I need some advice! I've got a 87 4runner 22re that i just installed a header and a 2.25" exhuast systems, cat & muffler on. It's been installed for about a mounth and a half now. I've noticed since the mods my gas mileage has dropped off significantly. I'm talking about 80 miles on a tank. Can anyone help me out with some suggestions or adjustments i may need to make or is the norm for these types of mods?

 

Is it a 5spd or auto. Are you driving any harder? I've noticed i burn more gas w/ the 300zx ever since i got my cat-back and intake. I tend to drive a "lil" harder.

 

It's a five speed and i do not think i'm driving any harder.

 

Did you get a power gain with the header as expected?

 

may be the o2 sensor?

 

Yes, when i added the header and exhaust i did get a boost in the power. I 'm able to climb smaller hills with much more ease! And there is a noticable throttle response. The one thing i forget to mention is i noticed that is smells like i'm running rich(gas smell in the exhaust)?

 

That seems like a pretty big drop. You should only have about a 13-14gal tank so losing around 6mpg is big. It could be some sort of problem with the O2 sensor or it could just be coincidental.
What did you have to do to the o2 on the install? Granted if there were any real issues with it, it would probably be throwing CEL codes.
I'd say, pull the EFI fuse to let the computer reset so it can get accustomed to any new readings that might result from the exhaust mods and check/adjust the TPS. The TPS is big cause of problems on the 22res and a pretty easy place to start.

 

When they installed the 02 sensor they cut the mounting bracket off the existing exhaust system(it was located under the truck in the front section of the exhaust pipe) and remounted it on the new system in the exact same location. I did scrape it off a little with my pocket knife before he reinstalled it. I do not get any CEL codes. I do get a code once in awhile at first start up and as soon as i shut the engine off and restart the check engine light goes out. But that has been an on going situation that i do not believe is related to my mileage drop off! I have an extra TPS i'll change it out and see what happens.

 

I have a 3rd gen and have had similar mileage issues. I've only had the truck for five months now and have noticed significant drop-off in gas mileage. I just did full maintenance on the truck and was hoping for improved gas mileage. With just one tank, it's still getting worse. My truck has not thrown a code but I think it's the O2 sensor. Here's a link with other 3rd gens with similar issues. One guy changed the 02 sensor b/c of a code and went from 13 mpg to over 18 and even 20 mpg since the change. Good luck.

https://www.yotatech.com/forums/f2/getting-13mpg-o2-sensor-65838/

 

check ur air in ur tires

 

Brand new tires. Just took off my 31.5's and put on a brand new set of michilns. I've got an extra set of rims so i took off my offroaders for a street tire. Still no difference.

 

make sure there are no exhaust leaks before O2 sensor