Yk could be a coil, it only dies once its heated up and running, but like I said it varies, could be highway speeds keeping it cool enough, or it warming up when it idles, but it blows and the engine dies after been running for 3 mins+ and let me grab an image

 

I see, yea that probably should get changed out, not exactly a simple fix though, looks like the nuts are pretty much gone, probably a good indicator the o2 sensor is ready to be replaced =) lol.

If I recall correctly, there should be a gasket between the o2 sensor and the exhaust, it looks like despite it being rigged up, it doesn't appear to be leaking much.

Another indirect route on checking the o2 sensor would be to do a plug check, pull a park plug out and see how it looks. Black is rich, white powder is lean, clean to light brown is just right.

If you can get it to act up again and not blow the fuse but die, you could take an old junk spark plug or have a spare with you, pop one off the engine and check for spark right after it died to see if you lost spark (then check the fuse since the blown fuse would cause no spark too). If you loose spark and the fuse stays good, might be able to point at the ignition coil for the fault, not sure how rare it is for them to fail shorted, possible, but haven't ran into that myself yet. Generally it's open (loose spark), or goes high resistance (weak or no spark). I have seen coils that failed in a shorted type of way, however it might have been other parts that caused it in those cases, signs on the coil was it overheated, melted/cracked etc, but that's on newer EFI engines with a bit newer style igniter, not sure if those older ones functioned the same way or not.

 

hey so I got it running and I was doing donuts and messing around jumping it while I could have some fun, I was taking it down our 5km driveway and when i turned a round and hit the bank to spin about she died, pulled the o2 plug off and still didn't start, she could been hot cuz I was rallying her pretty hard, but now I gotta look into that, I think a wire is getting hot and rubbing, not sure though

 

Another thing to do is test parts while it's hot. Multi meter and doing some ohming can tell a lot. Ignition coil and crank sensor would be the two primary things for getting hot then suddenly dying out like the ignition got turned off, that's assuming that fuse isn't blown this time.

 

yea, it wasn't a fuse this time, hasn't been since last year unfortunately, and I believe it must be a spark issue, I'm not sure if I mentioned it but it dies instantly, there's no sputtering like the fuel is cutting, it dies instantly, one second its on the next all the gauges are off except the speed, which is mechanical, so I'm gonna look into the coil, then I'm going to trace all the wires relating to the efi, distributor, and o2 sensor if that doesn't work, what really stumped me though, is the fact that blowing on the o2 sensor and tying new wire around it got it running for more than 5 hours and 10 starts, I'm confused to say at the least lol, by the way thanks for all the help I really appreciate someone else's feedback.

 

Could be as simple as something was shorted in the o2 sensor, not sure if it's a heated one or not though. You disturbed it, so things changed, could be wiring related, the actual sensor directly, but it's probably in that area for what was causing the fuse issue since it changed when you messed with that area.

On it loosing power, that's a whole different thing, instead of loosing spark like the ignition is turned off, loosing all the gauge power and such IS loosing ignition lol. Anything related to the ignition system and turning on the main ignition relay would be suspect including the ignition switch. Sounds like you have quite a wiring headache with that one lol. Could be as simple as a relay going bad, bad connection, bad ignition switch loosing connection (wiggling the you should see things get effected by it though). Also very possible you have more than one issue going on both related to wiring.

 

I'm being told it's likely ignition then, because yea everything shuts off in an instant every gauge just drops and not slowly flips over instantly, I'm gonna check the ignition and see if something was tampered with there, the truck had a killswitch installed into it by a mechanic here who sounds like he's an idiot, there a really good chance he mightve messed with a cable in the fuse box? I can send pics later, it's a little messy underneath

 

 

I'd follow that red wire lol, clearly not stock.

 

Had the exact same issue with my 85 22R. One time the truck even stalled while driving 65 on the freeway. Luckily I was already driving in the slow lane and I just had to coast over to the shoulder.

Anyway, I suspected it was the negative battery cable connection. It was somewhat loose and didn't make a tight connection on the battery terminal. Sometimes I'd go over a pothole or bump and the truck would stall for a second or two, but then return to normal.

In any case I replaced the connection and now it fits tightly over the terminal and the problem is solved. So you may want to look at your battery connections. Make sure everything is snug, remove any corrosion, replace as needed.

 

the thing is, is it doesnt start again, once its off your not getting it running, it takes a day or so and u try it again and it starts, so something is getting hot and failing or bumper and failing, I've looked through almost all of it and there's nothing super unusual but I'll fix it coming up soon here when I have the time. Thanks! I'll check it out, that'd be great if that's the issue. Lol

 

Bad ground connection can act like that sometimes. Take all ground points under the hood apart and even just tightening it back up could fix the issue short term. If it does, then clean up the threads on the bolt, the face of the bolt that rubs the ring terminal, and of course the actual ring terminal. There is no reason to grind off the paint on the body etc where it bolts to, the threads are the ground point, the face of the bolt "eats" into the ring terminal and makes the connection through it to the threads.

I suspect it's more likely to be a coil based part like crank sensor, ignition coil etc. Since it takes a long time to restart, you should have a lot of time to ohm the related parts out to find the one that's bad (while it's actually not working). You could also check for powers at the injectors, ignition coil, igniter, and you should get a check engine light on with the key just to on to show the computer has power and is alive. I don't recall how the air flow meter is wired up, but the fuel pump relay is controlled by it after it starts, so there's probably 2 power feeds, one might be 5v for the actual air measuring side.

 

I',ve had my 1990 4Runner 30+ years, it has a 5sp manual. During that time, there was ONCE I went to a fast food place and parked & shut it off. When I came out, the 4Runner turned over, starter & battey fine. Would not start for nothing.
I had to call AAA. They took it to their shop. They had it 2 weeks. They changed quite a few things involving the fuel system. I really complained. Remember these are OBD1. The problem turned out to be the knock sensor (under the manifold) was not
permitting the ECU to activate ignition or the fuel pump. I don't know which. Since that time, I am aware that all the ECUs on toyota cars & trucks had microfarad capacitors. There was a period or a known problem that capacitors in the ECU might leak.
There are ECU refurbish outfits that can replace those caps. There might be 7-10 of them in there. I still have all my orig caps on my 34 year old ECU. I have even bought a spare ECU from a salvage 4runner that is maybe 1 year newer, a 6cyl and 5 speed tranny manual. One day, I'm going to inspect the inside of that ECU., and compare with my backup. You can get ECUs salvage for $45 to $80 DLLs from ebay. But the PN should be close to the label of your original. A cap ties into my knock sensor. I did not throw away my bad knock sensor. It might have been something bad in the ECU , or marginally bad.

 

Basically all ECU's have capacitors in them, from my understanding their life span is around 20 years, so realistically a lot of computers should be failing because of caps. I don't repair ECU's but I've seen enough come up in searches of mine that it seems like it's the most common issue with them. All of the electrolytic capacitors can and will leak at some point, they are sort of like a AA battery, the bottom rubber seal goes bad over time or internally they fail and build up pressure and either the rubber leaks out or the scored end of the "can" bulges out and splits. If neither of those 2 happen, then it explodes like a firecracker. Here's an example of one, you can see the bulging on both ends before it goes.


General rule of thumb, if you're aware of the cap issue, and your computer has the orig caps, it should be rebuilt (caps replaced) before they actually fail. This saves the board from being damaged, and capacitors don't have to physically fail to still be bad. They can effect sensor readings, power supply, voltages, timings, etc, so having new correct capacitors installed should make the vehicle run as if it was new given that there's no other issues.

OBD1 vs OBD2 doesn't mean a whole lot, a good mechanic doesn't "need" to read codes, it's just handy to have a reference for what direction to go with things, sometimes the codes can be misleading and hinder the diag work.

Knock sensor signals to the computer engine knock and it pulls ignition timing (retards the timing), even with extreme knock I'm pretty sure the startup cycle ignores knock sensors, at least that's based on a 93 camry I've worked on that had a really bad rod knock. Would start and run normal for a couple seconds then have so little power it couldn't even move the car. I don't think it would prevent the engine from starting, but with bad caps a lot of really strange stuff can happen.

ECU does not control the fuel pump on a 1990 4Runner 2.4L, while cranking, the starter relay that goes to the starter solenoid also powers the COR (circuit opening relay) which is effectively a fuel pump relay. Once it's running the air flow meter takes over with a physical switch (it meters air with a physical flap and has a contact inside for fuel pump control). On newer vehicles it's typical for the engine computer to control the fuel pump, like the 93 camry from the example before does have that type of setup.

I work with ECU's effectively daily, a "close" part number doesn't mean anything, just 1 digit off can be for a completely different ignition system design and won't even work. They *should* be an exact match so you know 100% it interchanges, big time for a daily driver. In the context for the ones I work with, it's for demo derby cars, so they don't care if the ac system is a different design from one car to another, that whole system gets stripped out when they go smash the cars up. Close years doesn't help either with out checking the pinout, I messed up on that before with a 97 T100 auto trans computer in a 98 T100 manual, connectors matched up so figured it should be good, same engine and such. Well the igniter was signaled to turn on solid, so the 3 coils were effectively hot wired to power until they failed and then they took out the igniter. After replacing those and repinning the engine harness to match the computer, it was one of the best running 5vz manual trucks I've ever owned (I think the auto tune is better, but I only used that computer because manual ones were $500+ and already had this one on hand). If I remember right close to 50 wires were pinned differently.

My guess is your computer has bad caps making the circuits react in a way that isn't expected. I'd say if you have the spare funds, buy a spare computer with a perfectly matching part number, then send that one out to be rebuilt, then install it in your 4runner. The budget way is to slap the used computer in and hope it doesn't have cap issues which it likely will have at some point due to age.

While on the cap topic, replacing them is a pretty easy process, just have to be somewhat detailed oriented (match capacities up right, clean the board well, etc), and it could be a DIY type of repair that should cost under $50. Capacitors in bulk are something like $0.10-$0.50 each, larger ones sometimes run more.

I wonder what fuel system related items the shop replaced on the 4Runner. A simple pressure test would show if the fuel system is getting the correct fuel pressure (fuel pump and regulator are working and the lines, and filter aren't completely plugged), if it's close enough the engine should normally run. That would also confirm fuel pump control is working or not. That would rule out pretty much everything except the actual injectors which is extremely rare for all 4 to go bad at the exact same time so unlikely root cause. A NOID light would show them if there's injector pulse which is the 2nd test I'd do on a crank no start vehicle after checking for spark. Spark but no Pulse I'd be looking at power related items to make sure everything is getting the power it needs, then the focus would shift to computer and crank sensor, don't even need to read a code for that one on something older like that. Anything newer in the mid to late 90's I'd be checking for an engine immobilizer (security) since that's the common way it prevents the engine from running.