Injector Advice Needed - Runs Lean (Not Stock!)

gamefreakgc · 2017-10-04T16:13:51+00:00

Anyone with tuning/custom build experience, your advice would be appreciated! I have a Supercharged 5VZ-FE engine with larger intake, swapped the MAF for the less restrictive 99-02 MAF, Deckplate mod, headers, and other things to help air flow in and out much quicker. Let's just say I've succeeded and now I've got a problem. My engine runs lean. Not under boost, I have a methanol injection system that takes care of that. I'm talking about driving around town or inching along in traffic. My long-term fuel trims go between 16.5 - 19.5. At idle, it's pegged at 19.5, which is the maximum value. Which means, if I understand this right, my injectors flow is increased by 16.5%-19.5%. A value of 20% or more will throw a check engine light. The short-term trims stay near 0% for the most part, which is good. Last part, when I had the headers installed it ran a little funny (turns out it was running lean, but I didn't know that yet) so I went ahead and pulled the EFI fuse to reset the fuel trims to stock. Bad idea! My AFR at idle, 10 MPH, 30 MPH, etc. was pegged at 17+ AFR. A few times it went unreadable, over 18 AFR. Finally after about 10 minutes of driving the computer kicked in and went back to 14.7 but scared the heck out of me for a while. So, that leads me to my question, do I need larger injectors? Our stock injectors flow at ~240cc. If my math is any good, just for stock driving around town I would need injectors between 240 * 1.16 (278.4 cc) and 240 * 1.19 (285.6 cc). I'd probably push that a little higher, since I need more fuel anyway with the S/C system. Does this sound right? I'd appreciate thoughts. P.S. I am buying a piggyback controller very soon. This is the stock injector we have, measured by WitchHunter Performance (an injector servicing company):

Thread starter gamefreakgc
Start date Oct 4, 2017

gamefreakgc

Elite Member

Oct 5, 2017

19963.4lsr5 said:
Yea, I wondered what year he's got because of the comment about going to the newer MAP sensor. Blowing a .88-.93 is good WOT if he has got the narrow band older 1v sensor. If he's able to already see the AF ratio than yep........

Sent from my iPhone using Tapatalk

Oh, yeah I installed a wideband in a while back.

Changing the MAF from a 96-98 to a 99-02 though does not require one though, the computer adjusts fine since it's still a 4Runner part. Just allows a lot more air in so it adjusts the fuel trims.

EDIT: Fuel filter was replaced two years ago, and the gas I get here in CA is good quality, we don't have issues with clogged filters.

Last edited: Oct 5, 2017