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P0302 code



Has anyone come across this code? Went on a little ride yesterday and about 12 miles in, my first check engine code. Apparently it’s a cylinder 2 misfire. I could hear it knocking and running a little rough for about 10 seconds when I stopped and tilted the bed up. Drove it back to the trailer in limp mode, no knocking, sounded normal other than it being in limp mode. Got home to get it off the trailer and code was gone, running fine. What do you think? Just a fluke? Or something bigger to look into?

here is what I know so far:

82 hours on our defender, 1050 miles.

Running in high when the code came up. About 20 mph on flat ground. 

Fuel was 89 octane and was only about 2 weeks old. Full tank. I’ll be filling with 87 octane “top tier” gas from now on after reading the other thread about knocking and stalling issues. Maybe this could have been my problem?

checked the spark plug wires. Good connections on plug.

Pulled the spark plugs, checked gap .034 on both. Plugs looked good.

I did realize that I hooked my battery up in reverse order from what the manual says after my battery install project. Whoops. Would this cause a misfire code though after 30 minutes of riding? I don’t know. But for the future... disconnect negative before positive and hook up positive before negative. Note taken.

pulled the fuel pump out of the tank. Pump prefilter was a little brown. Very dusty conditions out here in the desert. Bought  some replacements just in case. I’ll change this piece out and post a picture of the old one. Hard to tell if mine is actually clogged or being restrictive to fuel flow. Maybe this was the culprit?


any help is appreciated!


Edited by pmbaseball24
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My SWAG would be fuel with moisture in it, resulting in fuel separation and drop in octane? If the code went away it was a temporary code which can sometimes be reset by letting the vehicle sit or disconnecting the battery for awhile?

As far as fuel octane, I burn 91 Octane no ethanol fuel with no problems so far. The reason for going to 91 no ethanol is that the chance of getting water (condensation) in the fuel is reduced because ethanol tends to adsorb moisture from the air. Even if the fuel sits for awhile it loses octane but attracts less or no moisture. The higher the ethanol blend, the more likely the fuel is to attract moisture and condensation up until the point that you get fuel separation from the ethanol water mixure and corrosion and knocking starts.

I know that from the factory the machines are programmed for 87 Octane as a default because your fuel loses octane while sitting in your tank as well as in the tank at the retailer. The engine is equipped with a knock sensor that will pull timing if it detects detonation. I have never heard of an engine knocking from a fuel with a higher octane because higher octane fuel burns slightly slower and reduces the chance of detonation.

I run 91 octane no ethanol fuel in all the seasonal equipment as well as my boat, sleds, quads, chain saw, weed trimmers etc. not because I get better performance for the extra cost of the fuel but because I don't have to deal with the corrosion in the carburetors from ethanol fuel attracting water and forming the beautiful green slime in the fuel bowl.

I have a tune that runs a bit more timing to try and get a bit more power from the 91 octane no ethanol fuel (also has more energy than 5% ethanol fuel) that you can't get from the stock program. Even with this program the ECM will pull timing just like the stock tune if it detects detonation? JMO🤔

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Thanks for your insight Andy! I may be wrong but I believe the quick trip gas station I fill up at out here in Arizona is “top tier” gasoline which is just an additive package when fuel is ordered, with a maximum of 10% ethanol. I’ll double check that next time I stop by. I would assume with our dry climate out here, the fuel should be less prone to moisture absorption? Maybe that theory is completely wrong, I have no idea.

 When I changed the prefilter on the pump, I didn’t notice any moisture or water in the tank. Keeping my fingers crossed this was just a fluke thing. Thanks again for your help!!  

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