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Yadkin 08-18-2013 09:55 PM

Code P0302, related to towing?
I picked up a UHaul trailer in Boone, NC (elevation 3300 feet) on Friday afternoon and hauled it empty up to my cabin in the mountains. Lots of long, steep grades and the Jeep handled it well. When I got to my cabin (elevation 4900) I unhooked it to do errands on Saturday morning. On my way back up the mountain (no trailer) the check engine light went on with no EVIC message. When I got to the cabin I parked it, and in the morning checked the oil and all the fluids and everything was fine.

Then I hooked the trailer back on and loaded it up with furniture and drove down the mountain, stopping at home (elevation 800) to spend the night, and then used my reader to find code P0302 "misfire on cylinder #2". There was no misfire on the V6; heck I can tell if there's a misfire on a V8. I reset the code it immediately came back on, and I tried that twice.

The next day I drove it on to Raleigh (elevation 315) with the trailer full of furniture and it ran perfectly, but the engine light on the entire time. I unloaded the furniture in Raleigh then dropped the trailer off at UHaul there. When I restarted to leave UHaul the light turned off after the initial prove-out.

100 miles later, back home and the light never came back on.

All this was on the same tank of gas.

I make these same trips and elevation changes often, about twice/ month on average.

Weird. Any thoughts on what the issue was?

Scottina06 08-18-2013 10:01 PM

Re: Code P0302, related to towing?
gonna need a new head

padgett 08-19-2013 09:14 AM

Re: Code P0302, related to towing?
P030x is set when misfires exceed A Lot. 300 is several cyl, 302 means #2 cyl. This is a common indicator on a 3.6 of the head ailment common to '12s.

I check for misfires every month but sofar is in the 0-2 range.

Yadkin 08-19-2013 09:48 AM

Re: Code P0302, related to towing?
This "common head ailment", is there a service bulletin on it?

Yadkin 08-21-2013 10:29 AM

Re: Code P0302, related to towing?
There must be, since they are changing the cylinder head under warranty, and had all the parts in stock.

padgett 08-21-2013 11:46 AM

Re: Code P0302, related to towing?
CJF% knows about the issue but has avoided releasing a public TSB. It does seem to relate to load, temperature, and gas quality.

If I were towing a load in the hills on a hot day suspect I would use 89 PON

Yadkin 08-21-2013 02:39 PM

Re: Code P0302, related to towing?
The vehicle is rated to tow 5000#, and the trailer weighed a fraction of that. Also, there is nothing in the OM that says to use a higher octane fuel when towing.

I've had no performance problems with this engine.

Maliberti 08-22-2013 09:07 AM

Re: Code P0302, related to towing?
I had the same issue with the CEL. I was not towing.
I also had no performance issue.

Just had the heads replaced under warranty, they had my car for 2 weeks.

I thing I noticed after the new heads was the car does not steam out of exhaust.

This car from day one always had slight steam coming out of exhaust in the morning, regardless of temperature and this would be like this on every cold start. They told me this is normal of all cars, and I too believed them as every car I have owned did this in the morning when it was cold, but this car was doing it regardless of temp and it would last well beyond the warm up period, now its gone.

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