100 VX 2UZ-FE Stalling (1 Viewer)

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Joined
Jan 22, 2010
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10
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48
Location
South Africa
Website
100vxv8.wordpress.com
Hi,

On my usual 3km trip to work this morning, the engine (2UZ-FE with 142000km) stalled at the last three traffic lights when I came to a stop (foot on brake and car in drive). I put the car in park, turned the key to "off" and then started it again. It seemed to idle a little rough for a second and then was happy. No lights on dash whatsoever (i.e. all normal). Took off and got to next red light, and same thing again.... and then again....

When I got to work, I stopped in the parking lot and it happily idled away smoothly and I could rev it etc - acted like a happy engine. I could not recreate the stall (but I did not drive it around - just revved etc and idled in the parking bay). I tried in park, drive etc - no stalling.

Notes:
-------
- When It drove between the lights, it acted completely normal. Gear changes were fine and engine was fine.
- Voltage, oil pressure and temp were all in their usual range

- I figured it could be the ignition turning off so I fiddled with the key while it was idling in the parking lot and even turned it slightly towards the off position but it did not stall.

- The tank is full as of last week Tuesday and I've probably done 50km since then.

- Throttle body is clean and air filter was replaced 200km ago when it was last serviced

- Checked MAF sensor and it looks visibly clean. I last cleaned it about 1000km ago.

- Key is undamaged and the same one I've used for years. I also tried the spare with the same results

- Although the engine was chipped a few years ago, I removed it soon after.

- I replaced the fuel pump and fuel filter about 3 months ago - both OEM

- I removed and re-inserted all the fuses behind the passenger kick panel, and the ones under the hood. I also removed and re-inserted quite a few of the plugs behind the kick panel (all to no avail).

- When I went for the drive, I had the radio and AC off so it was pretty quite. I noticed a relay behind the dash (located somewhere behind the steering wheel) was switching on and off randomly about every 10-15 seconds. Could be a red herring or a clue...? Maybe that's normal and I just don't normally pay that much attention.

- The stall happens in Drive or Neutral so its not a TC issue

Here is a video I took with my phone of it playing up:

2UZ-FE Stalling - YouTube

You can see that its in neutral. My foot is on the brake and am not touching the accelerator. The engine is doing what the rev gauge shows (i.e. the gauge does not just miss-read). See how it almost stalls, then revs up a bit, then almost stalls again, then revs and then almost stalls so badly that the dash lights up, but then it recovers again. I didn't restart or anything during the video - the engine revs went right down to almost zero but then recovered.

On other occasions, it would not recover and I would need to restart.

Based on this, its definitely isolated to the engine. The way it almost dies and then recovers indicates it cant be a "binary" failure like the immobiliser or something. IMHO , It must be :

1) a sensor or something else that sends the ECU on a spin...
or
2) a fuel supply issue

Any ideas???
 
I am just guessing here, but the first two things that come to mind are:

1) bad fuel or fuel delivery: (any chance of water or particulate in the fuel? is the tank venting properly? crimped fuel line? who installed the fuel pump and filter?)

2) exhaust back pressure: (any chance your catalytic converter is clogged? crushed exhaust pipe? potato in the tailpipe?)

Curious to hear the solution.
 
FSM points to "Fuel pump control circuit".
 
Last edited:
Sounds like a bad batch of fuel to me. The fact that it happened while slowing down and stopping for a red light may be pure coincidence, or it might have something do to with water in the fuel getting pushed up toward the fuel pump as you are slowing down, and the moisture reaches the engine as you are sitting there causing the rough idle. Throw a little Drygas in the tank and see if it helps. If it doesn't, I'd look at the filter or maybe even the pump since they were both just replaced...could have gotten a lemon replacement unit. It happens.
 
Spot on Fuzz. I drained the tanks and put in new fuel. All perfect now! Thanks.
 
Atta Fuzz!
 
You wont believe it but the issue was not actually due to bad fuel. Here is a write up I did on LCCSA forum:

A while ago I pronounced that I thought the problem was fixed as it had not occurred for several days. On Wednesday last week I decided to start the process of calibrating my MPGuino fuel economy gauge as per my blog

To do this I needed to fill the tank completely and then drive for a while and then fill it up again, calculating exactly how much had been used and the km travelled. After filling the tank, the stalling happened again and continued from then on.

I then starting thinking and couldn't help but notice that if you look through the full case history of this issue, you can see that the stalling only ever happened when the tank was full. I had not noticed this as my motivation for syphoning fuel out the tank was to remove water and/or add water remover - both of which solved the problem. When I filled it up again, I thought that this was re-introducing water from my jerry cans and hence causing the issue again.

In reality, there never was any water or any other fuel quality related problem. The pressure was perfect, the throttle body was clean and all the sensors and other stuff were perfect... the problem was in fact that the engine stalled because it was flooded! The damn thing had too much fuel, not too little!

And here's how this happens:
screenshot-9.png


The EVAP system is there to ensure that as fuel vapour leaves the tank, it is absorbed in the charcoal canister and then when the engine runs, it is sucked into the manifold via vacuum and burned. This improves economy and reduces emissions.

The system has a solenoid valve called the TVV (thermo vacuum valve) that is normally closed when the engine is off. This ensures the vapours cant be vented to the atmosphere. Once the engine reaches operating temperature, this valve opens and allows the manifold vacuum to suck the vapours out the charcoal canister and into the engine for combustion.

Now, lets for argument sakes, say that our name is Paul and you have a VX with a second tank fitted high up between the chassis and spare tire. Lets also say that you filled up at night (when its cold) and just before the fuel price shoots up. You have all the time in the world and the attendant fills it to the absolute brim and shakes the car to make sure its "full full full". Lets also say that the next times you filled it up, you were calibrating an economy gauge and again filled the car to the absolute brim and it was either in the early morning or in the evening (fairly cold again). Under both these conditions, the fuel level is actually above the top of the main tank, and is flowing up the breather towards the charcoal canister... Now, its summer and you drive off to work. The fuel heats up and the car heats up. By the time you get 2 km down the road, the pressure in the tank starts to build. Then as you reach operating temperature, the TVV opens. Fuel then sucks up the breather and fills the charcoal canister. Once that's full, it progresses into the manifold and literally pours fuel into the inlet. With the revs up, the engine manages to burn this off and keep going, but then the robot turns red. You take your foot off the accelerator and the butterfly valve closes. The engine now has a pool of fuel in the manifold and a bit of air, creating an extremely rich mixture with too little air and too much fuel, flooding the engine. This cycle keeps happening whenever you drive and then take your foot off the accelerator, but if you stop and idle for a while, then there is not enough vacuum to suck fuel out the cannister and it idles fine. Drive off again, sloshing fuel around and creating enough vacuum and the manifold is swamped in fuel again...

That was the theory I came up with at work yesterday and when I drove home, it stalled as normal. I pulled into the driveway, popped the hood and removed the pipe going from the tank to the charcoal cannister, and sure enough fuel sprayed out. I used my compressor and blew into the cannister and got about 500ml of petrol out. I opened the fuel cap and again, fuel bubbled out... I took about 5l of fuel out the tank and went for a drive... all perfect. Put the fuel back - stalling problem again and cannister full of fuel!

So... long story short.... if you have a second tank that's high up and gravity feeds into the main tank, don't overfill as you will end up with it finding its way into your manifold and flooding the engine.
 

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