Toyota Tundra Discussion Forum banner

2012 CM 5.7 Flex 4x4 rough cold starts solved

272K views 975 replies 117 participants last post by  Supernova54 
#1 ·
Took my ride in for its first dealeer service at 5K miles. Also reported that I was experiencing rough starts, especially on cold mornings. Service tech didn't notice anything. I told the service manager he wouldn't have, because he took the truck right back after I parked it.

Luckily, it had been sitting about 4 hours when I went to pick it up. I got the service manager, who in turn got his shop formeman. After I described the issue, he asked if I had the Flex Fuel engine. When I informed him I did he retrieved his computer and hooked it up to my truck.

He said he has seen a 10 Flex Fuel 5.7's with the same issue now. The Alcohol Sensing Unit was detecting high levels of alcohol, thinking I was running E85 through the system. The truck computers were running the E85 firing program, and it was bogging down my engine. He reset it, and stated he has only had two of the prior trucks return for similar problems.

Fixing this also made my truck run noticeably stronger and smoother. I never quite felt that I was getting all 381 HP out of the truck, now I know why. I have all 381 ponies kicking now, and I love the truck even more than I did when it was being restricted.

Kudos to Price LeBlanc Toyota for taking the time to listen to their customers and going the extra mile to resolve it. Shop foreman was going to submit a report to Toyota.
 
See less See more
#3 ·
Huge thanks to Stompinstu for the information...
I explained the issue to my service advisor on both of my first two visits to the dealer for this problem and both times he had no idea and basically tried to tell me everything was fine.
Well on visit #3 after finding this post and specifically requesting they look at the fuel system reading in the ecu to check if the engine was firing on the ethanol program, they find exactly what Stompinstu had described. I just picked it up so time will tell if the re calibration sticks but I am happy that I found the problem, with the help of this site of course.
Service adviser did say Toyota is aware of the issue and is working on a permanent solution, for now they just re calibrate the settings and tell you not to run with too little gas in the tank. I usually don't let it go below 1/4 but it was on that line today so I'm guessing he just assumed I run on fumes all the time.
If u have a flex fuel 5.7 with a good battery and a strange slow start, this is probably your problem.
 
#4 ·
Ah, so this isn't something that will resolve itself?

I usually park in a garage where it won't get below freezing. But the other day I went to visit my sister in St. Paul and it got down to well below zero the first night and was -2 when I went to start it the next morning. Almost sounded like it wasn't going to stay lit. Warmed up a bit after that 1st night and started it while it was in the low 20s rest of the trip and still stalled/sputtered for a second or two first cold start of the day.

My Tahoe with 200,000+ miles will do that when it's that cold outside but didn't think this truck should (~10,000 miles). Will have to get it checked out.
 
#12 ·
FYI this is not temperature related. It's an ECM issue with FlexFuel vehicles only.

Just took mine back, again, to be reset. Second time. This time I was told to not lay into the throttle very heavy until 15-20 miles after fueling.
 
#13 ·
It does not run leaner or richer....it just runs worse. The program for E85 has different timing altogether to account for the different flash point of E85 fuel.

I'm questioning if I am damaging my engine due to this.
 
#6 ·
Im not sure if it would run lean/rich, or if this issue mostly effects startup and once the engine gets up to temp the ecu reverts to the correct program. Outside temp does seem to make the issue more obvious but Im in hot ass Houston TX and its been in the 70s while Im dealing with this crap.
Just take it in and ask them to check the calibration in the fuel system when its cold, you may have to leave it there for a few hours if your dealer needs as much assistance as mine did to prove it to them. Then your on record for taking it in for this and if anything negative does happen you will be covered. Call Toyota Customer Care also so we can put as much pressure on them to crack the code and find a fix.
 
#7 ·
...this issue mostly effects startup and once the engine gets up to temp the ecu reverts to the correct program. Outside temp does seem to make the issue more obvious...
Just take it in and ask them to check the calibration in the fuel system when its cold, you may have to leave it there for a few hours if your dealer needs as much assistance as mine did to prove it to them. Then your on record for taking it in for this and if anything negative does happen you will be covered. Call Toyota Customer Care also so we can put as much pressure on them to crack the code and find a fix.
Right, and as it's not that cold where I live (but where I travel often) my dealership is like "we don't have that problem here." To that I retort, I'm here and I'm having a problem with the truck I bought from you. There response is a non-emphatic 'oh'. So we'll see.

I had to explain to the guy it would take less than a minute to plug his machine in and see what the truck is running (an E85 program, etc). I'm just worried if it's warmed up from my driving there it won't say anything, they'll say I'm crazy, and I'll be back to square one.

Enter: calling Toyota Customer Care like you said. Just have to see I suppose.
 
#8 ·
Called Toyota Support at 1-800-331-4331 and they had no clue what I was talking about; never heard of it.

Went by the dealer and they did what everyone else is saying (flashed the ECU back to normal or whatever). Said it was in E85 mode. Said they've had 1 other truck in for this.

Now the problem is it's pretty much done getting real cold here for the year so I won't be able to simply catch it if it reverts back to E85 mode through rough cold starts. Asked the dealer what the next step is because of this and just got a blank stare. (I swear mechanics smoke weed daily before opening all local shops around here)

They said their techs had to call their national tech hotline the first time they came across this. So I guess I'll call the 800# above back and see if they can talk to that part of Toyota and let me know if a fix is ever come up with. Can't imagine it's 100% good to be running in E85 mode with normal/'E90' gas.
 
#755 ·
If I'm not mistaken, E85 isnt 15% ethanol, it's 85% ethanol. In Michigan, we get 10% Ethanol in everything. Pure gas is available but hard to come by. So pump gas is E10, not E90. Not to split hairs, just thought I'd try and help clear that up. I hate the fact that all V8's in this region are FFV. It will be a hassle to add the TRD Blower (Sparks says they can do it and keep the warranty intact). And corn fuel is dollar-negative. Subsidies will never get that pig to fly. We should be filling the rural southeast US with sugar cane if we wanna grow fuel. Plus, E85 burns dirty. This is my second Gen 2 Tundra and neither has ever seen a drop of E85.
 
  • Like
Reactions: Mr. Creosote
#10 ·
After whatever it is the dealership did to it, mine still sucks...moved to a new place and started parking outside more (vs. garage). It only gets into the 30's currently but every morning it stumbles a bit on start up.

To the 'untrained' (un-anal) ear it's nothing. But it's not something a truck with less than 200,000+ miles on it should be doing in my experience/opinion.

Other issue is I've moved over an hour away from the nearest dealership. So that should make things funner. At least it's a different dealership...
 
#11 ·
Mine still does it also. I'm going back to get my 15k oil change in a few days, ill see if they can do the refresh again. I'm thinking the tech working on my truck did the reset after he started it, which would probably negate the reset. The fact that most people have had success and others have not makes me think some techs are performing this reset incorrectly. I'm going to strongly request they let the truck get cold (min 4 hours) and perform the reset on fuel density prior to turning the key.
I have no guarantee this will be the trick but its worth a try.
 
#16 ·
Stu,

Sorry to hear you had to go back, Ive been holding off til my oil change is due and since I haven't been on the road much, its been dragging on and irritating me more and more.
Id bet there are many many Tundra owners who have this issue and maybe dont notice or think the battery is prematurely going out.
If a fix, one way or another, isnt found very soon I may try to sell the truck or file a lemon law form to have toyota buy it back. You cant sell a flex fuel truck if the damn thing cant tell the difference between the 2 fuel types.
Lets keep each other up on any news related to this problem.

Before I saw your post yesterday, I emailed Eric at Price LeBlanc asking him for the step by step details on the proper reset procedure so I can tell my guy. Obviously, yours didnt stick either so maybe the reset really is a temp fix.
 
#19 ·
I'm having this same exact issue with a different problem. My truck starts fine but runs like crap. Engine miss in every gear now. Dealer re-flashed a few weeks ago and it has been running fine until yesterday. He told me he would keep re-flashing it until Toyota releases the new program. So, I'm in the same boat as you guys.
 
#21 ·
I called Toyota Corp customer hotline office and still no news on when or if. From now on I will never buy another FF vehicle, if any techs out there read this, please keep us in the loop on updates.
I can hold tight for.... who knows how long to wait for a fix, sell the truck with the problem, or go through arbitration with Toyota and see what the mediator decides.
5.7 power is no more, I feel like Im driving my buddys 4.6 Ferd
 
#22 ·
Moved and using a new dealer. Called the new dealer to make sure they knew what I was even talking about before I drive out to them to get 'flashed' again.

Looked up my VIN and stated they could see where the other dealer noted I came in but said there were no notations stating any work was done. So who knows. Maybe they never flashed mine in the first place. A-holes.

Getting it flashed tomorrow...

Edit: stated the other trucks they've flashed have not been back with the issue.
 
#23 ·
Latitude, are they actually re-flashing or resetting? I went back to my dealer today and asked if I could hang with the tech to see what is going on. He hooked it up to techstream and sure enough the truck is telling the comp that there is 50% alcohol density in the fuel. He reset it as he did last time but last time it made the issue go away for a while. It didn't clear it this time so I'm back to square one. He did say yota is supposed to be releasing the reprogram for the ffv's anytime now. So until then, I hate to say it but I'm pretty dissatisfied with my truck. It's running like crap right now missing/hesitating in every gear. I put a call in to toyo corporate after leaving the dealer (dealer is doing all that they can and they are good people) and I'm supposed to hear back from them next week. The two people I spoke with knew nothing of the issue or the supposed reprogram that is coming.

If any of you guys go back to a dealer please keep us posted on what they say and do.
I'm not putting anymore money in my truck util this is fixed. If it isn't fixed in a moth or so I guess I'll have to sell it and go to another brand.
 
#24 · (Edited)
Not sure if it was re-flashed or reset, etc. I'll ask to go back with them tomorrow to see exactly what they do.

New dealer sounds more patient. Last dealer was at least as competent. But the one I'm going to tomorrow serves a micropolitan area of less than 80,000 (and I'm having to drive almost an hour to get there...tells you how BFE I moved lol). So their service department doesn't exactly get swamped like the last dealership I was using. Hopefully get more details vs. an out the door ASAP treatment.

All I know is back in the day I wouldn't drive a truck ~15,000 miles with the timing retarded (assuming that's what's going on) and think good (or neutral) things would come of it later down the road. So trading it does sound tempting.

Going to law school to be an attorney for stuff like this would have been nice. Not that I would want to be a full-time attorney or anything. Just to be able to get class-action style things off the ground for occasional crap like this and know what you're doing. Just not worth the time/effort to find an attorney to deal with it at this rate. Just annoying the dealers don't know anything and corporate is playing dumb.

Also, going to be annoying if this 'fixes' it (mine only seems to be noticeable when below 40 outside and it's about to heat up for the rest of the spring/summer) just to find out it was potentially doing this all summer when it starts being screwy again next fall/winter.
 
#26 ·
It should be running crazy rich. E85 has less energy in it so it takes more of it to do the same job. If it thinks you have e85 in it, it should try and add extra fuel to the system. I bet your MPG sucked too.
 
  • Like
Reactions: Powertechn2
#27 ·
Right. So now enters the question of if you want a truck that now potentially has 15,000 miles of random carbon deposits due to all that rich running.

I asked earlier in the thread if it would run richer and was told no. Still have a new engine running funky timing that begs the same question: do you want to try to put 200,000+ miles on the thing
 
#28 ·
Lat, please re-confirm with me tomorrow if they actually REFLASH the truck or just reset the ECU as I watched the tech do with mine today. Maybe you could get them to let you sit with the tech like they did me today. Please also let me know if this solves your issue. Having it re-set again today still did nothing for mine. It's running like crap, I don't know what to do other than hang my head right now.
 
#29 ·
Will do. There is a ghetto gas station selling 'no ethanol' fuel here.

I'm also tempted to get pretty empty (pretty much am already) and fill up with that before tomorrow and just run ethanol free until a fix comes out. Maybe staying away from the 'normal' 10% stuff will help keep the thing from tripping again.
 
#31 · (Edited)
Apparently it's a fuel gauge reinitialization flash (I think; forgot the exact term). Apparently the issue pops up when you refill with gas and subsequently jump back on the interstate and stand on the accelerator. Or refil before taking off on a mountain drive requiring a lot of acceleration. Etc.

When you refil with gas, the fuel gauge takes off, and that signals to the computer to figure what you just put in the tank. So if you are accelerating back onto the interstate, etc (accelerating a lot during this 'discovery' process) it sees the mixture is rich (due to your keeping the accelrator open more than normal (not my normal and I guess why I had it return)) so the computer derives you've got E85. So it's too stupid to know you're running rich due to accelerating vs a new tank full of E85.

Therefore, for the rest of the tank you've got the injectors/computer trying to dump 2x the needed gas (as you're not running E85) into the engine until you flash it again. Piece of shit.

Also, disconnecting the battery resets vs flashes anything. The tech im working with seems very disinterested in this as he's not going to do it
 
#32 ·
Man it sucks to hear that. I was hoping you'd find someone who could finally provide a permanent solution to the problem. For some reason lol, I just feel like saying we're all f'ed lol (as far as the guys who have this issue).

Toyo corporate is supposed to get back to me Monday. They told me the other day that they'd never heard of the problem which leads me to believe that they really aren't going to be releasing a re-program (like my dealer said) anytime soon if they don't even know about the problem.
 
#33 ·
Theyve heard of it because I called and told them about it a while back. But they told me they hadnt heard of it then when i called. So bluh. Guess that's their token response.

Seems like it's only an issue on startup when it tries to flood it. Once running as someone else already stated other parts of the engine 'fix' the mixture. Whether it tries flooding it/over enriching it when rapid acceleator movements are made or while rapidly accelorating seems to still be open for depate.

No word on if it affects the timing.
 
#117 ·
It doesn't get "fixed" while running. You're timing stays tuned to the "grass gas" setting the whole time. This is why I am worried about permanent damage to my engine.
 
  • Like
Reactions: Dixon Cider
#34 ·
My 2012 Double Cab ( 5.7L) was hard to start ( when cold ) for a while now. I took it to Hendricks Toyota in Apex NC and they re-flashed the ECU. They told me the gas / ethanol mixture was confusing the Flex Fuel system ( whatever that means) and that there was a code: 1604.

Now it starts very quickly and runs well

Let's hope it stays that way .............
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top