Q: Truck bogs out under load

asked by on September 26, 2016

I've replaced the plug wires, coil packs, throtle position sensor, fuel pressure sensor, fuel filter, and cleaned the mass airflow sensor, but the truck still bogs under load. I no longer have any codes due to my battery dying but the two codes I remember are p0171 and p0174. If it helps I do have short and long term fuel trim numbers at idle and at 2500 rpm... At idle STFT bank 1 =1.6% -10.2%... Bank2 = -2.3% - -3.9% LTFT Bank 1 = 2.3% - 3.1% Bank 2 = 9.4% - 10.9% and at 2500 rpm STFT Bank 1 = 14.1% - 21.1% Bank 2 = 6.2% - 9.4% and LTFT Bank 1 = 14.8% - 16.4% Bank 2 = 18.8% - 19.5% . I must also mention that my egr valve tube that attaches to the exhaust manifold has completely rusted away. Could that cause lean mixture codes? I look forward to hearing from you soon. Thanks Bruce. P.S note the STFT Bank 2 were both in the negative at idle.

My car has 150000 miles.
My car has an automatic transmission.

First, the EGR tube rusted away will cause excessive air to get into the exhaust and cause the O2 sensors to read erratic. The main reason you most likely have a mass air sensor that is not reading correctly for the altitude you are at. You should check the mass air sensor with the key on and engine off to see if the barometric sensor is reading the correct altitude. If it is reading above 10,000 ft, then replace the mass air sensor. Disconnect the battery for 10 minutes to clear fuel control then road test for problem. If you need a diagnosis, a certified technician from YourMechanic can come to your car’s location to inspect the loss of power and advise you on repair.

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