Surging during light to moderate acceleration

I'd think it would kick a check engine light though. I looked at the gas cap and didn't see anything out of the ordinary. I suppose it could be something like a vent in the cap. I'd definitely try that before fuel pump replacement. Fuel pump for a flex fuel truck is right around $650.

 

Don’t you just hate it when the answer isn’t clear as day?

 

If it didn't come and go I'd not be so confused. I'm an ASE certified master tech in heavy duty diesel trucks. But I have all the software and needed diagnostic equipment supplied by my employer. This flex fuel stuff is all new to me. And gas is very different compared to diesel. If I could just say something that I know 100% to be true I'd go in that direction. It did rain yesterday and this morning. And the surging is back and it had been dry the past few days. But I also put gas in it and then boom it changed. It's either something getting wet or something that changes when I get gas. I think .

 

Don’t know if I said this before, but it sounds like a fueling issue in one way or another. Maybe something to do with the charcoal canister evap bullshit.

 

I agree totally on it being fuel related. But I'd like to see concrete evidence before I plunge into a fuel pump.

 

Maybe a shot in the dark, but the next time that you have a stretch of dry days and no surging, see if you can give the engine compartment a light spray with a garden hose like you're just giving it a rinse to get rid of dust. It's free, you'll just be at the mercy of trying to time it with the weather. Trying to monitor the fuel pressure while it's being driven and as you mentioned, the alcohol density readings (and resetting them to zero) are the other things I would be curious about.

 

Ordering a obd2 Bluetooth device right now. I'm gonna check into torque pro and see if it will monitor the alcohol density and fuel pressure. I know there is some reserve fuel that sits in the tank even when it shows very little fuel. I ran it down pretty low in order to get as much ethanol free gas in it as I could yesterday. But it should read at or near zero right now?

 

I think it's supposed to be dry around Tuesday. But I'm sure it's not gonna completely dry out for a few days .

 

I drove it a few miles yesterday before I got gas and it was raining pretty hard. Around 4 miles on the interstate before I got to the gas station that has ethanol free gas. Drove it probably 15 miles after getting gas in a steady rain. Never noticed the surge. Truck sit over night till this morning. Been surging all day.

 

Dang man, this is really befuddling. I suppose that given what you experienced yesterday, I might lean toward what I mentioned. Getting information on what the fuel pressure and ethanol readings are. I have a Haynes manual that gives fuel pressure info for the 3UR-FBE (Flex Fuel Vehicle) of:
Fuel pressure switching valve is OFF.................................................39.2-47.9 psi
Fuel pressure switching valve is ON .................................................53.7-62.4 psi
Residual fuel system pressure (five minutes after engine turned off).....21 psi

 

Try putting a can of seafoam in your gas tank it will help if water is in the fuel

 

Here's another thought. Water in the gas. When the gas settles to the bottom from sitting it allows the gas and water to separate. When gas is put in it stirs up the water and it is picked up and sent to the engine. Can of seafoam is safe for flex fuel?

 

I just ordered a Bluetooth obd2 adapter. $22 on eBay. A guy at work uses one and has great things to say about it. Bafx I believe is the name of it. Great reviews and works well with the torque app on Android. Crazy that a $22 adapter and a $5 app will do more than many obd2 scanners that cost much more. I guess I could also use a fuel pressure gauge off the fuel rails and attach that gauge to the windsheild to be viewed while driving. I want to see that fuel pressure while driving and making it surge. I only had a limited amount of time when I had that Modis hooked up and I had my friend watching the screen while I drove. I want to log the pressures while I drive and view them myself when I get back home.

 

Yes

 

Check out this post.

 

The spitting and sputtering under a load has my attention .

 

So today it looks like it's gonna be a no surging day. Still rainy and cloudy with plenty of water on the roads. Here's what I'm thinking is going on. This is yet another guess somewhat. I started the truck this morning and let it warm up while I got the kids ready for school. Same gas none has been added. Not sure if I just ran and jumped in the truck yesterday morning or let it idle till warm. I believe the pcm or ecm or whatever ECU is learning the alcohol density is getting it wrong. Maybe the learn procedure only happens when the truck has sit cold? And then when it's warming up the calculations are made. And maybe it is flat out getting that reading wrong after a fuel up? It would explain it all. I can't wait to see if my findings are correct when I get that obd2 adapter. Maybe it's been doing this since I got it but the next morning after fueling up it's been cold enough to let the truck idle long enough to learn the new gas and make it's adjustment correctly. I feel like I'm on to something. The fix would then be to let the truck idle till warm the following day after getting fuel. Wouldn't that be nice!

 

Let us know.

 

OBD adapter will be here tomorrow according to the USPS tracking. I'll be fueling up tomorrow as well. Hasn't surged the past few days. Bet the following day it starts again. At least I'd have something I can say for sure if it does. It begins the day after fueling up. Also downloaded torque pro for $5 and it shows the ethanol % but hopefully it will be accurate to what the ECU sees. I'll have plenty to update tomorrow. And the following day. I have a can of seafoam ready to go in as well. Want to wait till I have plenty in the tank though. Also want to see what the alcohol density reads before and after fueling. If this ends up being something stupidly simple I'll be mad and happy all at the same time.

 

Ethanol percentage reads 5.9% with ethanol free gas that was last used. Fueled up with the regular e10 gas and it's currently at 4.3%. Bet the truck surges tomorrow and that percentage is high. It's a possibility anyways. There was still roughly 1/8th tank left plus reserve so I can't say how accurate this reading is yet. When hooked to the Modis it was reading 14 point something. And it was surging.

 

Just gassed up again. 91 octane E10. Ethanol percentage shows 10.2%. The ethanol percentage did not change instantly after getting gas. When the miles to empty range updated so did the ethanol reading. Let's see if it surges. And see if this gas stations ethanol is actually over 10%.

 

Been 7 days with no surge felt whatsoever. It's rained. Been cold etc etc. Not sure what changed all of a sudden. I've done nothing different other than plug in a scan tool and read the ethanol reading. Maybe I scared it. It knew I was onto it and it knew it better act right before it got parts changed.

 

@Coldjustin have you experienced this again yet? my 2011 has started to do the same thing. I've hooked up an OBD2 scanner and I have read 64% ethanol. I only gas up with 87oct

 

My truck mysteriously stopped the surging. I never ran any seafoam through it hoping to see the ethanol % over 14 and since I got the OBD scanner I've not seen over 10. Gassed up today and it was at 7%. Does your truck have any problem starting?

 

Our 2011 models were not included in a recent tsb from Toyota regarding this problem. 2012 and up had the ethanol readings very high and they had a fix for it from what I've gathered. But the dealers wouldn't update our 2011's. My dealership is willing to but I have to show them that it's not reading correctly. I'm gonna say I just got some bad gas and once it ran through it's cleared up.

 

Also I notice you had new exhaust work done. Mine began surging shortly after changing exhaust. If mine would start doing it again I would attempt to locate it. But for now I'm just gonna drive the wheels off of it and monitor the ethanol readings. Let us know what you find. There are several 2011 flex fuels having the same problem.

 

Yea, It did start after I had my exhaust done however there were no issues for about 2 months and now it's doing it (exhaust was done 3 1/2 months ago)

 

btw... no issues starting once I changed the dying battery Only seems to surge around 1700-2300 rpm's

 

That's the same range of rpm my truck was surging. Got gas again today. 7.1% ethanol. Still no surge.

 

Regarding low octane fuel being the possible culprit. These Toyota engines are set up to run on low octane fuel. Running higher octane fuel will not benefit you. I have run several tests on my 5.7 Tundra and fuel economy drops from 17.2 avg with 87 octane down to 16.8 avg with 93 octane.