Tacoma crank/hard start problem (only when hot)

I have a 2012 2.7 4x4 tacoma and am having problems with the engine now that it's getting hot(doesn't happen when cold). It cranks weird when it's hot outside and of course won't do this when I get to the dealer to complain about the issue. I have a video linked to the crank problem. If anyone knows what the problem is please let me know. This seams unacceptable for a 2 year old truck. At first I thought it might be the starter or fuel pump? But the odd thing is that it only happens when its hot outside (low 90's when the video was taken), and if I shut her off and fire her back up she'll crank and turn over normally. It almost sounds as if the ecu isn't calibrating the fuel/air mixture properly and it choking out right before it turns over, but idk. Video of the problem below. BTW it sometimes cranks even longer than the video if it's in the upper 90's and very humid.

Update in post #10


https://www.youtube.com/watch?v=lqRs1oEDdAg

 

Yep, mine does it once in a while too but mine happens when there's major drop in the temperature normally. I've seen it complained about on this forum several times. I have seen at least one person report that the problem never happened again after they changed their spark plugs. I'm going to be doing that soon so we'll see if it goes away. I don't think it's a major issue, just annoying. Looks bad when you're in a parking lot and your fairly new truck doesn't start right up.

 

You've got a V6, he has the 4 cylinder.

 

Still the same problem.

 

You said your problem was with drops in temperature and his is when the temp is over 90 degrees.

 

I'm going to take a few wild guesses here since the dealer did not see anything .....

1.) what was your level of fuel in the tank when this happens??? Any level or just a specific level (i.e., Near/at full )?

2.) From the video it sounds like it starts right up then dies out from lack of fuel .... Prior to F. Injection this would be a vapor lock (hot gas line turning to vapor and not pumping properly .... or a few other things. As for this problem .... Try loosening your gas cap before starting the engine (probably will do nothing but I'd try it.).

3.) Change your fuel filter and have the fuel pump pressure checked....

4.) Has the engine been running in the previous hour before this happens?? (engine still hot?)

5.) (a Real long shot) ... I realize that the pump is now in the tank - but when its' hot out and the engine is also hot - and it sits for a while - the fuel In the lines near the engine may be also be getting to a vapor condition. The Pump and ejectors will overcome this - but - it may take a second or two before it does and causes a rough start up condition. You could try - if possible - to use a temp gun to check for hot spots on the fuel lines near the engine/exhaust.

Like I said - Just trying to help .... Probably not much more than a shot in the dark ....

 

The 1st gen 2.7s have a huge thread about this with no solution found. Seems most just run it as is. Will be interesting to see if the dealer finds the issue and if it's the same issue on the 1st gens.

 

1. Video was taken with about a 1/3 of a tank of fuel
2. I will try and report back
3. I will request the dealer to take a look at the fuel pump and replace filter (truck is still under warranty)
4. No the engine is cold (truck has been sitting shut off for hours outside), but the ambient temperature is in the low 90's when this happens. However, when the ambient temperature temperature is cool and the engine is cold (i.e. low 70's when I wake up to leave) it starts up fine.
5. Don't think that's the problem since this happens when the engine is cold, but ambient temperature is hot. Also i don't have a temp gun.

 

Up here in the northern parts of the US we have a minor issue with old outboard motors. In summary ... The prop screw pitch is, usually, matched to the high end RPM of the boat/engine. This gives maximum HP at max speed per the MFG specs. Remember that outboards have no change up/down gears and must run from idle to max rpm in one gear.

Now, There is a difference between Summer Horse Power and the rest of the year. When mid summer occurs, the Air thins ever so slightly (as it expands when heated there is less air/oxygen molecules per same volume). Also there is the effect of much higher moisture in a set volume of Summer air - further reducing the amount of oxygen for same volume during the winter. We can compensate for this on old outboards, somewhat, by changing the prop to lower pitch prop which allows the RPM to increase back to the maximum RPM at full throttle. This does not make up for lost HP but does help correct to keep available power at full RPM.

With that said (and if you have not fallen asleep reading this ...) I'm wondering if the engine computer is not sensing the higher air temp properly (and therefore higher humidity and thinner air) when it first starts - with a cold engine and hot/humid air.

As to what causes this (i.e. computer programming, temp sensor/calibration, MAF sensor, etc.) I'm not sure. As a possible test, try starting the truck when the engine is cold but the air temp is high - as when you normally see the problem ..... but first remove the air filter. This "might" affect the air flow and MAFS slightly and may make the problem better - or worse, but at least you may get a clue if this is right direction to proceed with at the dealer ..... To summarize what I said is the I think the Engine is getting a little to much fuel for the thinner summer air at first start.

Again ... this is a shot in the dark and just trying to help .....

 

A buddy recommended that filled her up with premium(93) octane to "clean the engine." I thought it would be a waste of money, but damn, she fired up perfectly the past 2 days in 95 degree heat. But i don't understand why it was cranking funny of 87 octane but working with 93. The 2.7 isn't designed for premium unless i'm missing something.

 

That's Great news.... I'd also be interested in finding out if you only had to use 1 tank or and it goes away when / if you switching back to regular fuel??

 

Bad gas?

 

My truck does the same exact thing... My truck did it today.

V6 Auto
Always filled with premium fuel.
I always fill tank at half empty.
It doesn't happen often and it starts up fine at the second attempt.
Temperature doesn't seem to be a factor (in my case) since it even does it after sitting for more than a few hours and has done it in every temp range of the seasons.

I can't recreate the problem and it's so random (maybe once every couple dozen starts or more).... so I haven't taken it to the dealer knowing they'll say they can't find anything wrong.

 

nother v6 here, but mine only does it when I stall it out on the trail. results in long crank/ fail to start on first attempt

maybe some of the more forward thinkers can use that toward a conclusion in regards to fuel/ ign problems

 

My truck does it in during the winter too, so I'm not sure if it's just a cold engine with hot ambient air as with the OP. My engine sounds the same and does the same thing at the first attempt as the OPs, so I'm curious if it's the ECU... Your thought process with the temp sensor calibrations being off or misreading at that moment seem logical (it may explain the randomness of it happening to me).

 

I'll running a bottle of chevron branded fuel system cleaner when this tank has about a 1/3 of fuel left and filli up the rest of the tank with quality 89 from chevron. I think it might have been that cheap Walmart and samsclub gas i've been been using since i first bought my truck 2 years ago, and that's what fouled up the fuel lines and system. But this is also speculation. Hopefully my premium fill up wan't a fluke. I'll report back with the results.