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hi , i have a dakota 2009 6 speed manual transmission 3.7l.the problem with the truck is that it seems to misfire on one cylinder from idle to 2200rpm.the check engine light comes on . when tested with a computer it says #1 cyl. misfiring. i replaced all spark plug , all coils and put in new ign wires.still the same .above 2200 rpm it works ok if i m not pulling a 3500 lbs trailer. in that case i have seen sluggish engine up to 3000rpm in any gear.i had it floored in 5th gear and speed was not more than 90kph. and suddently it came back on all cyl.
i noticed that to avoid the misfiring i must depress the gas pedal very slowly from idle up to 2200rpm. i always have to downshift so the rpm is above 2200 rpm to avoid the situation. im in montreal,so when temp is minus 5 c or colder ,it works good until eng temp rises to normal operating temp.whats wrong with that truck? thks in advance for your advice
 

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Maybe #1 injector leaking/not shutting off fully? When you get the engine to higher rpm, depending on the load, it needs the additional fuel the injector is putting in. Have the fuel trims checked (real time) with a scan tool and see if the engine is really rich at low rpm and becomes less rich as rpms come up (watch the TOTAL of the short term (STFT) and the long term (LTFT) fuel trims). I suspect your engine is set up with both bank 1 and bank 2 O2 sensors, so whichever bank has #1 cylinder would show rich if that injector is leaking.

Just a shot in the dark. But a starting point.
 
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