Just wanted to post this question to see if anyone has ideas or maybe has ran into it. My 4runner is not typical.

So the situation:
- 3/4 tank of gas
- Crawl box with 4.7s engaged
- stock tcase in 4hi
- automatic transmission in drive

Was on a very steep climb earlier this week in Sand Hollow Utah and it just cut out on me. Lost all power and rolled back into some rocks. Luckily no damage. Did it again later that day but I was able to use the e-brake and park to save it.

Seems to only happen when the 4.7s are in use and fires right back up like nothing happened afterwards.

I've gone up pretty steep things with mine (5-spd, case doubler, 6.6:1 in dual low) and never had an issue.

Are you hard on the throttle when it does this? Potential for some wiring issue when the multiplied torque shoves the drivetrain around more than normal?

And it did this at a decent RPM? Probably less of an issue with an auto trans and tq converter, but I've occasionally stalled mine (before I had the doubler). And they don't like restarting when they die under a load like that, I guess there's extra fuel still in the intake.

At 3/4 tank, it's unlikely to be a fuel supply issue, at least in terms of the fuel pump sucking air.

I'm sure there was a lot of distraction in the moment (to say the least) but did the dash lights do anything weird you can recall? Any OBD2 codes stored (they might not set a CEL)?

There was no CEL after restart and I did not have my reader with me. Gonna start carrying it.

Here is a video of it happening, I think I came off the gas to cover the brake pedal when it happened.

Mystery stall. - YouTube

If there are pending/stored codes, they'll still be there until you clear them. Might be worth seeing. But even if it got fuel starved, it probably happened faster than the OBD2 would ever pick up.

Yeah, don't know what to say on that, you're partly over the top and not pulling as hard at that point, and the motor just clicks off. I'd be looking at an electrical issue. Which is obviously hard to find when it normally doesn't do it.

I don't have an answer, just wanted to say nice SAS
At least it wasn't on the chute
What's interesting is the transfer case was kicked into neutral if you were able to roll back like that

No, the torque converter would allow slip - especially once the pump isn't pumping. It wasn't in Park, it was in Drive...

-Charlie

Did you not have vacuum assist when you went for the brakes? Might have a bad one-way valve in the hose between the intake manifold and the brake booster.

I stood on the brakes and it felt like nothing was happening during the rollback. Thanks for the idea, that gives me something to start with.

Not related to the engine dying, of course. But even coming off full throttle and having the engine die suddenly (no engine vac) the booster still should have a couple of braking's worth of vac stored up.

In *really* cold weather the check valve on mine started to stick shut (preventing any engine vac from getting to the booster) until it warmed up under the hood, and boy, without power assist the brakes on a 4Runner are not very useful.

Pretty quick and easy part replacement.

Looked for leaks using an un-lit propane torch and did not find anything. I did find a leaking/cracked line on the evap side. I think it was the line that leads to the tank vent. Not sure if that would have caused it but I fixed it and will continue the hunt.

He's talking about the check valve in the booster line, which you wouldn't find with propane. The hose is still good, just the valve is stuck open. Good on you for finding other vacuum leaks though!

The stalling is still a mystery though. I hope you can find the answer.

-Charlie