Thermostat stuck open?

Did you come across that thread?

 

^^^^ This, do a search looking for the thread about thermostat problems. It seems if the stat is faulty the engine may not come up to optimal running temp the ECU see's this as a cold motor on a cold day and richens the fuel mixture similar idea to the days of carbs and chokes.

 

Could the opposite occur? Thermostat stuck closed would cause too lean of a mixture for it to start in extreme cold?
I ask because last week it got down to -20F here and the FJ would turn over fine just wouldn't start. I tried about 12 times until the battery started to sound weak.
It eventually started when it got up to 12F.

 

That doesn't jive to me for the following. The engine is already cold so the ECU should not sense a stuck closed thermostat as an opportunity to lean the mixture. If anything, it should see it as an opportunity to enrich the mixture for help getting started.

 

Only hard to start when it got very cold but starts fine in warmer temps???....The thermostat will not have any direct effect on a cold day start. The normal position for the thermostat is closed it will stay that way until the coolant temperature rises above approx 180*F.... Not starting in extreme temps could be as basic as water in the gas, old gas , snow plugged exhaust tail pipe, or one thing that used to be a common problem was opening or pumping the throttle while turning over the motor. I have not looked in to the FJ throttle system to see if this is still a issue but the advise is the same you don't need to apply throttle while trying to start the motor. How clean is your air cleaner?? and air sensor. With your truck starting when it warmed up we know you have compression and spark so the problem is going to be... air or fuel. Water in the gas can be treated by adding about a pint of iso Alcohol to a tank of gas. Just a few thoughts .....Pretty hard to know what went wrong with the truck running again.:cheers:

 

Starts great in warm temps. It seems the lower the temps the more times I have to turn it over to start. We're talking under 15F it begins to require more than one crank.
Maybe water in the gas. Air filter is fairly clean.

 

Winter gas blend sucks!
Burns a lot faster.

 

The engine wouldn't burn seven gallons of gas in forty miles if the it was stone cold the whole time. And it's not bad gas - because gas that contaminated - or badly mixed with winter additives - would cause noticeable problems in performance.

A worst-case:

OP, check your oil. If the dipstick reads high, that's where your gas is going - cylinder wash down into the sump, and then evaporation as it's sucked through the oil galleries and bearings. It can be caused by injector leaks or malfunctions. If so - your oil is contaminated and the vehicle should not be driven until the problem is fixed and the oil is changed.

 

Agreed, this kind of gas consumption does not fit with bad gas no matter how bad !! For clarity the bad gas suggestion was directed to the hard starting question posted by "Despotes".... Regarding the fuel consumption to be honest a claim of this kind of extreme poor milage in combination with saying the "engine runs good , sounds good, has plenty of get up and go" do not fit on the same scale of possibility. Your thought of a problem with wash down and injector failure is Excellent but even at that I would think this truck should be hard starting, if at all and running like a bag of garbage at low speed/RPM for sure and the exhaust should be soaked and likely puking out black smoke.... Good suggestion to check his oil level, if your correct the oil may also smell like gas and yes if his oil is gas soaked stop driving this truck.

 

Definitely a worst case....

 

The FJ sucks gas better than it off roads. And she off roads fairly well.

 

My scangauge has been giving me 20-24mpg highway...


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Maybe you got a leak and if you park your rig outside you might not be smelling it.

 

I thought I got bad mileage.

 

I agree with John. If there was leak down (at this level), the engine performance would be noticeably worse than normal.

I would be checking fuel lines.