2006 4Runner Engine Shutting Off While Driving

[Mikasa67]

I need some help from you wrench heads out there. My 2006 Sport V8 4Runner has developed a very aggravating issue that I can't get to the bottom of.

History:
This issue started on the day I completed a suspension lift and was test driving my runner, could be total coincidence or not? Didn't make any changes other than springs/struts etc. normal lift components.

Problem:
As I'm driving along the engine seems to shut off or loose total power then come back on-line. Usually it only happens for a second or two, but has killed the engine if running at a low RPM. It's not throwing a code that can be read and when I drive it around reading it with a diagnostic tool on my laptop it sees nothing strange other than the RPM dropping off. On the instrument cluster during the power loss I get a very fast "AT/Oil Temp" flash, then the "Check Engine" light, then the thing goes back to running correctly and they are gone until it does it again. It does not seem to be engine speed related, it happens at high or low RPMs. It does although seem to be worse when accelerating hard.

What I have done to diagnose so far:

1. Thought it was acting fuel related so I put a pressure gauge on the fuel rail, it reads a constant 42psi even when the engine is shutting down and having the issue.

2. Seemed to be acting like it may have water in the tank, I have now ran two tanks of fuel through it treating each one with STP fuel conditioner. It says it will help with water, but who knows at this point.

3. I read somewhere that a faulty key switch can act like this, so I connected a multimeter to the key switch to monitor the voltage. Never saw a major blink. It stayed within the 14v range the whole time and was tested on the acc1 and acc2 outputs.

4. Spoke with a Toyota mechanic and he thought that I could have pinched a line in the fuel or evap systems, but I can't find anything damaged or pinched.

The "AT/Oil Temp" light flash throws me, is there a safety mechanism that shuts the truck down if the fluid is too hot? There is no indication of a AT leak or issue, it still shifts OK, or at least as good as it ever did.

Any ideas what to look at next?

Thanks for any help,

 

[bamma]

If you hadn't checked the fuel rail I'd think it was a fuel pump for sure. A fuel filter could do that too.

You don't happen to have an aftermarket alarm with a starter bypass/disable by chance? Do you have another key you can try?

 

[m85476585]

That's weird. At high engine speeds, as long as the transmission is in gear, it should be able to drive the engine even without fuel. Most modern cars will cut fuel to the engine when you are costing. Not sure if 4runners do that. Using the throttle cancels fuel cutoff, obviously.

 

[chompster4runner]

Fuel relay?

 

[Mikasa67]

If you hadn't checked the fuel rail I'd think it was a fuel pump for sure. A fuel filter could do that too.

You don't happen to have an aftermarket alarm with a starter bypass/disable by chance? Do you have another key you can try?

Good point, totally forgot to include that information. I do have a remote starter and thought that could be the problem. Took it back to the installer to see if there was any possibility that unit could be failing and act this way. They told me there were no wires cut to install that system, but only tapped in and he highly doubted it could be the problem. They showed me where to test from the key switch to see if the voltage was dropping. One question I do have about this is why it requires a key emulator? I had to buy that extra at the time to make the system work. Does they key on a 2006 have a chip or RFID tag built in that could cause an intermittant problem like this? It does have the flashing key on they dash that goes off when you put the key in. I just don't know much about that system... Thanks for the response.

 

[Mikasa67]

Fuel relay?

Wouldn't the pressure drop when the relay kicked out?

 

[chitown40]

This seems more electrical rather than fuel. Not saying it cannot be a fuel problem, but something so intermittent probably wouldn't starting flashing dash lights. I didn't see you say anywhere if there were any stored codes...

Check all your battery cables and ground wire connections too.

 

[Mikasa67]

This seems more electrical rather than fuel. Not saying it cannot be a fuel problem, but something so intermittent probably wouldn't starting flashing dash lights. I didn't see you say anywhere if there were any stored codes...

Check all your battery cables and ground wire connections too.

It's not storing any codes, wish it would.
Checked the battery cables and what grounds I could find.

When using my monitoring tool one of the monitor point is ECU and ODBII PORT voltage, nothing strange showing up on either. I'm assuming there would be some weirdness if it were loosing ground or positive connection.

Anyone know where and if the runner has a BCU?

 

[vben]

Possibly ignition coil or spark plug wires

 

[chitown40]

I believe it does have at least one BC near the driver lower left dash and kick panel.

No plug wires but possibly a coil pack.

 

[bamma]

Good point, totally forgot to include that information. I do have a remote starter and thought that could be the problem. Took it back to the installer to see if there was any possibility that unit could be failing and act this way. They told me there were no wires cut to install that system, but only tapped in and he highly doubted it could be the problem. They showed me where to test from the key switch to see if the voltage was dropping. One question I do have about this is why it requires a key emulator? I had to buy that extra at the time to make the system work. Does they key on a 2006 have a chip or RFID tag built in that could cause an intermittant problem like this? It does have the flashing key on they dash that goes off when you put the key in. I just don't know much about that system... Thanks for the response.

the car requires a key to start, so to remote start without a key requires emulation. If it is faulty or has a loose connection internally, it definitely could cause your symptoms. Unplug the remote starter and see if the problem goes away. If not that, replace the fuel filter. I saw a t4r with a similar issue in the past and the filter was clogged.

Edit: fyi-the fuel filter is in the tank. It is replacable without replacing the pump but you have to drop the tank. Kind of a PITA. Good luck.

 

[bob3dsf]

Bcu?

For the sake of my edification (any anyone else who might like the same)... What's a BCU??

 

[Mikasa67]

For the sake of my edification (any anyone else who might like the same)... What's a BCU??

BCU = Body Control Unit, it's the computer that controls systems like the heat/ac, lights or pretty much everything else electronic excluding the engine systems.

ECU = Engine Control Unit, computer that controls all engine functions.

Many modern vehicles have other computers dedicated to doing specific tasks, or at least that's my understanding of it.. I'm not a professional mechanic, so maybe someone can school us better on this?

 

[gm350reratliff]

Does the flashing key or security LED light do anything when it does this? Do you happen to know the model of bypass used for the remote start? Is there any mice or squirrels in your area?

 

[Mikasa67]

the car requires a key to start, so to remote start without a key requires emulation. If it is faulty or has a loose connection internally, it definitely could cause your symptoms. Unplug the remote starter and see if the problem goes away. If not that, replace the fuel filter. I saw a t4r with a similar issue in the past and the filter was clogged.

Edit: fyi-the fuel filter is in the tank. It is replacable without replacing the pump but you have to drop the tank. Kind of a PITA. Good luck.

Everything about this screams fueling issue and I have a replacement screen to go in the tank, just have not had the time to drop and replace it. I'm at about 116K miles, so it's time to do it anyway.

The two factors for fueling is 1) pressure 2) volume. If there was a filter issue, wouldn't it restrict the the flow rate or volume of fuel available to the rail? When the injectors release the fuel into the intake and the pump does not have enough volume to keep the rail full and pressurized, wouldn't it show up as a drop in pressure in the rail? I'm not seeing that, it holds 42psi consistently.. I hope that logic is true. This thing is making my head hurt!

I will unplug the remote starter, this will tell me for sure if the information I was given about it not looping through the module is correct.

Thanks for the info.

 

[BlackWorksInc]

Good point, totally forgot to include that information. I do have a remote starter and thought that could be the problem. Took it back to the installer to see if there was any possibility that unit could be failing and act this way. They told me there were no wires cut to install that system, but only tapped in and he highly doubted it could be the problem. They showed me where to test from the key switch to see if the voltage was dropping. One question I do have about this is why it requires a key emulator? I had to buy that extra at the time to make the system work. Does they key on a 2006 have a chip or RFID tag built in that could cause an intermittant problem like this? It does have the flashing key on they dash that goes off when you put the key in. I just don't know much about that system... Thanks for the response.

All 4th Gen 4Runners came with an Immobilizer system, this requires an RFID equipped chip to communicate with the Immobilizer Module and authenticate the driver before letting the vehicle start. I agree with the poster above; at this point I would unplug the remote starter and Key Emulator from the vehicle to eliminate it as a variable.

Also you did not mention what scantool you are using, I'm going to guess since you mention laptop you're using a Chinese TIS Techstream software with mongoose cable? It may be difficult to get some oddball DTCs if you're not using a scantool capable of reading Toyota factory DTCs.

Also since you are using a laptop based scantool are you able to record live streaming data? That might be a huge help in this case as you could post the file and/or video of the failure as so that we can review the data.

I would note that a multimeter may not refresh fast enough to catch an intermittent failure like that.

For the sake of my edification (any anyone else who might like the same)... What's a BCU??

BCU/BCM refers to "Body Control Unit" or "Body Control Module" typically these control non-engine related functionality such as windows, door locks, light timers, ect. So I doubt this could be the issue, unless it was somehow taking down the CAN communication bus.

 

[Mikasa67]

Does the flashing key or security LED light do anything when it does this? Do you happen to know the model of bypass used for the remote start? Is there any mice or squirrels in your area?

No, the light stays off. I don't know the model of that device, but I'm going to take a close look at it next week and can post it then. Nope, no critters been in there, it's still clean under the hood and dash with no gnaw marks..

 

[Mikasa67]

All 4th Gen 4Runners came with an Immobilizer system, this requires an RFID equipped chip to communicate with the Immobilizer Module and authenticate the driver before letting the vehicle start. I agree with the poster above; at this point I would unplug the remote starter and Key Emulator from the vehicle to eliminate it as a variable.

Also you did not mention what scantool you are using, I'm going to guess since you mention laptop you're using a Chinese TIS Techstream software with mongoose cable? It may be difficult to get some oddball DTCs if you're not using a scantool capable of reading Toyota factory DTCs.

Also since you are using a laptop based scantool are you able to record live streaming data? That might be a huge help in this case as you could post the file and/or video of the failure as so that we can review the data.

I would note that a multimeter may not refresh fast enough to catch an intermittent failure like that.



BCU/BCM refers to "Body Control Unit" or "Body Control Module" typically these control non-engine related functionality such as windows, door locks, light timers, ect. So I doubt this could be the issue, unless it was somehow taking down the CAN communication bus.

It will be Tuesday night before I will be able to get back on this. The Key emulator and remote start module are easy to get to, so I'll disconnect that to eliminate it.

The scan tool is a inexpensive eBay find, so I have no doubt the quality is questionable and it won't capture Toyota specific codes. I'll post up the brand and software info next week. It does have the capability to record the data and save it in a .CSV format.

I have a pretty decent multimeter and it's not fluctuating any differently than when it's running normally. Any suggestion on how to better test for the voltage drop?

Thanks for the help.

 

[BlackWorksInc]

Honestly, you're probably testing the voltage drop fine; the comment I made about the meter is less a reflection of the quality but rather the tool itself (even a typically lauded Fluke 88 is sometimes too slow for certain issues.) DMMs (Digital Multi-Meter) only refresh so fast, this issue might be occurring for a only a couple miliseconds, enough to confuse the ECM and almost kill the engine; but too fast for a DMM to register it. A Fluke 88 for example, refreshes only 40 times a second (250 milliseconds) which means anything faster than that refresh rate and it won't register on a DMM. For reference an injector under some driving conditions could be turned on & off in 4 miliseconds or less, you'll never see an accurate representation of that on your DMM.

That doesn't mean it can't been see IF the issue is that fast, but it treads into DSO (Digital Storage Oscilloscope) territory. So for right now we'll want to work with what we have and see how far we can get with what information tools we have (because even if you had a DSO we still don't have a real idea where to hook it up.)

 

[Mikasa67]

All 4th Gen 4Runners came with an Immobilizer system, this requires an RFID equipped chip to communicate with the Immobilizer Module and authenticate the driver before letting the vehicle start. I agree with the poster above; at this point I would unplug the remote starter and Key Emulator from the vehicle to eliminate it as a variable.

Also you did not mention what scantool you are using, I'm going to guess since you mention laptop you're using a Chinese TIS Techstream software with mongoose cable? It may be difficult to get some oddball DTCs if you're not using a scantool capable of reading Toyota factory DTCs.

Also since you are using a laptop based scan tool are you able to record live streaming data? That might be a huge help in this case as you could post the file and/or video of the failure as so that we can review the data.

I would note that a multimeter may not refresh fast enough to catch an intermittent failure like that.

OK, got back early yesterday and had some time to work on this.

The remote start and key emulator are completely removed from the system. No change at all other than I can't start it with my fob. LOL It still stumbles and nearly dies.

-The OBDII scan tool is a "ElmScan 5 Compact Multiprotocol ODB Scan Tool". It is connects to the laptop VIA USB connection.

-Software is called "OBDWiz", more information about it here: https://www.scantool.net/obdwiz/. OBDWiz came with the ElmScan device. It is a very basic/entry level tool.

I was able to capture data for about 20 minutes in both RAW/HEX and .CSV values that I converted to a .XLS and formatted so it could be read more easily. The Runner had several occurrences where it stumbled and nearly died within the 20 minute period I was monitoring, but I can't locate anything strange in the data. The first time was within three minutes of connecting and beginning to monitor.


I put the logged data here:
https://drive.google.com/folderview...VRa2MyeXNhYldialQ2WXVhdkZVWmpiN0k&usp=sharing

I'm going to drop the tank tonight to see if the screen is clogged and or how much water is in there..

Thanks again for any help,