2008 GX470.....driving from Houston to Brckenridge CO..car died 3 times on the way...engine started missing a bit then completely died. First time n of Dalhart TX pulled off the road and restarted in a few minutes ran ok for about 30 miles died again. Restarted in a few minutes, filled up and drove 120 miles to Trinidad CO no problems....stopped at Toyota dealer in Trinidad, ran full diagnostics, said fuel mixture would run too high, car was fine now, maybe bad gas. Drove 150 mi no problem to Co Springs. Car died again climbing up to Breckenridge, pulled into gas station, shut down, filled up, restarted and no problems the last 100 miles into Breckenridge? Any ideas? Only commonality when the car died was that I was at half tank of gas. If fuel pump issue should full analysis have showed that?

 

When I was in the San Juans recently, we drove over 13000' without a single problem but I did pass a few stalled jeeps that were vaporlocked because of the ethanol in the fuel evaporating at the lower air pressure. I don't know if our fuel injected motors are susceptible to this or not.

 

I remember going to Angel Fire(8500ft) from Albuquerque(5300) in an Olds Cutlass and after the car sat for 2 days the car would not start when trying to leaving Angle Fire. A local fella advised us to remove the gas cap & disconnect the battery cable for a 10-15 minutes. Problem solved! Not sire if this help, but I thought I'd share my high altitude car troulbes. Good luck

 

Did he mean it was running too rich? Because cars tend to run rich at high altitudes (less oxygen means the air/fuel ratio is unbalanced towards the fuel side of things).

I believe that the 2008 uses a MAF sensor to read air flow, and it doesn't adapt to rapid changes in altitude as well as the MAP sensor used on later vehicles. Try taking a dinner break or fuel stop every so often.

Chip H.

 

Altitude shouldn't affect fuel injected cars to the point of them stalling out and quitting. It might aggravate some other problem, but they should make the transition smoothly.

 

Altitude change from Houston to Dalhart would be minimal, so I dont think thats the problem. The problem sounds like its more heat related after extended runs.
If you had no CEL lights or codes stored, the problem was likely fuel related. You might have the fuel pressure checked to see if its within specs and change the fuel filter if it has one.

 

A dirty/clogged fuel filter was my first thought when I read the OP.

When a fuel filter starts to collect debris, that debris will normally sink to the bottom of the filter, and, as long as the car is in a relatively level position, the vehicle should perform normally. However, when there are periods of time when the vehicle is driving up or down relatively steep grades for, at least, a little while and when the car is no longer level, the debris can partially or completely block the flow of fuel.

Because the quality of gas has come a long way over the decades with regard to being more consistently clean, problems with clogged fuel filters have become relatively rare. The last time that I had such a problem, the first signs of an issue came when I was driving on terrain that was such that I was going up and down relatively steep hills. The engine would start to sputter because debris in the filter was blocking the flow of fuel, but, if I got onto level terrain and let the car sit for even a short while, that debris would, once again, settle to the bottom of the filter, and the engine would return to completely normal performance.

I don't know anything about fuel filters on the GX, but it is something that you might want to check out.

 

Fuel filter is non serviceable. Located inside the gas tanks. It is supposedly self cleaning whatever that means.

 

That doesn't surprise me since I couldn't find any mention in the owner's manual of a fuel filter or servicing it.

What I would wonder, though, is if that means that the fuel filter is truly incapable of becoming clogged under any circumstances or if it can clog and, when that happens, the gas tank needs to be dropped to perform service.

In any case, from the OP's description, it does sound like something is temporarily restricting the flow of fuel to the engine.

 

Actually, Dalhart TX is over 4,000 ft.
Had no indications of any heat related issue.
Toyota dealer performed full diagnostic. Wouldnt a fuel pump/ fuel pressure issue show up in the diagnostic analysis.

The Trouble Code Report indicated:
Code: P0171; Descr: System Too Lean (Bank 1); Summary: Icon E
Code: P0174; Descr: System Too Lean (Bank 2); Summary: Icon E

Freeze Frame Data Report for P0174; Out of Range Items:
Short FT #1 = 0.0
Short FT #2 = 0.0
Long FT #1 = 36.7
Long FT #2 = 37.5

Not sure what the above codes & data reports indicate.

Thanks for your replies.

 

Google search on P0171 came up with this:

http://engine-codes.com/p0171_lexus.html

I would work down their list. Intake leak of some kind is plausible. Make sure the air cleaner box has a good seal, and that you're using a factory filter.

Chip H.

 

Short FT and Long FT refer to fuel trim. As the long term fuel trim are positive numbers, it indicates the engine electronics are adding fuel (increasing the fuel injector pulse width) to make up for a lean running condition, which is shown in the P codes. Chiph9 is correct, start by looking for an intake air leak.

You also mention that each time the engine stalled the fuel tank was at about half full? IIRC in another post someone mentioned replacing the jet pump in the fuel tank. In an upside down U shaped gas tank, the jet pump moves gas from one side of the tank to the other; as the fuel pump removes gas from the reservoir on one side, the jet pump picks up the gas from the reservoir on the other side and moves it across.

Is the stalling problem still occurring?

 

I've been driving around the Breckenridge area for the last week with no problems. Mostly short trips of 20 miles or less....Mainly been running at 9,500 to 11,000 feet. Won't be leaving here for another week when I'll be going from 11,000 feet back to Houston at 33 feet above sea level in one day.
Talked to a tech at the Lexus dealer in Colorado Springs. His opinion was MAF may be dirty and not able to respond quickly enough to altitude/ gas formulation changes. They offered to check it out of course but it's a 2 hour trip from Breck to Co Springs.
Don't mind stopping from time to time on the way back to Houston to let the electronics reset but sure would hate to get stuck as some places along the way are a long way from nowhere.

 

It's not just the MAF sensor, but the readings it reports to the computer.

The software inside the ECU has data smoothing algorithms (so it doesn't overreact to small spikes in the values) and if you change altitude quickly it can take a while to catch up.

If you drove through a warm front quickly it might have a similar effect, as the hotter air is thinner, just as if you had climbed a few hundred feet.

Chip H.

 

You could stop at Kuni Lexus in Greenwood village as well. Its a bit closer than the Springs are. I worked there for a few years, and some of the techs there know their stuff very well.

Not only that, they just moved into a new location with a movie theater and a pool table to goof off with while they have your car in the shop