Venuspie

iTrader: (1)

Had spark knock issues for the past 1000 miles or so. Thought it was bad batch of gas so I ran a second tank from different store. Same. Hear it best when pulling a hill in 6th gear. I switch between e-85 and 87 octane often but have been using 87 for past couple of months.. No real reason, just enjoy the extra pep from e-85 every once in a while. I wonder if the truck thinks I'm running the 105 octane and set timing too high for 87? Any ideas before I enter the dealership woes? Truck has 12k miles. All stock.

kbass24emtp

Have you tried to disconnect the battery for 30 minutes. Turn on you headlights before you disconnect. If it still does it after that, check with your dealer.

Venuspie

iTrader: (1)

I will give it a shot. I've never heard of this before. Why then the headlights on?

Koolponycar

I have a 2012 5.0 fx2 and have had the same issue from time to time. I currently have my first tank of E85 run down to 1/4. I am going to take mine in to the dealer also to see if they can find anything. It does it some times at 1100 rpms in 6th up hills too. This started last year during the winter but not all the time. I tried regapping plugs to .045 and using real gas vs ethanol. Right now not a peep. But still going to take it in, could be knock sensors but there are quite a few that have complained and went to higher octanes but that doesn't always cure it.

kbass24emtp

It drains all the power to the ecm to clear the memory.

papa tiger

Possibly the trip to the dealer will find a bad ethanol test. Disconnect battery for 15 minutes an fill up with 87 octane. Let the O2 tester set Stoic with the PCM. Read your owners manual. Every time you change motor oil do it with a tank of 87 octane to set stoic. If that doesn't do it for you dealer will replace faulty parts.

Venuspie

iTrader: (1)

I'm sorry. Been super busy and haven't had time to respond. I appreciate all the input. I disconnected the battery for about 30-45 and have about a half tank of 87 but that hasn't changed anything. I have appt. for Friday at dealer. I will read the manual before then and see what I can find. I didn't realize that a flex-fuel vehicle needed constant maintenance to help it read the octane correctly.

papa tiger

Full tanks of 87 octane and full tanks of E85 but unfortunately E85 can be all over the place in octane depending on the fuel source. Most don't have to do this, it is just a good way. I suspect you are getting a low grade E85 near 50% alcohol which if you have some 87 in the tank further degrades the percentage. 15 gallons of E85 at say 60% and 11 gallons of 87 octane at say 10%, thing would be like trying to calibrate E30's stoic. Not a OEM recommendation. It should calibrate stoic with more than half a tank if it is pure 87 octane. Going back and forth is possibly UR problem with 1/2 a tank at a time. Not a recommended option but the O2's should be able to set the stoic with the PCM.
Of course you may have a more serious problem. UR dealer will help you.

Koolponycar

Thanks papa tiger. I took my truck in today for the occasional knock described at low rpms. I did have a blend of E85 4 gallons and 100% 87 5 gallons in tank run down to about 80 miles until mt. My truck has never run better than it currently is.I can definitely feel the power difference mixed. I am planning on switching on over to 100% real gas. They checked everything even AFR all looked great. Tech drove it and put it under a load check computer history and codes and found nothing. I looked up Stoic to see that it is the perfect air to fuel mixture for a perfect burn. I have been running the shell 87 and 93 for the past year which has N2 in it correct? I wonder if this has caused some leaner conditions as some research suggest that if too much 02 could be removed also. N2 definitely displaces O2. What do you think?

papa tiger

N2 gasoline additives by the manufactures help clean the cylinder much like some of the fuel additives. Nothing wrong there but keeping the tank fill ratio nearer to either gasoline or E85 would be best. As close to Full Tanks as possible is what I use. Haven't had a problem that a way with 400,000 mile plus of it.
The Manufacturer will frown on a fuel additive in a bottle as it sees damage to the catalyst or turbo as possible.