06 LX stalling on rough road (1 Viewer)

[burke3265]

Having an issue with engine cutting off at highway speed then coming right back on. From 2500Rpm to zero check engine then back to 2500. Fuel pump relay was replaced by mechanic per code. Condition is very intermittent. Second trip back to mechanic and no codes and extended test drive by him with no issues.

Car sat today in 102 heat and started doing it again on freeway on very bumpy section of road - surging now as opposed the full rpm to zero.

Check battery connectors and ground and all seemed tight. Rattled the connections around the relay and started back up and drive around rough parking lot and condition continued.

Checked gas cap and it came off easy - almost too easy. Took it al the way off and then Clicked back on hard to close and car is now running ok (over same stretch of highway.

Problem has come up after almost every fill up, then never happens again until the next time. Under heavy acceleration the first time after a fill up - I thought maybe was bad gas after a non brand fill up but have runtwo tanks through and the car will drive flawlessly for hundreds of miles until it happens again.

So question if the cap is faulty and working itself loose over bumpy roads and losing vacuum would the engine react this way? Everything else mechanical you'd expect to see codes or easily repeatable failures like a fuel pump going? I and my mechanic are hesitant to start throwing parts at it (that's why I like him) but does any of the above sound familiar and if you've any input on what a loose gas cap would do I'd love to hear it.

 

[ITRJ]

Was there a lot of vacuum in your tank when you release the cap after driving?

 

[burke3265]

Was there a lot of vacuum in your tank when you release the cap after driving?

Come to think of it no - which is why it was so easy to get off? Gas cap is a turn till one click kind that is always a PITA to get off normally. This is starting to get interesting. I'm almost due for a fill up and will see if I've got vacuum tomorrow - intermittent seal on the gas cap that is losing vacuum over bumps?

 

[ITRJ]

Too much vacuum in your tank would be a bad thing. The tank ventilation has to allow air into the tank as the fuel is depleted otherwise you could have fuel supply problems. Like if you were to drink a coke out of a glass bottle without letting air back into the bottle.

 

[ITRJ]

Does it happen immediately after a fill up?

 

[burke3265]

Does it happen immediately after a fill up?

So this got the better of me and I just went to fill up.

The cap came off ok, not a huge whoosh - normal. It's a "one click" type cap. The o ring in it looks fine - but who knows. I made sure to make cram it on probably more than one click and just took a highway drive over the same patch of road that gave me trouble today - no issues. If something is loose it should have happened again - my thinking if a ground is loose or a connection corroded it would do it again on the same road. Again no issues - I'm hopefully optimistic.

Going to let it bake in the sun tomorrow like today and drive it again when the truck has been sitting all day in the sun just to rule out any heat related issues.

Is it always going to end up being a gas cap? I'd be good with that!

Thanks ITRJ for responding and asking the questions. This has been bizarre to say the least. Bought car in December and it's been on 3 trips to Tahoe and 3 bomb runs to Santa Barbara with zero issues until now.

 

[ITRJ]

Gas cap shouldn't cause this issue. Best thing for now is to gather as much info as you can when the fault occurs. Pay attention to outside temp, coolant temp, fuel level, road conditions, type of driving while it occurred etc. you could even get yourself a data recorder. They plug into the obd 2 socket and record ecu data. If a sensor is causing the issue, it may show up in the data.

 

[ITRJ]

Or if you have a handheld scanner that gives you engine data, you could keep that plugged in.

 

[ITRJ]

Do you know what fault was stored before the fuel pump relay was replaced?

 

[burke3265]

Do you know what fault was stored before the fuel pump relay was replaced?

Just looked it up - was a po230 fuel pump relay code. That was the only thing they replaced - nothing else to go on. I'm going to try to have them pull codes again from today's events to see if something else popped up.

Last time (after the replacement) no codes) - so again odd and aggravating.

And now checking Amazon for reader.

 

[LandCruiserPhil]

Having been there without a gas cap or a bad cap you will get codes but it will run perfect.

IIRC there is a TSB on a similar problem and replacing the crank sensor was the fix.

 

[ITRJ]

Just looked it up - was a po230 fuel pump relay code. That was the only thing they replaced - nothing else to go on. I'm going to try to have them pull codes again from today's events to see if something else popped up.

Last time (after the replacement) no codes) - so again odd and aggravating.

And now checking Amazon for reader.

Buy one that will do live data if you can. You don't have to spend a fortune to get that feature and definitely worth it. Often faulty parts won't set a fault code but might be obvious in the data, such as a coolant temp sensor that's reading -40 degrees.

 

[ITRJ]

Having been there without a gas cap or a bad cap you will get codes but it will run perfect.

IIRC there is a TSB on a similar problem and replacing the crank sensor was the fix.

That could definitely cause this issue. Good to know.

 

[burke3265]

So wanted to come back and give an update.

I've screwed on my fuel cap (one click kind) extra hard and have not had another episode in about 500 miles (about two tanks) don't you just love the V8 mileage...

Will be replacing the cap shortly, it never threw another code and my mechanic was baffled but happy it stopped what it was doing.

So for others running across similar issue check the cap, give it extra hard turn (past one click) and see if that makes a difference. Will finish up with a final update when I get the new cap (or knock on wood) the problem returns.

Cheers all and happy Friday.

 

[burke3265]

So one last update.

Wife took truck to take daughter back to school. On the inevitable fill up she couldn't get the gas cap off. Neither could the first guy she asked to help. The second guy couldn't either but had a wrench. They managed to get it off and all was well.

Had her stop by a Toyota shop close to school to get a new cap, parts is parts right? They asked/told her to go to the Lexus dealership.

They couldn't have been nicer, replaced the cap and she made the entire round trip without any issues.

My mechanic remains stumped, so I'll ask the question again, could a faulty gas cap do this?

Regardless I'm happy and hope this episode maybe helps someone else - even if it's divergent from the norm.

Take care all.

 

[1meancruiser]

Guys, I had this exact situation on my 06. It lasted for two years and I replace one cat, a cam position sensor and another sensor (I forget the name) all as Toyota service bulletins and under warranty.

Turned out the problem was that for all 100's up to and including the 2006 the same fuel pump was used. However, for the VVTI engine, that fuel pump was not sufficient and when used extensively in high heat caused overheating. In 2nd half of 2006 and through end of 2007 production a new pump was issued. I replaced With a 2007 fuel pump (different part number then pre 2006 pumps) and issue has not appeared in 2 years including a recent trip to Yosemite, 90 degree temps with 8 people in the car driving 2hours daily.

To summarize, if you have a 2006 LC 100, it's likely you have a overheating fuel pump and need to replace it with the 2007 fuel pump. the part numbers for the different fuel pumps are in a thread I posted a few years back, I can try to track it down if you really need me to?

 

[burke3265]

I have not heard this before but we had a rash of 105 degree days and I too was driving back from Yosemite through the very hot valley when this started for me initially. A summer time gremlin perhaps? I will keep this fuel pump replacement idea in mind - I will check for your previous post, assuming the 07 pump is a fit for existing tank? did it ever throw any codes for you before you replaced it?

Thanks for the reply

 

[ITRJ]

I'd say the tank isn't being vented (air being allowed into the tank as fuel is removed) so as the fuel is used up, a vacuum is being created in the tank. That would make the gas cap difficult to remove, and also cause stalling.

 

[1meancruiser]

I have not heard this before but we had a rash of 105 degree days and I too was driving back from Yosemite through the very hot valley when this started for me initially. A summer time gremlin perhaps? I will keep this fuel pump replacement idea in mind - I will check for your previous post, assuming the 07 pump is a fit for existing tank? did it ever throw any codes for you before you replaced it?

Thanks for the reply

from what my mechanic told me, I don't believe fitting 07 pump was any different then the 06. It's just a part number difference, I think it's a very similar pump. Initially it did not throw any codes, but after being on a long trail and in hot weather, I recall being really irritated and I continue to restart the car even though it needed some time for cooling. My restarts ultimately ended up throwing some codes for lean bank for lack of fuel to the engine.

a couple of threads for your review.

Hard starting in extreme heat conditions

Little disappointed