I have a 2006 GX470. Was driving it down a gravel road on a downhill the other day, and the engine suddenly just died. I coasted to a stop, turned the key fully off and it started fine. I then proceeded to drive a couple hundred miles with many stops and starts over the next few days without any issues.

last night, after driving the vehicle for about 6 hrs road trip, I had it parked and running while the dogs ran around. Could hear the idle dropped really low then suddenly really high. When I got back in the car to leave, it had just died. Turned the key off, started up normally just fine. Moved a few feet, engine dies again. Tried various times to start it, this time without turning the key to the fully off position, and It would not stay running for more than a couple of seconds each time. It would crank and fire up, but it was like there was no fuel coming to keep it going. Immediately would die and I couldn’t even keep it running long enough to put it in gear.

Turned the key fully off again, and the next time it started right up like completely normal. Drove it 60 miles home without issue.

so I’m wondering what I need to do to this thing. To me it seems like a fuel pump or throttle issue but I don’t know exactly where to start. I was originally thinking about alternator or battery, but it doesn’t really seem like any electrical systems are impacted. Truck has just over 150k miles.

 

Hmmm. To me what you described sounds like a fuel delivery issue. It could be the fuel pump/filter/electrical connection? Is your gas tank less than 1/4 tank when the issues start? Maybe the pump is old/tired and is overheating due to not being submerged in the gas for cooling, but when driving the gas sloshes around enough to keep the pump cool? This is all conjecture of course......

 

Sounds like the fuel pump is about to go nite nite. How many miles on your GX?

 

This was happening with lots of fuel in the tank, ~3/4. Truck has 152k miles on it. I was thinking maybe fuel pump but I figured that would be a more catastrophic thing, working one minute and toast the next. Do those slowly start to fail?

 

Check your battery voltage.

I had a battery die once after going over a speed-bump. What happened was one of lead plates inside had broken off, fallen to the bottom of the battery, and shorted against adjacent plates, dropping the voltage below 10v. If you go offroad frequently (or over a lot of speed-bumps..) getting an AGM battery might be a good idea.

Chip H.

 

did not check the battery yet. It was new about a year ago.

 

Might just be a clogged Fuel Filter. Do that before the pump, and absolutely with a pump if that's what it comes down to. Hopefully its a current issue.

 

Battery Checked out ok and there was no codes. I read somewhere that the fuel filter on this vehicle does not require any maintenance. I’m definitely a bit stumped on this one. What also gets me is why it would not run if I tried to start it without turning the key fully off, but once I turned it fully off and tried again, it would start immediately like nothing happened. It’s like being fully off reset something.

 

With those miles, I'd recommend looking at/considering replacing the fuel pump. I got some bad fuel, recently, and when I was having the tank dropped and cleaned, I just happened to mention to the mechanic that my '05 GX had a little over 192,000 miles on it. He asked if I'd replaced the fuel pump (which I hadn't) and said that's part of "normal maintenance" every 150,000-200,000 miles. I've owned a number of vehicles over the years and had never heard of this as "part of normal maintenance." But, sure enough, a quick Google search did confirm that's "normal." Granted, it's a bit pricey if you go with a legit Lexus pump (I think I paid about $950 to have the tank dropped, drained, physically cleaned by hand (i.e. wiped with a towel and left to dry overnight), new Lexus fuel pump with "filter" (it's really just a sock over the intake) installed, the lines purged and cleaned with a cleaner solution, and everything reassembled and tested. I know that's a bit of an unexpected ouch but, when you break it down, only comes out to about 0.475¢ per mile and really does make a noticeable difference in performance.

As an aside, even if it isn't the fuel pump, it's still wise to just go ahead and do it now so you're not stranded on the side of the road later.

 

The way the engine is dieing and the behaviour when the key is partially vs. fully turned off makes me think it could be related to the anti-theft chip in the key...do you have another key you could use for a while and see if the problem returns?