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My 2002 Rav4 is running lean. The Long term Fuel Trim on Bank 1 at idle hovers around 14 to 16% and on Bank 2 around 3 to 7%. While accelerating both LTFT are increasing and while driving at highway speeds around 60-70m/h the LTFT on Bank 1 stays at 19.5% and on Bank 2 stays at 13%.

I've kind of excluded the possibility of vacuum leak at which the LTFT would actually be decreasing while accelerating instead of rising. Possible causes could be either a dirty MAF sensor, weak fuel pump or maybe some other fuel delivery problems? Few other things are happening with the car as well; 1] car stalls for just a second at stop light or intersection from time to time very randomly tho. 2] also this only happened few times that the car's idle got very low at stop at around 300-400 rpm. Car started shaking, with rough idle but as soon as gave some gas it drove ok.
Little history, year ego, I got a P0420 code and had my Cat replaced. Last month I got the same code again plus P0430 and had the same CAT replaced under warranty. Now I am thinking that maybe the fact that the car has been running lean all this time caused the CAT to go bad twice on me. Since there are no codes, no mechanic ever bothered to look into the reason for the CAT going bad. Where should I start to look? Whats the most possible cause for the engine to run lean? How do I change the fuel filter or replace the fuel pump myself? Are there any other tests I could run to zero down on the problem? I am looking forward to any suggestions... Thanks

I've kind of excluded the possibility of vacuum leak at which the LTFT would actually be decreasing while accelerating instead of rising. Possible causes could be either a dirty MAF sensor, weak fuel pump or maybe some other fuel delivery problems? Few other things are happening with the car as well; 1] car stalls for just a second at stop light or intersection from time to time very randomly tho. 2] also this only happened few times that the car's idle got very low at stop at around 300-400 rpm. Car started shaking, with rough idle but as soon as gave some gas it drove ok.
Little history, year ego, I got a P0420 code and had my Cat replaced. Last month I got the same code again plus P0430 and had the same CAT replaced under warranty. Now I am thinking that maybe the fact that the car has been running lean all this time caused the CAT to go bad twice on me. Since there are no codes, no mechanic ever bothered to look into the reason for the CAT going bad. Where should I start to look? Whats the most possible cause for the engine to run lean? How do I change the fuel filter or replace the fuel pump myself? Are there any other tests I could run to zero down on the problem? I am looking forward to any suggestions... Thanks