p1177 and p1179
 

Title says it all. I believe that these are for FMFR and AMFR. MAF is clean, plugs and wires are new. MAF seems to be about 3 years old. Fuel pump is also new. I did all of this work about a week ago, and I started getting these codes yesterday. No performance issues whatsoever. Getting about 13.5mpg on 91 octane (highest octane in CA) with only city driving. Does anybody know how to fix this?
Thanks

Edit: Long term fuel trim: -24.2%
Short term fuel trim hardly goes above +/-5%

Just replaced the fuel filter today with a Wix filter. No rust on the fittings surprisingly so it was a quick job. Did this because I don't really know when it was changed last and the FMFR minimum value code leads me to believe that the fuel pump had to work hard to pump through a clogged filter. Just a guess, but I'll see if the code comes back tomorrow.

P1177 came back, but now P1179. It's weird because everything seems to operate normally. Other threads usually mention other codes or performance issues, but I have none. Any help would be greatly appreciated.

just my 2 cents but start with the GEM's Land Rover Discovery work book to confirm what the norms are for your Oxygen Sensors compared to what they are reading. You could be needing some new 02 sensors.
From what I recall reading your long term trims seen low I think that is what the 1179 is indicating.
just 2 cents

Thanks for that. Will definitely check the O2 sensor readings. If I do need to replace front O2 sensors, any recommendations on brand?
Thanks

O2 sensors for a D1 w/ AEL (being a 99 yours has AEL)

Just tested all of the O2 sensors today on my scanner. The front two failed the transition time test so I guess I need new O2 sensors in the front. Thanks for the recommendation, just ordered them.

Changed out the front sensors today. I still get pending codes, but no CEL. Does the ECU need to get "used" to the new sensors for these to go away? Or do I have another issue?
Thanks

I think it does have a "learning curve" from what I have seen, but that may not be a proven fact.

My MAF proved to be the cause only after I changed 3 of the 4 o2 sensors. There was a slight change in values (higher) on my 2 downstream readouts when I changed MAF's and the 1179 stopped popping up.

I would drive it for a while to see and maybe swap with another MAF if available to see if it makes a difference.

Just drove it about 30 miles. No CEL, no P1179, but still a pending P1177. MAF sensor is about 3 years old so I'm a little hesitant on replacing it. But if the CEL comes back, then that will most likely be my next move.

If the code stays as pending and CEL doesn't come on, then I'll just leave it alone. But I'm pretty sure that the CEL will come on any time now.