Hi all--
First post here so greetings to everyone.
I'm driving a '99 GTP which has been throwing a P0171 recently, system too lean on bank 1. Figured it was a fluke so I just cleared the code out, and it comes back every time I start the car up, within 3-5 minutes. In addition to this, the engine bounces around at idle when warm.
I tried first cleaning and replacing the MAF sensor, and thought that fixed the problem because the bouncing at idle disappeared when the MAF was pulled, but the code (and bouncing at idle) came back immediately with the MAF inserted. So, I think it's a new MAF and splurge on the part - no dice.
I changed out the vacuum lines about a month ago so I haven't bothered to check them yet (will likely do so tomorrow or Tuesday), but I monitored the AFR and it never climbed above 14.7:1 at any time driving, but the SES light came on nevertheless - this makes me think the vacuum lines aren't the issue.
Before I throw any more money on parts that may or may not need to be replaced, any thoughts on this?
(I'm thinking it's the O2 sensor.)