Still Randomly Stalling

I've posted about this problem before and I've never been able to get it fixed, but suddenly it's become critical because I'm relocating to place where I'm going to be driving on the freeway everyday. It's one thing to have your engine stall on a New Mexico back road, but it's an entirely different thing to have it stall on the freeway in Dallas during rush hour.


I have a 2001 Tacoma with 200,000+ miles on it. The engine will randomly die, even at highway speed; it will, with no warning, just stop.
I'll driving along and the RPMs will suddenly drop. As an example, I'll be at 2200 RPMs and it will suddenly drop to 1800 and it doesn't matter how much accelerator I apply, it will not go any faster. Once this happens, I have about 2 secs before the RPMs drop to 0 and the engine is simply dead. It's happened at 80mph on the freeway and it has happened driving through a residential area at 25 mph. It will go for a couple of months with no problems, and then out of the blue it'll happen. The last time it went for about a month and half with no problems and then it did it coming home from work two days in a row. After letting it sit for a few second, the engine will turn over and start but will only run for about 30 seconds before I hear a vacuum sound, then the engine sounds like it's out of fuel, despite having a full tank, and then it dies again. After I let it sit for about an hour, it will usually start up and continue running.

The battery is about a year old, a new fuel pump, fuel filter, and EGR were installed last Nov. It has a new MAF, new TPS, new computer, the throttle body has been cleaned and the Catalytic Converter has been removed.

Could this possibly be due to a bad Charcoal Canister?

One other thing; over the last few weeks, it has started missing and accelerating poorly, after it has been sitting all night or in a parking lot for several hours. After a few minutes it runs fine.

 

when was the last time spark plugs, and/or ignition coils were changed?

what engine do you have?

random engine dying almost sounds like a loose/broken wiring issue, or plugs/coils that are far past their 60k mile interval.

if you've changed all those parts so far, and the symptoms remain the same, i think it's safe to say that none of those parts are related to the root issue--most of those parts outside of the fuel pump, filter, and ecu, shouldn't cause a complete rev drop like that.

 

At least 2018. The truck was taken into Toyota and a complete overhaul was done, so I'm assuming the plugs and coils were changed then. I know they haven't been since then.

2.7L

I'm not doubting you with this question. If it's a loose/broken wiring issue, why does it start up and run after sitting for an hour or so? Same question the plugs and coils. Would they start up and run after stalling and sitting for a period of time? Would either or both of those things sound like the engine is out of fuel?

Yeah, they all seemed like long shots to me, except the ECU, I sure that saw going to fix it. I've done everything else that people have advised and it hasn't worked, and I can't think of anything else in the fuel/air system, so the charcoal canister was my last possibility. I keep coming back to the fuel system because it's strange to me that it will restart and then sounds like it's out of fuel.

I'm afraid to research how much changing the spark plugs and coils are going to cost me. I'm thinking somewhere between $500 to a grand with parts and labor?

 

i would agree about the fueling system. if you hadn't already stated you changed the fuel pump and filter, that would've been one of my first suspicions. though loose wiring at the fuel pump, or a bad fuel pump could still be a distant possibility.

i would also rule out the entire evap/emissions system. none of those systems would cause the vehicle to loose any part of the 'triangle of combustion' (fuel/air/spark), and stop running. problems with those systems would cause smoking, decreased mpg, and rough running, but not a failure to run.

(the rest of this is me working through each system, some might be relevant, some might not)

i feel confident in ruling out the fuel lines-- if they were cracked/loose, it should cause a hard-starting issue as well. really, any fueling issue ought to cause a consistent hard-starting issue.

in keeping with the fuel system idea, fuel goes from the tank, through the pump, through the filter, to lines up to the engine. at the engine, it enters the fuel rail, which feeds each injector, and at the end, is a pressure regulator that maintains a specific pressure, and anything over that pressure goes back to the tank to repeat the cycle.

any of those parts should cause other specific running or starting issues. the fuel regulator would be my next fuel-related suspicion, but it should be difficult to start, or have difficulty staying running. injectors are a common failure in older vehicles, but again, all of them wouldn't fail at once, and would instead cause rough running, or starting issues from the engine completing the 4-stroke cycle on less than 6 cylinders but more than 1.

because of all that, i want to rule out the fuel system-- it doesn't make sense that any of those components would cause sporadic half-then-full cuts in power, though the later difficulty starting unless it sits for some time could be known as vapor-locking. this still makes me suspicious of the fuel pressure regulator-- like it's getting hot and dumping all pressure for a until it cools down and the parts can mechanically reset.

i'd also rule out the air system. MAF would cause rough running because the ecu would need to be 'guessing' more on how much fuel to add to the engine to keep it running if the MAF was dirty or failing. but again, should never cause a running failure.


after that, is the entire electrical system, but again, if any part of the system had any issue, it should result in rough-running first. with the exception of maybe vehicle voltage-- the only thing that would cause an outright failure would be the battery wires loosening up, or the ecu loosing track of something.

to answer your question about the loose/broken wiring-- that's probably the hardest part, it's difficult to diagnose a problem that doesn't happen with repeatable circumstances. but a loss of voltage somewhere is one of the only ways i can come up with that would cause a running failure without getting the rough idle issues that a fueling, air, injector, or plug/coil issue would cause.

while i was working through the fuel system above, i was reminded of an issue GM vehicles had where they'd sporadically shut off while driving-- the official problem was learned that the ignition switch wasn't built to handle very large heavy key rings, and the weight of additional keys would cause the ignition switch to cut power to the engine. the fix was to remove the ignition key from the customers key rings so only the supplied vehicle key would be used in the ignition switch.

that's likely the simplest thing to test-- if the key cylinder is going bad, and you've got lots of keys, it could just be loosing contact to tell everything to stay running.

 

Is it setting any codes when it stalls/runs bad?

If it is that may give us direction.

If not then your gona need someone that knows what they are looking for, just throwing parts at it likely won't get you anywhere. Certainly would be a good one for Ivan at PHAD.

I'd want to be hooked up with a scope on the cam & crank sensors, coil control, and injector control wires, a scan tool monitoring vital PIDs, and a fuel pressure gauge connected then see what I lose when it stalls.

 

Is there a way for me to test the fuel pressure regulator other than just buying and installing a new one?

I do have quite a few keys on my keychain. The only way to find out is to take everything off my keychain and drive it until it stalls again.

 

No, the only code it throws is for the Catalytic Converter, which makes sense because I had the cat removed.

You would have to have everything hooked up at all times because there is no pattern to when it will stall. It may go 2 or 3 months without stalling and then it will stall 2 or 3 times in a week. There is no speed, RPMs. or timeframe to predict when it will stall. It is completely random

 

Yea random intermittent problems are the worst to diagnose and they are really frustratingfor bot a tech and the owner, without catching it in the act and testing while it's broken anything would just be a guess and anything tested when it isn't broken would likely test good.

That's why you really would want to be monitoring as many things as possible when it acts up.

Sometimes keeping notes of conditions when the event happens can help develop a pattern to be able to more easily replicate it, for example does it only happen on hot days, cold days, high humidity, low humidity, after a rain or damp weather, when the engine is cold or hot, etc...

 

the truck being a 2001, puts it in late ob2 territory, which means that it generally won't throw an associated code until it's been running rough for quite a while-- enough that the OP would likely already be questioning and scheduling a service appointment before the light triggers. obd2 alone is quite generous with it's fault tolerance.

there's really not. but you also should have other running issues with it as well, which is why i'm really leaning more towards an electrical fault than a mechanical fault. the regulator is basically just a flat disc with a spring behind it-- once fuel pressure goes high enough to overcome the spring pressure, it blows past and returns to the tank.

some of the more extreme troubleshooting guides i'm running across suspect that fuel is vaporizing within the fuel rail and screwing with the regulator and injectors, but this is a stock motor with no modifications-- meaning that toyota's prescribed equipment spacing would virtually eliminate that kind of issue..

instead of removing all of them, you could also try to put downward/sideways pressure on the ignition to try to replicate it. i know my old ranger, i could rotate the key backwards 1/16 turn and it would shut the motor down, but keep the interior accessories going.

the biggest thing here is to try to get it to do it consistently under any set of circumstances. from there, diagnosis is far easier.

i would also consider looking into disconnecting, inspecting, and re-connecting all associated electrical plugs for the ecu, and fuel pump, as those are the only two main components that would cause it to outright stop running without other rough-running issues. many of the connectors used are very easy to insert halfway and seem to work but fail to lock, which can present random shutdowns as the connector moves around (my back up camera failed to work after a deer strike-- they inserted the connectors together, but it didn't lock, so it didn't make connection). also inspect the wires within 12" of each connector for physical damage of any sort-- rodent damage is also a distant possibility.