08SuperSierra

Hay everyone so my 08 Sierra with a 5.3 has been throwing a CEL for fuel trim issues 1 code it will say bank 1 Lean and then another time it will read bank 1 system imbalance bank one so my long term fuel trims are around 20% both banks I have looked at the mV for the o2 sensors all read roughly 500-700 mv if you floor it the pre cat 02s will dip to around 40-100mv post cats stay roughly the same I’ve sprayed around the intake and injector area with carb cleaner and water, didn’t get any results leading to leaking gaskets maf was cleaned CEL started appearing when it was around freezing weather, and wouldn’t turn on until it cooled down and re warmed up I don’t know where to even start being I don’t believe it’s a underperforming o2 sensors as it could be a large air leak or a underperforming fuel pump causing a lean issue but it only throws a CEL for bank one?? But both banks at at 20%???

Bob2c what kind of tuner do you have?

Maybe it has had the lifters replaced once twice maybe five times already but I don’t know that. I bought the truck from a ford dealer and the there was nothing on the car fax/ paperwork that was in the glovebox other than accidents yes that’s plural, ( a 4 time hitter) < that’s a funny story, and basic maintenance. Afm has not been tuned out as it still goes into v4 on the dash and there is a auditable exhaust note change. no Signs of failure as it doesn’t click or clack on startup, no useage of oil or misfires. my biggest complainant on the AFM that when it does switch into v4 and you do not cruise on your speed will decreases because the truck isn’t making as much power. Example, going a flat 60 in v8 mode, it switches to v4 and now with the pedal in the same spot your only doing 56 Mph in a near matter of seconds. You than slightly Accelerate To get back to speed at its back into v8, just annoying I've looked into the Range disablers I just haven’t pulled the trigger on one yet.

Hello everyone I’m just sharing my experience with my “lower than normal oil pressure” problem To start out my truck has 190k 2008 5.3 AFM works great no problems So it all started one day in February, I was going out to a hunting spot, going up a gravel road/slight hill with around 6” of snow on top of it. locked in 4 high just banging rev limiter and near red line to get my self out without getting stuck, oil pressure gauge was hitting probably around the “60” mark engine temp got around 220 and tranny 160 so after that on my way home on start up it had around 40psi on the gauge, after briefly warming up ( the oil ) it would rest around 20psi, would barely hit 40psi unless you went WFO or engine was cold. Anyways after doing some research I chalked it up to sludge and garbage got up to the oil pressure sensor and the screen due to the extra oil pressure. So I replaced the sensor and the screen. And the results of that was nothing. Still had the same problem. than I through the oil pressure Relief valve in the oil pan could be stuck open, ( as I read the relief opens about 60 psi on 4th gen Ls engines to reduce the chances of over oiling damage) figuring that was the problem there wouldn’t be much I could do about it. But come today, I changed my oil and filter ( ac delco pf68e? I think *of the top of my head* And semi syn 10-30 ) it’s fixed! oil pressure is 40+ cold, and still 40psi when warm. So in the end CHECK YO OIL FILTER cuz They suck why would gm put such a small filter on it? Hell the oil pan is Deeper than the filter and they could have made a longer filter, I assume it’s gm being cheap and re-using oil filter designs from different platforms. Any one know a bigger oil filter? Or at least longer? or I’m gonna get creative and find a way to make one of my PH8A filters from my stock pile to work.