Engine Hesitation/ Stumble

[Rmack]

Sounds like a fuel pump issue. I would check fuel pressure with those symptoms.

 

[wfo9]

with no codes I doubt any sensor airfuel management component issue..

these do not have a fuel test port as most ALL other vehicles have . my guess fuel tank issue pump/screen/wiring / pump relay ..

I don't know how to test fuel pressure on a toyota PITA..but I did and do on other vehicles same issues low pressure.

Not sure why you think there are no codes.... This is a complete misunderstanding with Toyota's. They often don't set CEL even when there is a code. The only ones required to set the light are emissions related stuff.

You have to run TIS and do a health check. This will tell you all the pending and current codes. I'm not saying that will have the answer, but without it.. just making a potentially simple troubleshooting process complex for no good reason.

OP if you have the cable... http://www.toyota-4runner.org/5th-gen-t4rs/243881-tis-install-guide.html

I can help if you have questions... Ask in that thread...

If it is fuel pump related.. would be easy to see with some data logging in TIS if that is the issue and you can recreate the stall. It would be going horribly lean and the fuel trims would be very positive....

Modern cars are basically computers with some mechanical parts attached. You can't troubleshoot most problems without an interface to it. Imagine trying to fix a computer without a way to see the screen or get any data. Waste of time.

And this is why they don't have things like fuel pressure ports anymore. I wish they did.. but there are other ways to diagnose in 2017.

 

[catrains]

I totally disagree with your code comment ..engine codes if they exist with be displayed, . miss fires/improper fuel /air ratio and then we get into the cat converter monitoring..

TOYOTA does not have a test port also the PCM does not have ability to monitor fuel pressures . if it did then with a bad fuel pressure a code would throw.

so if you have intermittent stalling with this vehicle fuel pressure is suspect .. possible the fuel level sender is bad indicating more fuel than in the tank LOL.. seen that before ..

If TOYOTA as YOU say does not indicate a sensor data failure then this would be an EPA violation ..

pending codes will not indicate on the display but if you have an engine stall then that would change to a confirmed failure code.
the PCM has memory so if the sensor keeps throwing bad data the code will be confirmed and you cannot clear it in these new vehicles .. another EPA rule .

 

[wfo9]

I totally disagree with your code comment ..engine codes if they exist with be displayed, . miss fires/improper fuel /air ratio and then we get into the cat converter monitoring..

TOYOTA does not have a test port also the PCM does not have ability to monitor fuel pressures . if it did then with a bad fuel pressure a code would throw.

so if you have intermittent stalling with this vehicle fuel pressure is suspect .. possible the fuel level sender is bad indicating more fuel than in the tank LOL.. seen that before ..

If TOYOTA as YOU say does not indicate a sensor data failure then this would be an EPA violation ..

pending codes will not indicate on the display but if you have an engine stall then that would change to a confirmed failure code.
the PCM has memory so if the sensor keeps throwing bad data the code will be confirmed and you cannot clear it in these new vehicles .. another EPA rule .

You can argue all day about it. In the end... if you want the truck fixed. read it with the factory scan tool that will tell you everything the ECUs have set. It will take all of 30 seconds if it is just a code. If no codes... then some logging and clues can be found in other areas. Never assume anything until you have tried or seen it yourself... I thought the same as you until I started messing with modern Toyota's.... They are the odd man out in terms of diagnostics.

The other option is throwing parts and obvious maintenance at it... Good luck either way.

 

[ADVnut]

OK, guys. Just a small update with no resolve at this point.

I am all about collecting data, but am having a hard time collecting anything meaningful.

I am fairly new to Techstream, but I connected things up and ran the health test. Nothing showed up in the list as far as error codes or problems. I tried to collect live data when driving to hopefully collect something when it stalls, but when doing so got a fatal error. I spent a good portion of the time fiddling with drivers and settings in the software to try and get the hacked copy to behave.

At this point, I was not so politely reminded that I am supposed to be traveling in said vehicle all next week and I "should quite screwing around connecting the car to the computer". I gave up and had it towed to the dealer for their "Diagnostic Testing Service". I'll report back with their findings.

In the back of my mind I keep thinking its some magnetic based sensor such as crankshaft/ camshaft or something similar. Maybe the sensor is going bad and is intermittent.

Thanks again for the assistance and replies.

Will update when I have more info.

 

[BlackWorksInc]

I totally disagree with your code comment ..engine codes if they exist with be displayed, . miss fires/improper fuel /air ratio and then we get into the cat converter monitoring..

TOYOTA does not have a test port also the PCM does not have ability to monitor fuel pressures . if it did then with a bad fuel pressure a code would throw.

so if you have intermittent stalling with this vehicle fuel pressure is suspect .. possible the fuel level sender is bad indicating more fuel than in the tank LOL.. seen that before ..

If TOYOTA as YOU say does not indicate a sensor data failure then this would be an EPA violation ..

pending codes will not indicate on the display but if you have an engine stall then that would change to a confirmed failure code.
the PCM has memory so if the sensor keeps throwing bad data the code will be confirmed and you cannot clear it in these new vehicles .. another EPA rule .

Actually he's sort of right here. OBDII regulations allow 1 trip before an MIL needs to be set for most DTCs under the OBDII umbrella. This means a "Pending DTC" can be set and stored in the memory, but an MIL will not be set. When the fault occurs a second time the DTC is upgraded to a "Current DTC" and the MIL is turned on. Additionally for some DTCs/systems if only a pending DTC is stored and on the next test cycle and/or a certain number of drive cycles occurs without a second trip the DTC will be cleared and a "History DTC" will be stored for another set of drive cycles.

The OP already admitted that they've been disconnecting the battery and resetting the system, so it's entirely possible any DTCs that they had could have been Pending DTCs that have not yet upgraded to Current DTCs. Additionally I have seen faults that do not consistently trip an MIL or even a Pending DTC; it's a bit rare but does occur.

OK, guys. Just a small update with no resolve at this point.

I am all about collecting data, but am having a hard time collecting anything meaningful.

I am fairly new to Techstream, but I connected things up and ran the health test. Nothing showed up in the list as far as error codes or problems. I tried to collect live data when driving to hopefully collect something when it stalls, but when doing so got a fatal error. I spent a good portion of the time fiddling with drivers and settings in the software to try and get the hacked copy to behave.

At this point, I was not so politely reminded that I am supposed to be traveling in said vehicle all next week and I "should quite screwing around connecting the car to the computer". I gave up and had it towed to the dealer for their "Diagnostic Testing Service". I'll report back with their findings.

In the back of my mind I keep thinking its some magnetic based sensor such as crankshaft/ camshaft or something similar. Maybe the sensor is going bad and is intermittent.

Thanks again for the assistance and replies.

Will update when I have more info.

If you have TIS Techstream Software, what I would recommend trying is to find a safe place to drive the vehicle with the scantool hooked up. Then select "Engine" (it might be labeled ECM as well) under the modules list, then on the left hand menu list select "Utility". You should see an option labeled something along the lines of "Enable Check Mode" or just "Check Mode". Follow the prompts on the pop-up to enable "Check Mode".

What Check Mode does is tighten testing parameters and set the vehicle to a "One-Trip" setting. This means that rather than going Pending DTC -> Current DTC and needing the fault to occur twice; it will go straight to Current DTC, set the MIL and flag Freeze Frame data along with it. This is helpful for more inconsistent issues were a fault is not always showing up as a MIL or even a DTC.

~

On a side note, it could be something like a crank position sensor (not entirely sure it is or isn't). We saw a lot of the new 3rd gen Tacomas stall out and stumble because of a poorly designed crank position sensor (hence why we have the H0H Recall now) and those oddly would not set a DTC for the sensor itself; I guess the failure was too fast for the system to detect, but slow enough to stall out the engine? Not entirely sure why it wasn't consistently picked up by the ECM.

 

[wfo9]

OK, guys. Just a small update with no resolve at this point.

I am all about collecting data, but am having a hard time collecting anything meaningful.

I am fairly new to Techstream, but I connected things up and ran the health test. Nothing showed up in the list as far as error codes or problems. I tried to collect live data when driving to hopefully collect something when it stalls, but when doing so got a fatal error. I spent a good portion of the time fiddling with drivers and settings in the software to try and get the hacked copy to behave.

At this point, I was not so politely reminded that I am supposed to be traveling in said vehicle all next week and I "should quite screwing around connecting the car to the computer". I gave up and had it towed to the dealer for their "Diagnostic Testing Service". I'll report back with their findings.

In the back of my mind I keep thinking its some magnetic based sensor such as crankshaft/ camshaft or something similar. Maybe the sensor is going bad and is intermittent.

Thanks again for the assistance and replies.

Will update when I have more info.

Next time.. you could see if it was fuel related by following the basics procedure here...
http://www.toyota-4runner.org/5th-gen-t4rs/246102-favor-please-someone-tis.html

If TIS is getting all the live parameters... it's slow and quirky.. but if you limit the data list it does fine (5 or less parameters at a time is best) For fuel issues (bad fuel pump clogged injector...) you can look at the short term fuel trims, long term fuel trims and wideband 02 sensors. The O2s should read near 1.0 lamdba on both banks and all the trims should be pretty low. The only time it should read different is under hard acceleration...

If it is spark related (bad plugs, wiring, or crank position sensor)... You should see missfires. there are parameters to monitor misfires on each cyl... but I have not messed with that much. The logic to set an actual code for misfires is pretty fuzzy, so it is often best to monitor the actual misfire counts.

 

[EddieV4runnin]

You can argue all day about it. In the end... if you want the truck fixed. read it with the factory scan tool that will tell you everything the ECUs have set. It will take all of 30 seconds if it is just a code. If no codes... then some logging and clues can be found in other areas. Never assume anything until you have tried or seen it yourself... I thought the same as you until I started messing with modern Toyota's.... They are the odd man out in terms of diagnostics.

The other option is throwing parts and obvious maintenance at it... Good luck either way.

:fish: Toyota is easy....try Hyundai nothing in the factory service manual matches to what’s on the vehicle. I’ve had to make my own diagrams to repair them.

 

[EddieV4runnin]

Actually he's sort of right here. OBDII regulations allow 1 trip before an MIL needs to be set for most DTCs under the OBDII umbrella. This means a "Pending DTC" can be set and stored in the memory, but an MIL will not be set. When the fault occurs a second time the DTC is upgraded to a "Current DTC" and the MIL is turned on. Additionally for some DTCs/systems if only a pending DTC is stored and on the next test cycle and/or a certain number of drive cycles occurs without a second trip the DTC will be cleared and a "History DTC" will be stored for another set of drive cycles.

The OP already admitted that they've been disconnecting the battery and resetting the system, so it's entirely possible any DTCs that they had could have been Pending DTCs that have not yet upgraded to Current DTCs. Additionally I have seen faults that do not consistently trip an MIL or even a Pending DTC; it's a bit rare but does occur.



If you have TIS Techstream Software, what I would recommend trying is to find a safe place to drive the vehicle with the scantool hooked up. Then select "Engine" (it might be labeled ECM as well) under the modules list, then on the left hand menu list select "Utility". You should see an option labeled something along the lines of "Enable Check Mode" or just "Check Mode". Follow the prompts on the pop-up to enable "Check Mode".

What Check Mode does is tighten testing parameters and set the vehicle to a "One-Trip" setting. This means that rather than going Pending DTC -> Current DTC and needing the fault to occur twice; it will go straight to Current DTC, set the MIL and flag Freeze Frame data along with it. This is helpful for more inconsistent issues were a fault is not always showing up as a MIL or even a DTC.

~

On a side note, it could be something like a crank position sensor (not entirely sure it is or isn't). We saw a lot of the new 3rd gen Tacomas stall out and stumble because of a poorly designed crank position sensor (hence why we have the H0H Recall now) and those oddly would not set a DTC for the sensor itself; I guess the failure was too fast for the system to detect, but slow enough to stall out the engine? Not entirely sure why it wasn't consistently picked up by the ECM.

F it let’s throw parts at it. I’m surprised nobody has said check your starting and charging system. First things first :baby:. Most of the concerns I’ve had that other shops couldn’t repair were things that could’ve been resolved with basic diagnostic strategy.

 

[BlackWorksInc]

F it let’s throw parts at it. I’m surprised nobody has said check your starting and charging system. First things first :baby:. Most of the concerns I’ve had that other shops couldn’t repair were things that could’ve been resolved with basic diagnostic strategy.

I wasn't saying he should throw parts at it, rather providing an example that DTCs aren't always shown just because a vehicle is having an issue (another example would be 4WD systems on Toyota Trucks before about 2015 as they didn't store DTCs, provide a data list, or even have a module that communicates on the CAN Bus). If anything I'd say if you ruled out any abnormalities in fuel and spark then that'd be something else to test.

But Check Mode is as good a place as any to start if you have a scantool and can sort of make the issue occur.

 

[catrains]

about 12 yrs ago a jeep had a random engine stall and then no start . this was back when the PCM was not all that smart compared to today.

vehicle towed then off truck it would start .. checked for any codes and fuel issues ....everything looked perfect . looked up this issue on forums and a dodge tech and others stated the CPS module would fail on its getting heated up and to measure resistance when it cold / then heated . did the OHM test and replaced CPS problem solved the resistance changed from hot to cold ..

vehicle was checked out several times at dealership.. I did fix it ..
today these PCM setups are quick and helps fix the electrical failures ...
the stored failure codes help do the fix , unlike years ago ..

 

[ADVnut]

Thanks for the additional replies. Small update:

So at this point we are pretty much throwing parts at it. It's been at the dealer for about a week. According to tech, no codes are showing up. In his tests fuel pressure is cutting out. Reproducable in right hand turns. The fuel pump signal isn't being cut but pressure is.

Next step is to drop tank to inspect wiring and possibly replace pump or filter.

He stated he will reach out to Toyota for more info as he is perplexed as well.


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[Argyle Edison]

Thanks for the additional replies. Small update:

So at this point we are pretty much throwing parts at it. It's been at the dealer for about a week. According to tech, no codes are showing up. In his tests fuel pressure is cutting out. Reproducable in right hand turns. The fuel pump signal isn't being cut but pressure is.

Next step is to drop tank to inspect wiring and possibly replace pump or filter.

He stated he will reach out to Toyota for more info as he is perplexed as well.


Sent from my Pixel 2 using Tapatalk

Please keep updating. I might have issues with right hand turns as well...

 

[ADVnut]

Please keep updating. I might have issues with right hand turns as well...

Will do. Today I am trying to convince Toyota that they don't need to dismantle and remove my ARB drawers in the trunk to inspect fuel related wiring. From my recollection and pictures there is only a single wire that runs across the rear of the bare trunk area.

If anyone know otherwise please let me know.

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[gm350reratliff]

IIRC, the wiring to the fuel pump runs along the inside of the left frame rail to the tank.

 

[ADVnut]

IIRC, the wiring to the fuel pump runs along the inside of the left frame rail to the tank.

Thanks. That's what I recall as well. I also don't remember much wiring under the driver side rear side panel or wheel hump. The dealer is wanting to uninstall the bolted in drawers and remove the side panel to troubleshoot/ inspect wiring.

Anyone had the rear apart lately and can confirm if there is anything fuel related under the left hand rear side panel/ hump?

Where does part #4 in the diagram live?

:cheers:

 

[gm350reratliff]

I'm pretty sure part #4 also lives on the inboard side of the left frame rail, just rearward of the fuel tank.

There are wiring harnesses that go on each side of the cargo area behind the interior panels but I don't think there's anything in those harnesses that go to the fuel tank or pump.

 

[ADVnut]

I'm pretty sure part #4 also lives on the inboard side of the left frame rail, just rearward of the fuel tank.

There are wiring harnesses that go on each side of the cargo area behind the interior panels but I don't think there's anything in those harnesses that go to the fuel tank or pump.

Thanks. Its connector Q6 in the diagram, just hard to determine the location. Thanks for confirming my line of thinking.

 

[Scowling Tuna]

Dead thread, but was this ever resolved? I get a little bit of hesitation on throttle input (like when I think the truck should potentially downshift). I've changed the settings on my Pedal Commander, thinking that maybe it's the issue (or related). Did that this morning, so maybe it's a placebo affect for now, dunno.

 

[az4runner02]

Any update?

Think a few of us would love to hear what it was…lol