cat coverter and sensors replaced and still bad mpg

I just had my both cat. converters and both sensors replace and it seems that I am still getting bad mpg. I was under the impression that the mpg would go back up to close to the 20 mpg. It seems that the mpg is staying around the 11 mpg. Should the mpg after replacements go back to normal? Could there be anything else that is dropping the mpg by half?

 

You replaced those only because poor mpg? No CEL?

I would start with basic maintenance like spark plugs and cleaning the maf.

 

Sorry, new to forum what is CEL? And I am not a a big wrencher. I am not familiar with the lingo. I had two diagnostics and both came back with cat errors. They replace o2 sensors ran dianogstics, error code came back again replaced cats. Just finished the cats.yesterday. Is the maf. the manifold?

 

A CEL is a check engine light. I assume you had one of these on your dash before you replaced the converters?

MAF is a mass air flow sensor that is located on the air intake before the throttle body.

 

Have you also checked your tire pressure lately? It might be way to low. That will suck out a huge amount of mpg.

When is the last time that you changed your spark plugs?

How many miles are on the truck?

 

I bought the truck used, so not sure. If I were to guess they have not been changed. That is one things that I am going to do in the next couple of weeks. I am not getting any loss of power or sputtering when driving. There is about 160k so the plugs are on the list. That I can do with help not in a shop. I am going to check the tire pressure this evening.

 

The CEL( thanks for the lingo) is off for the time being but the mpg drop was sudden. One day was 19 mpg the next I was watching the needle drop running 2100 rpms. Thought it was the extremely cold weather but it never recovered. I thank you guy first the advice I will start in on the list and let you know what happens

 

first gen double cabs in 4cyl could get 20 mpg cruising on the highway but not as an average mpg very easily.

I Assume yours is a V6 pre-runner?

if you can squeeze 16-18 mpg be happy.

But yes all the stuff that should have been done to your truck at 120k or so miles is if a 5VZ 3.4 Liter V6:

Timing belt
Water pump
Check valve covers for leaks
Check exhaust manifolds for leaks
Replace O2 sensors front and rear
I got 200k from my stock cats so not sure why yours fried out
Clean throttle body, if possible have it taken off and fully cleaned both sides of butterfly
check and replace all vacuum hoses
Replace spark plugs with OEM dealer plugs for your vehicle only (no auto zone crap)
Replace plug wires and check for compression since you have a shop that can do this have them make sure all cylinders are firing fine and have good compression
Clean Mass air flow sensor on the intake tube with approved MAF cleaner only
Replace air filter with stock OEM paper filter from dealer or napa gold for best filtration
Tires properly inflated to spec pressure
Replace rear differential fluid and check for metal shavings
Replace transmission fluid check for shavings
Inspect front and rear brake pads, rotors, lines ect for sticking or leaks.

Sounds like a lot but preventative maintenance is cheaper than costly repairs and terrible mpgs.

 

Last sentence. Yup.

Correct me if I am wrong, but isn't the fuel filter replaceable on those year models? It should be replaced as well, regardless if it is easy or hard. 120k on the ticker, means that filter is saturated with contaminants.

 

Fuel filter is super easy to replace on first gens. Did mine at 120k and saw a small increase in mileage.

 

^^^^^There you go. Thank you sir.