Tacoma

I have a 2005 crew cab 6speed Tacoma with a 2015 engine my truck is terribly weak I work on vehicles for a living put this motor in and everything but this has me stumped the truck is weak and it gets 7mpg yep 7mpg it does have roughly 5 inch lift and 20x14’s with 33’s which obviously will hurt mpg but people are getting 18-20 in theirs I think 7 is to low and that still don’t explain why you about need 4 low to take off someone please help I’ve done all I can think of

 

You have a check engine light on?
If you need 4Lo to take off, something is B.A.D - bad wrong.

There has to be some signs of something wrong.
Have you done a compression test?
Looked at scan tool data?

 

I don’t need 4lo to take off just using that as an explanation you about have to on a hill but it’s bad compression is good I’ve hooked it to computer and all it says is a code for knock sensor which I ain’t worried about and a code for running lean I’ve checked everything can’t find anything causing it to run lean the motor in the truck barley has 80k on it that’s what has me stumped

 

Follow that lean code until you find it. That's for sure an issue.

 

Do you have any exhaust leaks. The 2015 heads have port for air injection.
How did you get by that? Headers or 2015 manifolds?

Exhaust leaks before the A/F sensor will throw a lean code and pour fuel to it.

 

Oversize tires will definitely hurt performance and make it more difficult to take off from a stop without regearing.

A knock sensor code will force the engine to base timing so that will hurt performance, you also need to track down the lean code too.

Is your air intake stock?

Did you use the engine harness original to the truck when the engine was swapped?

Was the truck fine prior to the swap?

What code numbers do you have? Just saying a lean code and knock sensor code isn't very descriptive.

 

Replying to all:I’ve done what most people would do I’ve done plugs of course that was first step cleaned maf checked all vacuum hoses made sure they was where they needed I do have slight exhaust leak but it’s around the muffler I have original 2015 manifolds I cut out a plate and welded it over the air injection port on both sides and capped it off it is possible they are leaking and I understand my tire and lift situation hurts mpg and power but 7mpg is something wrong I bought the truck blown up put a junkyard motor in it hit or miss deal it ran good but not for long till it blew up so I bought the on that was in it with proof of running and mileage and it has ran great for a long time but it has done this every since it has factory 2005 intake so I could get rid of all the stuff connected to the 2015 intake everything on the truck is factory except for cosmetics

 

What are your LT fuel trims?
That lean code is not helping fuel mileage at all.

 

I used original harness to and it has code for knock sensor and running lean bank 1 I think is what it says I am using one of snap ones best to not to familiar with the scan tool yet but trying to get as much as I can to share I know these trucks really well but this has me puzzled and I can’t find anyone with the same issue on any forums

 

I will have to hook it back up to figure out fuel trims and all that for youns but I’ve been told anything from plugs to clogged cats to needing ecu flashed

 

Since it sounds like you have a lean code on one bank only I would want to look at fuel trims on both banks and see if there is a big difference.

 

Okay and if fuel trims are off what’s a solution for that I’ve already swapped fuel rails 3 times from the blown motor that was in it when I bought it the junkyard one and the one in it now and didn’t fix anything

 

Have you looked at fuel pressure yet?

 

Catalytic converter plugged up?

 

I have not I was also told fuel pump could be going out supplying to much or the pressure but not the amount causing stuff to go out of wack

 

Lean codes don’t always mean fuel problems.
Lean means air/fuel is not within range.

But as @b_r_o said, you can take a look at the fuel pressure.
You need to remember these truck operate at 2 speeds. So you need to drive it to get a good reading.

 

Really need more data, can't just say fuel trims are off and ask what part to throw at it. You need to see what they are at different loads and how they vary from bank to bank.

 

@420taco did a 2012+ swap in his pre-12’ truck.
Maybe he can tell you the essentials of the swap.

 

I did a bit of research on the Knock Sensor code.
When it is set, the truck enters fail-safe mode.
The timing is set to MAXIMUM retardation.

This alone will make a dog out of the engine.

 

....and rodents just love to eat through the knock sensor wire and short it out on the Taco....yum, yum