2nd gen taco fuel mileage questions

Hey all. Got a question about things I might be able to do on my 2g 4.0 Tacoma to get better mileage. Only getting about 284 km to a full tank. Truck is on 315/70r17’s 6 ply recently cleaned throttle body installed new k&n panel filter and changed all spark plugs. Truck gets code P0430 ( A/F ) sensors ( I’m assuming that’s the problem but unsure) planning a trip to California from Saskatchewan ( 6000 kms round trip )

 

That code definitely could be part of the issue. Points to O2 sensor, catalytic converter etc. A bum o2 sensor will definitely drop your mileage.

 

The P0430 is for a Bank 2 catyletic converter that is no longer functioning properly, if you have no exhaust leaks upstream or near the AFR & O2 sensors 95% of the time it's a bad converter.

That can affect fuel economy a bit as the PCM may try to richen the air/fuel ratio in an attempt to "light off" the converter but it shouldn't be a significant impact.

Not sure how your driving it or if it's lifted or not as those and having oversized LT tires makes a significant difference if fuel mileage on these trucks.

9 MPG seems low though but may be on par if your lifted with oversized tires and trying to run it 75 mph + down the road.

 

Granted I have a four banger, but when my catalytic converter went bad I lost about 5mpg....when I replaced it it was immediately noticable and my engine didn't hiss at high rpm as the bypass springs didn't have to compress and let air by.

 

How are you calculating/measuring your distance travelled? Your odometer might be off with the taller tires. My .02

 

Sounds like yours was plugged/restricted, a converter efficiency code doesn't mean the converter is plugged/restricted (although it could be as well) and a plugged/restricted converter won't nesseaarily set catalyst efficiency codes.

 

Fair enough, the reason I bring it up is the only code I hade was the P0420 and didn't have any other symptoms except bad gas mileage until reviving past 4000 rpm (pretty rare for me)

Hopefully the OP doesn't have to replace his Converters as the are expensive.

 

I think it may be cats… the truck is lifted with the 35’s when I had pulled the plugs to replace them they were all wet with fuel.. on highway I’m going 110 kmh so probably about 62 mph and I don’t drive it much faster than that. Truck also just hit 351,000 kms. Thought about replacing cats but they’re close to $800 a side so thinking of getting long tube headers and getting an engine tuner to permanently delete the P0430/p0420 codes as it is WAY cheaper to do it that way and will also give me some performance improvements.