3.4 running rough with codes

[Adumb]

My dads 99 4runner with the 3.4 has codes p141 and p171 coming up. It will start up and run good and even drive good sometimes. Then it will start sputtering and misfiring. We are kind of thinking its a plugged cat but it seems wierd the way the problem is either off or on. It almost seems like it could be something electrical. Does anyone have any input or ideas on this?

 

[LittleCaesar]

Are the oxygen sensors original? Check the wiring to them as well.

 

[Adumb]

Are the oxygen sensors original? Check the wiring to them as well.

not sure if they are original but will check the wiring, thanks!

 

[TheDurk]

P0171 most often resolved by cleaning the MAF sensor and that certainly can be the source of your issue. Search on p0171 for more info.

P0141 is your rear oxygen sensor heater and almost always requires changing the rear sensor, but could be the wiring. It is not likely to be the source of the running problem, as the only function of the rear sensor is to check on CAT function--no effect on performance.

 

[rmlamp]

Clean out the MAF with a good MAF cleaner and reinstall. Clean the throttle body too. Whens the last time it's had a tune up? Rear O2 need to be replaced more than likely.