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I have a 97 F150 with 5.4 Triton. It only has 75,000 miles and has been serviced regularly. A few months ago it started running rough while driving and also at stop lights it would idle up & down. I replaced the MAF sensor and the idle up & down stopped, however I still have hesitation and roughness under load (accelerating, uphill, etc.). It never threw an engine code until I pulled my boat. I had it scanned and the code was P1131 (insufficient mixture, O2s 1/1, lean. I thought maybe I forgot to erase the old code after the MAF sensor replacement, so I disconeced the battery and cleared this code. It still runs rough under load. I have checked the air filter/canister for debris, all vacuum lines & O2 sensor and all is fine. Someone mentioned a bad coil pack, but said that will always throw a misfire code, which I don't have.
Any help would be great. I fear towing my boat since it runs so much worse under that load. I would hate to get stuck on the boat ramp and not able to pull out of the water!!!