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I have a 2008 Chevy Impala 3.5. I have a code p0171 system too lean bank 1. I've changed both up/downstream O2 sensors and the MAF. I've also changed the fuel canister and purge valve. I don't know what else to do. My car fills like it's misfiring when driving and makes this weird vibration feeling sometimes when I accelerate from a stop. What could this be from? Please help. Very frustrated!!
There are three o2 sensors on that car which ones did you change with location. What other codes did you have. Do you have a scanner that can look at live data? If so what are the fuel trims at idle, 1500 and 2500 rpm? Does your car have a plastic intake manifold? Are all hose conection rubber fittings in good condition (not cracked or broken)?
I changed both O2, the one on the converter and the one by the engine. All hoses are in good condition. The scanner I have does not have live data unfortunately. I do know that on the freeze frame it was at 608rpm fuel trims long and short were at 29.7 before changing the MAF. Once I changed that they were reading long @ 29 and short @ 5 or less. The only other code I had was a large EVAP leak but that went away once I ch aged the purge and canister and replaced the gas cap. Also, I'm not sure if the manifold is plastic but it probably is the way cars are but these days... Lol.. thanks for the response, hope this info helps some!
What are the fuel trims on bank one at idle on the scan tool?
Do you have any way to smoke the intake and look for leaks on bank one?
If you done try spraying something like carb cleaner/brake clean around the intake gaskets for bank one, see if you can change the way the engine wants to run.
It seems like you could have a vacuum leak if it only happens at a stop.
So you did not change bank 1 sensor 1 then. There is an o2 sensor for bank 1 on the front of engine closest to radiator angling towards the drivers side fender. Thats the one you needed to change out/test for functionality.
The other thing to do is get a bottle of water and while engine is running pour it around throttle mounting area where plastic manifold bolts to throttle body. Listen for water getting sucked in also check pcv lines and fittings at throttle body.
Ok so now I'm very confused. I was told there was only 2- O2 sensors. The one right behind the engine and the one downstream. So are you saying there's 3?
What i would recommend is check fuel trims at idle then at a steady 1500 rpm and then at 2500 rpm. If they get closer to zero on both then it would be a vacuum leak issue. If it gets worse it would be a fuel delivery issue (either a fuel injector problem or fuel pump or pressure regulator) but you will need to test each component.
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