Since before the 5.4 swap, I've have a lean on bank 1 and 2, classic 171, 174. Now I've got a malfunctioning 02 heater on the 4th sensor. Are these killin my milege? I only see about 250 miles per tank, 26 gallons. I checked up top for leaks, sprayed my brake cleaner, nothing, never spiked RPM. I know I have a small hole in the passenger side downpipe I have to weld, and also a spilt in my H pipe thing. Either those holes are hurting me or the sensors are bad.


What we thinking?

 

the sensors are most likely working with the lean codes. did you check the pcv elbow? did you get a tune for the engine swap? the heater circuit problem may be the sensor but check the connections and the wiring.

 

yea, its tuned for a 5.4. diabosport

 

Your not kidding, somethings up! I have a 23 gallon tank and if the truck doesn't get 360 miles out a tank, I know there's a problem.

Last time I got real bad mileage like that was when I installed Borg Warner O2's in B1S1 & B2S1.

I thru my old Bosch parts back in and got my mileage back. I had No codes tho and it seemed to be running fine.

Yea, you have a leak somewhere or somethings not connected right .

 

also have to calculate I have 3.55's, a much bigger and heavier tire(285/75), and just general weight of stuff in truck, tools and such. Its getting warmer so I definately want to get my exhaust sqaured away.

How much am I looking for for 02's

 

bosch are 40-42 bucks on rockauto.

 

my leaks are all after the first sensors, so those wouldnt pick that up I wouldnt think. Maybe I'll have to sqaunder and buy them. . .

 

if the leak is after the first oxygen sensor then there is no problem with them. You probably have a very small vacuum leak. I would just start spraying carb cleaner around everything and see if the idle changes at all. That mileage probably isn't too far off with the size of the vehicle, the gears, and the tires.

 

I used about a whole can trying to trace a possible upper leak, came out with nothing

 

Your tires are a big factor. I have the same tire size on my truck and those are about 4-5 inches bigger then the stock ones. Your speedo is probably about 10-15 percent slow so that means your really getting closer to 300 a tank.

 

IT reads somewhat slower, didnt think it would be that much of a cut back. I think its 3-4 MPH behind at 45