HELP! Engine Shutting off Randomly.

[Sotovo]

*Disclaimer - I know there is a million things this could be, and without physically seeing the vehicle we can't actually come to a conclusion about what's happening, I am simply posting this to see if anyone has had a similar situation, thank you in advance for not just telling me to take it to a shop.

I bought my 1999 Limited 4Runner about 6 months ago, 168k miles and a clean bill of health with excellent maintenance records. I have out about 20K on the truck now. Randomly, about 5 times since I've bought the truck, the engine will shut off. 2 times just cruising on the highway, and 3 times after I've revved up the engine to redline (twice just to feel the acceleration and once when my uncle asked me to Rev it up in Park so he could hear how it sounded)

All 5 times I just pulled over, turned the key off, and then turned the truck right back on and it drove perfectly like just like normal.

Not sure if this is electrical (spark plugs and wires) OR
fuel related (injectors, 02 sensors or something like that.

So I turn to you fellow Yota peeps. Any experience with this happening? Let me hear your questions, comments, concerns, thoughts or theories?

 

[Konkordmusk]

Is your check engine light on?

 

[LittleCaesar]

Check to see if the fuel filter has been changed.

If not, then possibly look into changing it but if I were to bet that the Astros were going to win their division this year, I'd say it is the fuel pump. Any hard cranking? You may need to check the fuel pressure.

 

[Konkordmusk]

Check to see if the fuel filter has been changed.

If not, then possibly look into changing it but if I were to bet that the Astros were going to win their division this year, I'd say it is the fuel pump. Any hard cranking? You may need to check the fuel pressure.

Also, this.
You know, it could also be the keyswitch. Something internal could be messed up such that it may cut ignition power to the engine when certain conditions are met.

 

[SpidermanGeek]

I've had a similar issue and did some research on this. The most likely culprits aside from the Fuel Filter would be a dirty MAF, TB and IAC valve. And/or the Front O2 sensor.

Nobody seems to have found "The Cure" for this problem, but doing the combination listed above seems to have fixed the issue for most people.

I had the same symptoms as depicted in other threads as well. Get on the throttle (WOT) end get the RPMS hit readline to merge onto the highway and as soon as I let off the gas to take the offramp.. truck stalls. Pull over, wait about 10 seconds and it fires right back up.

I recently cleaned the MAF and tried to reproduce the issue, but without success. Meaning that the MAF cleaning might have done the trick.. but I'm still skeptical as it could be a number of other things preventing it from happening again (summer fuel, warmer ambient temps).

 

[SpidermanGeek]

http://www.toyota-4runner.org/3rd-gen-t4rs/125944-engine-dies-after-wot.html

engine dies after WOT - YotaTech Forums

 

[Sotovo]

I've had a similar issue and did some research on this. The most likely culprits aside from the Fuel Filter would be a dirty MAF, TB and IAC valve. And/or the Front O2 sensor.

Nobody seems to have found "The Cure" for this problem, but doing the combination listed above seems to have fixed the issue for most people.

I had the same symptoms as depicted in other threads as well. Get on the throttle (WOT) end get the RPMS hit readline to merge onto the highway and as soon as I let off the gas to take the offramp.. truck stalls. Pull over, wait about 10 seconds and it fires right back up.

I recently cleaned the MAF and tried to reproduce the issue, but without success. Meaning that the MAF cleaning might have done the trick.. but I'm still skeptical as it could be a number of other things preventing it from happening again (summer fuel, warmer ambient temps).

Thank you so much! Finally someone who gets what's going on. I think all those are great Ideas and will add those to the list to check. Can you spell out what those initials are for ? I am new to 4runners and not a vehicle expert so what are the others besides MAF? (i know mass air flow )

 

[Sotovo]

Also, this.
You know, it could also be the keyswitch. Something internal could be messed up such that it may cut ignition power to the engine when certain conditions are met.

Thank you so much for the reply! I had someone tell me that it could've been something with the key-something, but yes the KeySwitch. Thank you!

 

[Sotovo]

Is your check engine light on?

No, no check engine lights or any codes being thrown. when the car is plugged into a OBD reader it shows everything is running @ %110

 

[SpidermanGeek]

Thank you so much! Finally someone who gets what's going on. I think all those are great Ideas and will add those to the list to check. Can you spell out what those initials are for ? I am new to 4runners and not a vehicle expert so what are the others besides MAF? (i know mass air flow )

MAF = Mass Air Flow
TB = Throttle Body
IAC = Intake Air Control
O2 Sensor = Oxygen Sensor

WOT = Wide Open Throttle

 

[Sotovo]

MAF = Mass Air Flow
TB = Throttle Body
IAC = Intake Air Control
O2 Sensor = Oxygen Sensor

WOT = Wide Open Throttle

Thanks so much. You've been a great help. I am taking the truck in the morning to the Toyota Specialist to get new Spark Plugs and Wires, Fuel Filter, Oil Change, and he's going to look at all the major engine grounds to make sure it's grounded properly.

On my own, (so he doesnt charge me)
I'll clean the MAF sensor, TB w/ SeaFoam
and Run some seafoam through the gas tank and crank case

I'll update you as things are done!

 

[gamefreakgc]

Thanks so much. You've been a great help. I am taking the truck in the morning to the Toyota Specialist to get new Spark Plugs and Wires, Fuel Filter, Oil Change, and he's going to look at all the major engine grounds to make sure it's grounded properly.

On my own, (so he doesnt charge me)
I'll clean the MAF sensor, TB w/ SeaFoam
and Run some seafoam through the gas tank and crank case

I'll update you as things are done!

P.S. you can replace the spark plugs and wires pretty easy on your own if you want to save some money. You will just need a set of deep sockets (I think it's 16mm for our spark plugs), 12 in extender, and a socket wrench. But by no means do you have to do it, especially if time's a factor.

If you do though, we can help with what parts to buy.

 

[jeremyc74]

Since this seems to be tied to going WOT for a lot of people, I suspect it might be the throttle position sensor, and it may just be dirty. It may be that there's gunk built up on the section of the rheostat that the wipers only hit during WOT, and it's giving the ECU bad readings and causing it to freak out and shut down.

The only way I could see a dirty fuel filter causing something like this is if it's so clogged up that it's causing the fuel pump to trip a circuit breaker that automatically resets, and I think the fuel pump on these trucks is fused so that would rule that out.

There's no way it's the plugs or wires. You'd get missing on individual cylinders, not a random shutdown. The MAF is a possibility, but typically when those start going bad they cause serious drivability issues.

 

[SpidermanGeek]

I agree with you that the most likely cause is a sensor going berzerk after WOT and the ECM reacting in a panick to it, trying to give the right fuel/air mixture and it goes wonky enough that it shuts down the engine. One theory is that the engine actually drowns on fuel when you suddenly cut the air off from lifting off the throttle suddenly. I dunno.

In my case, I also just ran through a fuel tank with Dura-Lube system cleaner in. It might have helped clean whatever fuel sensor might have been gummed up.

 

[jeremyc74]

I agree with you that the most likely cause is a sensor going berzerk after WOT and the ECM reacting in a panick to it, trying to give the right fuel/air mixture and it goes wonky enough that it shuts down the engine. One theory is that the engine actually drowns on fuel when you suddenly cut the air off from lifting off the throttle suddenly. I dunno.

In my case, I also just ran through a fuel tank with Dura-Lube system cleaner in. It might have helped clean whatever fuel sensor might have been gummed up.

There really aren't any fuel sensors though. The fuel system on these trucks is pretty straightforward.

The pump runs anytime the engine is running, at a constant speed. The regulator bypasses fuel back to the tank to maintain a constant fuel pressure on the rail. There's a vacuum bias on the regulator that will cause it to increase fuel pressure under WOT. The filter is between the pump and the regulator, so even as the filter gets dirty the fuel rail still sees the same pressure. If it's really bad it could certainly cause some issues in upper RPMs, but it still wouldn't cause it to die and then start up and run normally again.

There's also the possibility that it's something in the actual ignition circuit, but that wouldn't really have anything to do with going WOT. Old Jeeps were notorious for having bad ignition switches that would cause them to die when you hit bumps, but I'd be surprised if that's what's going on here.


If it's being flooded on throttle closure that would lend even more weight to the TPS being the culprit.

 

[Sotovo]

There really aren't any fuel sensors though. The fuel system on these trucks is pretty straightforward.

The pump runs anytime the engine is running, at a constant speed. The regulator bypasses fuel back to the tank to maintain a constant fuel pressure on the rail. There's a vacuum bias on the regulator that will cause it to increase fuel pressure under WOT. The filter is between the pump and the regulator, so even as the filter gets dirty the fuel rail still sees the same pressure. If it's really bad it could certainly cause some issues in upper RPMs, but it still wouldn't cause it to die and then start up and run normally again.

There's also the possibility that it's something in the actual ignition circuit, but that wouldn't really have anything to do with going WOT. Old Jeeps were notorious for having bad ignition switches that would cause them to die when you hit bumps, but I'd be surprised if that's what's going on here.


If it's being flooded on throttle closure that would lend even more weight to the TPS being the culprit.

Wow Great info. What you're saying makes a lot of sense.. I am just going to start ruling stuff out with the old trial and error method. I treated everything with seafoam today, gas tank, crank case, and went straight into the throttle body. It's already driving better. My goal is just to get it as clean as possible and update all the parts I can to see what's actually causing the problem. I am going to look into it being the TPS and see about cleaning or replacing it. That sounds like the most viable thing so far.

 

[Sotovo]

P.S. you can replace the spark plugs and wires pretty easy on your own if you want to save some money. You will just need a set of deep sockets (I think it's 16mm for our spark plugs), 12 in extender, and a socket wrench. But by no means do you have to do it, especially if time's a factor.

If you do though, we can help with what parts to buy.

I would love to change the plugs and wires on my own. Please let me know what the best to use are. I'll look up some write ups to see procedural things.

-also, we have the same color 4Runner

 

[SpidermanGeek]

Please let me know what the best to use are.

The answer to 99% of any "What Brand of Part should I use?" question when it comes to 4Runners is Genuine Toyota OEM Parts for best results.

 

[Sotovo]

P.S. you can replace the spark plugs and wires pretty easy on your own if you want to save some money. You will just need a set of deep sockets (I think it's 16mm for our spark plugs), 12 in extender, and a socket wrench. But by no means do you have to do it, especially if time's a factor.

If you do though, we can help with what parts to buy.

The answer to 99% of any "What Brand of Part should I use?" question when it comes to 4Runners is Genuine Toyota OEM Parts for best results.

That makes sense. I dropped the truck off at the shop this morning, they're changing the oil and fuel filter, and he also said that he would clean the TPS for free. So fingers crossed

 

[Sotovo]

Check to see if the fuel filter has been changed.

If not, then possibly look into changing it but if I were to bet that the Astros were going to win their division this year, I'd say it is the fuel pump. Any hard cranking? You may need to check the fuel pressure.

Yes, it does hesitate to start sometimes, but it always does start.