Dukenukemx

Got this car as a gift for my Uncle and been doing a lot to this car before giving it to him, and I'm getting P0171 constantly reoccurring. I've changed the rear O2 sensor before the cat with a Denso. I've cleaned the MAF sensor and even swapped it with my dads MAF since he drives a 02 RX300. I took out torque on my Android phone and it showed 20% on my short term fuel trim on bank 1, but bank 2 is nearly 0%. I was thinking maybe vacuum leak but wouldn't that effect bank 2 as well?

I did remove the top of the motor to change the valve cover gaskets and replaced the plenum and throttle body gaskets for good measure. I was told when we got the car that it may have a bad O2 sensor, hence why I changed the rear and it did give a code for that O2. But I can't figure out why bank 1 runs lean.

Dukenukemx

Checked the fuel trim again and Bank 2 short term is +- 3%, which looks good but long term is about 6-7% which I don't know if that's good or bad but it isn't anywhere near as bad as Bank1. I figure I must have screwed something up when I put the new intake plenum gasket on cause bank 1 has a long term fuel trim of 50%, which is nuts. I figure if there's a vacuum leak in a hose or in the throttle body then it would effect both equally but that's not the case. I'll dig out the Plenum tomorrow and report what I find.

salimshah

Just reminder Bank 1 is near the firewall and bank2 is near the radiator.

Salim

Dukenukemx

Just took apart the plenum and put RTV Red Gasket maker on both sides of the intake gasket and no change. Took apart the throttle body and checked the gaskets with nothing looking incorrect. Double checked the vacuum lines with nothing looking wrong. The good news is that the Bank 2 reads 0 for both short and long trim, but Bank 1 still has 50% long term and 20% short term.

I'm stumped. I did replace the pre-cat O2 sensor a week ago for Bank 1, so I'd imagine that's working. Maybe the issue is a clogged fuel injector? But I also get misfire on 1 3 and 5, which are the entire back side of the engine. Can't be all the injectors, unless they're all controlled together which means one bad injector could effect the entire bank?

Dukenukemx

Ok, I removed the fuse for the EFI and soaked the MAF sensor in cleaner and then started the car and everything works fine. Bank 1 short term fuel trim hovers around 0% while the long term trim is about 2.5%. Thems good values. Either I fixed the vacuum leak and the computer needed to be reset, or it was something stupid like a MAF sensor needing cleaning. I'll test it later some more to make sure.

maxSteel

Hope your problem is resolved. If not there are multiple threads on this.
One of them had this link, it taught me a lot.

Dukenukemx

Thanks, yea the problem is fixed though I don't know what I did to fix it. That's the problem when you pull a shotgun approach to fixing things, you just don't know which one did the trick. I pulled out the plenum and put red RTV on the gasket plus I cleaned both the intake and plum with a wire wheel on a Dremel. I took apart the throttle body and put smaller O-rings for the coolant lines cause I put large ones before and thought it maybe interfering with the gasket seal. I soaked the MAF sensor in MAF sensor cleaner and then put it all together and nothing changed until I unplugged the EFI fuse and waited and then plugged it in and started the car to find normal Bank 1 and Bank 2 fuel trims.