry of oil by mistake (sometimes even the Quick oil change outfits can do this by accident), the bearing and oil pump will be wasted and need to be replaced.

Good luck.

[larry mcgrath]

dbl what did you think about the acceleration of the v20 b/t leaving petros'es house ? back to your problem you might check to see if you have gass in the oil (leaking fuel pump diaphram,pumping raw fuel into crank case ,high oil level) peter is right buy a mechinical oil press gague it WILL pin point the problem. Possible too light of engine oil in crank case. Good luck Larry

[dlb]

larry, i think you can guess how i feel about the acceleration. i was actually thinking as i followed you that you have the perfect sleeper car--i don't think anyone will expect to see that kind of performance out of one of these cars!

very well. i will remove the OPS, measure the threads, get an appropriate fitting, thread it in, attach a mechanical gauge via a vacuum hose, and keep my fingers crossed.

a few more questions: what are some appropriate OP readings? on the 3A, the FSM says 4.3 PSI at idle and 36-71 PSI at 3000 RPM. when i spoke with a parts guy today while looking for a gauge, he said the general rule is 10 PSI per 1000 RPM but peter, you mention dropping to 8 or 10 PSI as the point that idiot light starts to flicker. i don't have a FSM for the all-trac yet (it's in the mail) so i'm not sure how to interpret the readings i will get.

also, when you mention the pressure relief valve being stuck open due to grit, i assume that the only way to remedy that would be to remove the oil pump so you can get to relief valve and clean the grit out by hand. is that right?

[Petros]

you can clean out the pressure releif valve after you drop the oil pan, you have to remove a clip and the spring and plunger should fall out. If it is stuck you have to use compressed air to blow it out. But at that point you might as well remove the front pulley are pull the pump. That will allow you to remove the rear cover and inspect the pump gears, and properly clean out the relief valve. If the valve is jammed up you might consider replacing the oil pump.

There is no way for fuel to get into your crank case with this engine, what larry wrote is true for the 3a and 4a engines with carbs, your 4afe is fuel injected and has a separate high pressure fuel pump in the gas tank, not on the side of the head. Checking for the correct weight oil is not a bad idea however.

I have a manual for the all-trac, I will check tonight and give you oil pressure information. I seem to remember the oil light sender turns the oil light on at 7 psi. It should run about 25-30 psi after warm up, and idle above about 10 or 12b if I recall. the higher the better.

[dlb]

where'd you get your all-trac manual, peter? i just bought one off of ebay. it was about $50. i'll likely scan it all and get the guys at alltracwagon.net to post it. the tercel FSM (while by no means perfect) has been a great resource and i can't stand such a thing not being readily available to a community of enthusiasts.

speaking of correct oil weight, i read an article online about the topic. it said that the lower a weight # is, the thinner the oil, and that the first # is the cold oil weight while the second is the warm oil weight. so 10w-30 oil is thinner (10) until it warms and thickens (30). the oil is thinner when cold to help lubricate the engine on start up. but if that's the case, why is oil pressure an issue only when the oil has warmed and supposedly thickened? it's always seemed like oil is thinner when warm to me. anyone want to clarify this?

[Petros]

you missunderstand. I forget the temps, but that means at room temp it has the weight of 10 wt oil at room temp, and at operating temp (like 210 deg F), it has the weight of 30 wt oil at 210 deg F. 30 wt oil at 210 is still thinner than 10 wt at room temp.

[dlb]

hmmmm. i'll keep reading.

did you find the specs on the all-trac oil pressures? i'd really appreciate those. i hope to check the pressures tomorrow, if all goes well.

[GLet71]

Found this on the alltrac site:

By the book/spec, the oil pressure at idle should be 4.3 psi and up. Nope, it's not a typo, i meant it - 4.3psi and up.

At 3000rpms it should be 36-71psi.

http://www.alltrac.net/phpBB2/viewtopic ... 30&start=0

Take a look, maybe they're referring to a different auto

[GLet71]

Oh crap, that's for a Celica awd, sorry.

[dlb]

turned out you were right anyway, glet. 4.3 psi seems to be toyota's minimal OP reading of choice. the pain though is that most gauges don't start reading until 10 psi, including the most accurate one i could find. regardless, i pressed on and spent, oh, 3 weeks searching for the correct adapter. turned out to be a 1/8" x 28 BSPT male to 1/8" NPT female adapter was what i needed. once i had that info i had no trouble finding one but boy, it sure took a while to find that out.

with the correct adapter, i finally hooked the OP gauge up a few days ago and after warming up to operating temperature, the OP stayed steady at 22 PSI. i was very happy. but get this: when i first hooked the gauge up, i ran the car for 30 seconds and then shut it off to check for oil leaks in the gauge line as per the instructions. i looked and it was good but i could hear dripping from somewhere. i looked underneath and saw coolant pissing out! i had previously noticed that the radiator was a little ugly but it didn't look too bad. i guess it had been marginal to start with, and 3 weeks of sitting allowed it to rot past the marginal point and it finally gave up when i started the car. it was wild that it was a leak but not the leak i was expecting to see and yet ANOTHER hassle to deal with, but also really lucky that it happened at home in the driveway. ordered a new rad and the OPS, put them in yesterday and took the car for a few test drives. drove about 120 kms of mainly highway driving and got the oil good and hot. i'm please to say that all is well so far but i'm keeping an eye on the oil light for now, just in case.

[Jarf]

DLB - for the record, true pressure sending units are notoriously unreliable, whenever I run into that syndrome I just replace the sender and go from there.
It isn't just Toyo, it is across the board. When I was at Jag they actually brought out a "fix" that involved installing an idiot light sender ( with a resister to make the gauge read at the mid-point). They just got tired of customer complaining about the "low" reading (hot engine, idling).

I would still keep a close eye on the oil level.
The fact that your engine seems to make oil is a physical impossibility.
While Petros is right that you have a FP in the tank there are still other ways you can get fuel into your crankcase.
Leaking fuel injectors comes to mind and even more suspect would be cold start injector, as well as excessive FUEL pressure.
I have seen blown fuel regulators that allow the line pressure to run too high, causing over-fuelling/ crankcase contamination.

Just something to watch out for, if you really are having fuel in the crankcase, that WILL wipe out the engine.
For the record, I would be more worried about the head, fuel contaminated oil is a very poor lubricator and there is nothing worse than wiping out the
cam "bearings" as they are not replaceable, just get yourself a new head.
At least crank and rod bearings can be changed.
Coolant contamination is a very visible thing but fuel contamination is harder to spot AND aside from it's poor lubricating abilities, it WILL cause low pressure as well.
BB

[dlb]

thanks for the ideas, jarf. i smelled and looked closely at the oil i drained and it seemed fine but i will check again when i do an oil change in the week or so. all is still well so far, engine runs really strong.

The fact that your engine seems to make oil is a physical impossibility.

sorry, i guess i wasn't clear about that. the oil was overfilled when i first checked it but i didn't realize just how much so. it wasn't until i re-checked it later that i realized how bad it was.

here's my guess as to what happened. judging by the quality of work the PO did on the car--lousy wiring on the fog lights, aftermarket speakers, and stereo, removing a rear windshield wiper rather than replacing the broken wiper motor, that kind of stuff--i don't think he was much of a car guy. so i imagine that the oil light started flickering sometimes and he just kept adding oil, hoping that would increase the oil pressure, not realizing it would have the opposite effect. when that didn't help, i imagine he figured the engine was on its last legs and decided to sell the car for substantially cheaper than they usually go for to get rid of it before it blew. i'll never know but judging from his work that i've seen and talking with him about cars, i imagine it's pretty likely.

[Jarf]

Okay, now I understand.
I had the impression it was a little over, then it was a lot over, my mistake.

You are most likely correct in your assumption.
The PO sounds like some of my previous customers.
"That damned oil light keeps coming on, I put more oil in it and it didn't change a thing".

[celtglen]

I ran for hundreds if not thousands of miles throughout the Rockies to work and home for two years (sleet, rain BIG snow) not knowing my OPS wire was unplugged. But as I am OCD about oil and how the car handles I never thought much of replacing it.

Not until this year did it begin to seep oil, I had some $$ to put in to the car and replaced the switch--the one I bought is WITH the "light" if that makes a difference..maybe it is the wrong one? The wire connection to it was so crappy that I stripped it and put on a new female connector and plugged it in.

When I turned on the car it blew the gauges fuse in my kick panel! Replaced that and it blew it again. So I left the wire off and got the blinking idiot light on my dash--,mind you it is not connected to anything...so I wrapped a piece of electrical tape over the wire's end and over the light in my dash.

This was MONTHS ago and I continue to watch the oil level.

Any of you guys heard of the wire that connects to the OPS blowing a fuse?