93 Altima stalling at random

you're speaking in the purely theoretical, not practical.

what you don't seem to understand is that experience /is/ diagnostics. if a particular problem presents itself repeatedly, and experience allows it to be identified accordingly, one would have to be autism afflicted to ignore the experience in favor of a flow chart.

i'm sorry dude, but as above, an oil pressure switch pressurizer attachment for my mity-vac is not available from any vendor that i know of. nor is a specialized test tool. and without either, the only other way to conveniently "test" such a unit is to compare the subject to one that's "known good" and observe differences in behavior. and that is a bona fide test procedure, even in a factory service manual.

in isolation no, but if, as you've been asked several times now, you'd bothered to d.a.g.s, you'll see that this exact issue is a common one on multiple posts, multiple forums. see above re "experience".

in theory, that is correct. but if you have any practical experience, particularly with something that's a regular point of failure on a particular vehicle, you'd have to have cognitive obsession issues to ignore it.

"based solely" is where you're making your mistake. and "non-skilled" is highly disingenuous for a newbie that clearly hasn't seen the high quality post history of the person they're criticizing.

on the contrary, it's the novice, poseur incompetent that /has/ to follow book. but only experience and ability to understand beyond the theoretical would allow you to come to terms with that.

Which was more or less my point.

But to willy-nilly suggest that an at best shade tree mechanic R&R a somewhat difficult to access and relativelty expensive OPS (if I correctly skimmed JB's suggested forum) without first confirming, or even so much as testing, is a ridiculous notion on its face.

As just one crystal clear example of a conspicuous reading comprehension issue, the "non-skilled reportage" comment could hardly have been more obviously directed at the inquiring *OP* (the only poster to have actually witnessed the supposed issue) who even required assistance locating the oil pressure switch. Having to yet again direct a return to my original remarks for clarification, suggests an inability or unwillingness to attentively follow a discussion. And resorting to a supercilious conclusion of inexperience on my part without any evidence whatsoever to support such a pretentious claim, bears all the earmarks of rationalization in combination with a wholly unjustified, haughty arrogance and accordingly renders my continuance of this conversation something substantially greater than simply pointless.

Well, pull the connector off the pressure sender. Does the car shut down?

Right, but the OP _did_ change the oil, and he reported that the oil did not look good.

If it happens again, diagnosis is possible. If it doesn't happen again, I'm inclined to believe it was a lack of proper lubrication.

True enough.

--scott

As would be clear to the critical reasoner, my suggestion was along the lines of an approach, not the actual cause of the fault. Per the OP's post to date, the issue is "resolved", without having replaced the OPS, providing a prima facie case for the "knowledgeable, experienced experts" having been wrong, although they COULD still turn out to be correct, but guessing and throwing parts at a problem ...

you need to re-read. steve w pointed out that the engine computer shuts down the fuel pump if the oil pressure is registered as insufficient. he also pointed out that low oil pressure [as is a symptom of old broken-down oil], is a known trigger. he further pointed out that if the switch was defective, and it's a known problem with this vehicle based on not just what he purports to be his experience, but a significant number of posts on this exact topic on other forums, the fuel cut-off would also trigger.

since the facts as reported by the op align with other data we've been able to check and verify, and you've /not/ been able to evidence anything contradicting what we've been told about this vehicle's operational logic, you saying it's "wrong" is not just wishful thinking or even denial, it's dishonest.

that's not true - this issue has been reported repeatedly on other forums.

excuse me? you're not prepared to acknowledge either simple information available to you on the web, not prepared to acknowledge that the kind of schoolbook testing you're advocating is impracticable, or that experience is relevant, but you're saying there's no "evidence"???

oh yes, there's plenty of pretension here all right. but it's not coming from the direction you're saying. quite the opposite.

if you spent less time with your nose in the thesaurus and more with it under the hood, you might be better able to have a rational conversation on this topic. there's even a possibility of your being able to authoritatively corroborate or deny the purported ecu logic. but as it is, you're simply sticking your head in the sand of denial and contributing nothing but entropy to the communal knowledge pool.

whoa there!!! you and your pesky logical thinking will ruin absolutely /all/ the, uh, "fun"...

First thing I thought of, but first the OP would have to know where it was. Anyway, nobody's answered the question if a '93 Altima has that shutdown circuitry. All I see is guessing and maybe myth about low oil pressure shutdown. I never heard of it in a car, and I can't find it on the net for any car. Not saying it doesn't exist on some cars. Didn't look real hard, but shouldn't have to. Anytime a car stalled everybody would be saying, "Did you check the oil pressure switch?" I'd be checking for that myself if my car stalled. But nobody's saying that. Except whoever first said it here and whoever thought it was a brilliant thing to suggest. It would be almost like "Sure you got gas?" or "Maybe your battery's dead."

Cheeses, what an absolutely unmitigated steaming pile of the most putrid imaginable variety of horseshit and pathetically feeble personal attacks, which, apparently unbeknownst to him, are counter productive and don't begin to bolster his case an iota.

Even he, who continues to repeatedly demonstrate proof positive his incapability to so much as manage to simply keep the undisputed facts straight, can't start to believe that he's actually kidding anyone able to distinguish a difference between self-evident, documentable, objective tenets and pretentious, supercilious, smarmy opinion.

I've been doing this work since the mid 60's, professionally since the early 70's for more than 15 years (having moved on to, albeit a now retired, engineering career at Caterpillar Tractor), have been irregularly lurking and posting here since the early 90's, and I'll more than gladly and easily positively compare and contrast my intelligence, education, training, experience and demeanor with that of his demonstrably risible ilk. And while directly laying that charge deviates from my norm and could arguably be deemed hypocritical on my part, it nonetheless remains a well earned and richly deserved slight.

Which could be only one of multiple ways of obviating the need for either testing the existing, or replacing with a known good, OPS.

We formerly commonly used Murphy Switch Gauges for both oil pressure and coolant temperature faults for shutdown on unattended industrial (mainly irrigation) engines when I was involved in that type of application in the 70's & 80's.

That's common for some applications - but not car engines. At least to my knowledge. But I always welcome education.

Using the O/P switch to shut down the vehicle is VERY common. It is pretty much the standard method used. Most even augment it with input from air bag or inertial switches that shut the pump off in the event of collision without engine damage so that broken high pressure lines don't cause fires. Usually it is a simple system with one switch used for the idiot light serving as the switch for the pump as well. Other use two switches, one for the light and a different one that uses a relay to power the pump. If you have a gauge then you also have a switch. Most of the switches trip on/off around 10-15 PSI. Some are down in the 5 PSI range though.

Not related to the original post but on most of the Fords made from around 1986 don't have an actual oil pressure gauge. The gauge in the dash is a fancy idiot light. When they redesigned the models and installed real gauges they got a LOT of complaints of the gauges moving based on engine rpm (just like they should!) and instead of trying to explain that as normal behavior they instead added a small resistor behind the dash and changed the sender to an idiot light ON/OFF unit. There are two really easy ways to tell which you have. One is to start the engine as you look at the gauge. The real pressure gauge will go way up to 60+ pounds for a few minutes as the oil warms up, then drop back to normal running pressure. It will also vary as you move the throttle. The other visual way is to look at the sending unit itself. The real gauge uses a sender that looks like a small can about 2" tall and smooth on the outside. The idiot light version uses a small switch that looks like a mushroom with a connector on top.

When you get into the newer vehicles you can monitor most of this stuff with a good scan tool. It's great to be able to see the actual working pressures without needing to tap into the system with a mechanical gauge. Plus with the real time data and freeze frame you can see what the ECM was doing when the code was set.

I know about the inertial switches, but never ran across an oil sender that would shut down the engine. But I've never pulled the wires off the sender to check, and haven't replaced one in decades. Thing is, you can read all over the place where relatively new cars lost their oil due to the pan plug coming out, or plain neglect - and the engine didn't shut down. It started smoking or clattering. So I don't think it's "VERY common" at all. How about naming some models? I STILL haven't seen one specific model car that has a low oil pressure shutdown.

That's one. And it probably really needed it too.

I had a '73 Chevy Vega that shut down when oil (or oil pressure) was low. Died on me going up a long grade. Put a quart in, started it & drove it home.

danielle steele, is that you? and would now be a bad time to point out that on usenet, purported credentials don't mean jack? all that matters is whether you can walk the walk. and so far, you're not evidencing even comprehension of that fact, let alone any such ability.