3vze Dying While Driving (7 Viewers)

[JunkCrzr89]

3vze in a 1990 4Runner with A/T has been dying while driving (i.e., engine stops running but electrical power remains). This has been increasing in frequency over the last couple of weeks. Up until yesterday, if the engine cut off, I could usually get it to restart without much issue other than longer than normal crank times. However, yesterday after it died while driving up a hill, the engine would crank and crank but would not start. I ended up flat towing it a few miles back home with my 100 series. I let it sit overnight and, as expected, it fired up without issue this morning. Drove it for 15-20 minutes and it died once again, but I was able to get it to start back up again after ~30 seconds of cranking.

Alternator is charging the battery fine (I'm getting 14V at the posts while engine is running) and the CEL is not on and there are no stored codes. Among potential culprits: I replaced the plugs and wires ~15k miles ago, the timing belt components ~40k miles ago, the VAFM ~30k miles ago, and replaced the fuel filter ~50k miles ago. I have a record from the previous owner that the fuel pump was replaced with an aftermarket unit 65k miles ago. The igniter and coil are likely original, and I have no record that the distributor was ever replaced.

I do have the FSM, which, for symptom "ENGINE SOMETIMES STALLS", the troubleshooting culprits are bad VAFM, bad EFI relay, or bad circuit opening relay. However, am I wrong in thinking that the symptoms may instead be early warning signs that the fuel pump is on its way out? Or, based on a few old threads on YotaTech describing similar symptoms, that the igniter and/or coil are dying?

 

[gnob]

check for spark and fuel when its in fail.
also with key on engine in fail, is the CEL on?

 

[mtnbiker4evr13]

I would also suspect fuel pump and/or coil. Have had the same symptoms IF the tank is known to otherwise be clean.

 

[JunkCrzr89]

with key on engine in fail, is the CEL on?

Yes, engine off after fail, key ON, the CEL lights up as normal with all the other indicator lights.

IF the tank is known to otherwise be clean.

I have no reason to believe the tank is gunky, but I suppose it could be after 33 years.

A part of me suspects the 33 yr-old igniter may be overheating and causing spark to cut out. To me, that seems like a logical explanation for why the engine will die after 20 min of driving (it gets hot), not start immediately afterwards (because still hot), but then start just fine after cooling off for 30 min.

 

[liveoak]

I mention this on a lot of 3.0 3.4 threads but both of those motors have fuel injector issues often, usually due to hot soak conditions from the exhaust manifold crossover design. They usually start causing hot start issues and random miss fire because they leak when they get hot. I'm not saying it's the issue but I would consider it along with the other possibilities.

 

[JunkCrzr89]

I mention this on a lot of 3.0 3.4 threads but both of those motors have fuel injector issues often, usually due to hot soak conditions from the exhaust manifold crossover design. They usually start causing hot start issues and random miss fire because they leak when they get hot. I'm not saying it's the issue but I would consider it along with the other possibilities.

Certainly possible since the engine fires up without issue when cold but won’t start after it cuts out when hot.

 

[JunkCrzr89]

I had a new spare coil laying around so I swapped it in. Truck ran fine for 20 minutes and then engine cut off again. The CEL was on so I checked it, got code 43. This is for the starter signal. So now I guess I’m looking at an ignition switch, wiring, or ECU problem? Seems odd that the STA signal would be causing the truck to shut off.

 

[gnob]

are you actually not getting spark when it's failing ?

if so check the pickups in the distributor.

 

[pappy]

are you actually not getting spark when it's failing ?

if so check the pickups in the distributor.

Ummm, I wonder if a cracked dizzy cap would cause this.

 

[gnob]

probably not unless water was involved.

i lost a distributor pickup on my 22RE once, gave very similar symptoms.

 

[JunkCrzr89]

with key on engine in fail, is the CEL on?

Now with the key ON, engine in fail, the CEL does not come on. However, if I let it sit for ~5 minutes, CEL will come on with key ON and it fires right up. I also have zero issue starting it cold in the mornings. Anecdotal, but more evidence is pointing to this being a heat-related electrical issue - something is getting hot and shutting off. Perhaps the EFI relay or VAFM? Time to get the multimeter out I suppose.

 

[gnob]

ok. so the easy thing is the efi relay.

Otherwise it sounds like you have a sensor failing pulling down the computer.
start unplugging main engine sensors until the light comes back.afm, tps, ect, o2 sensor.

 

[JunkCrzr89]

ok. so the easy thing is the efi relay.

Otherwise it sounds like you have a sensor failing pulling down the computer.
start unplugging main engine sensors until the light comes back.afm, tps, ect, o2 sensor.

Will do, thank you. I was editing my post above when you responded, so perhaps I provided some more useful information above. The fact that it starts fine when cold every morning, and after it dies it will start after cooling off for ~5 min, indicates to me that something is overheating.

 

[JunkCrzr89]

OK - Getting somewhere. Pulled the EFI fuse in the main fuse box (engine bay) and it has burnt up on one leg. Melted the plastic shroud of the fuse there.

So now the question is - what the hell caused that?

 

[JunkCrzr89]

Jesus…Swapped in a new fuse and it’s also already melting after 5 min of the truck running.

 

[gnob]

make sure your o2 wires aren't on the exhaust.
lot of stuff behind that fuse

 

[gnob]

do you have an ewd?

 

[JunkCrzr89]

do you have an ewd?

I have everything that was ever made available for this vehicle

Also, I picked up a cheap aftermarket EFI relay and swapped it in after the new fuse started melting. Fuse is no longer melting and truck is still running 40 minutes later. I’ll check the O2 sensor wiring now.

 

[gnob]

activate the old efi relay and check resistance across the load terminals.

 

[JunkCrzr89]

activate the old efi relay and check resistance across the load terminals.

I tested the old relay and it seems to be working fine at room temp on the bench. It is the original relay, so 33 years old at this point. I may pop it open and investigate.

Given the truck would start and run fine when cold every morning, and didn’t go into fail mode until after driving for 15-20 min, I wonder if the old relay developed fatigue cracks inside that would open as the relay heated up and then cause the relay to fail?