Help with Fuel Injectors

[TonyB44]

Hello all, my starter went kapuut on my 00 LS400 and I've decided since I need to pull the injectors I will replace them while I'm there. I'm however a bit lost on buying them. Rock auto is my go to and they have quite limited options, and it seems as though cylinders 1-4 use a slightly different injector than cylinders 5-8. I don't really want to spare any expense, but I'm confused mostly on whether those one on rock auto come as a set? The SMP injectors on rock auto are ~$160 for either 1-4 or 5-8, but say nothing on how many it comes with. Whereas velocity Titan has injectors that very obviously state come in a set of 8 and are ~$100. Just curious what other LS400 owners or mechanics who've done this went with as far as injectors (not interested in remanned) and really confused on the quantity of those rock auto ones. Thanks

[McBrian]

Never understood that design, but do you really need to replace the injectors?

I truly get the "while I'm in there" thing, but are you having an issue with fueling and running?

Can it be down long enough to have them sent out to be patterned and cleaned? Much cheaper and you know you have good OEM parts.

[TonyB44]

Absolutely no problems with fueling, I just initially assumed it wouldn't be over $1000 to replace the injectors, I had in my mind they were closer to spark plug pricing. The car has been done for a couple months anyways unfortunately as I hear up to do the starter so sending the injectors to be cleaned mat be the move. Appreciate the advice

[Bobby T]

I have a question,im thinking anout cleaning with a cleaner in arosole theu the feul rail ,any one have a step by step,and another is I know newer cars get better milage is there an injector set that atomizes the fuel for better milage or something? 99 LS 400

Edited June 29 by Bobby T

[RX400h06]

5 hours ago, Bobby T said:

I have a question,im thinking anout cleaning with a cleaner in arosole theu the feul rail ,any one have a step by step,and another is I know newer cars get better milage is there an injector set that atomizes the fuel for better milage or something? 99 LS 400

Great questions, Robert — and very on-brand for someone who knows their way around a Lexus V8 like you do. Let’s break this down into two parts:

🧼 Cleaning the Fuel Rail with Aerosol Cleaner

Spraying cleaner directly through the fuel rail isn’t a common DIY method, mostly because it requires pressurizing the system and bypassing the fuel pump — something typically done with a professional-grade fuel injection cleaning kit (like a MotorVac or OTC tool). However, here are safer and more accessible alternatives:

• Throttle Body Cleaning: This is a great place to start. It’s known to improve idle and throttle response. There’s a step-by-step guide with photos for cleaning the throttle body on the LS400 without removing it entirely.
• Injector Cleaner via Fuel Tank: Using a high-quality cleaner like BG 44K or Techron in the gas tank is a safer way to clean injectors gradually. Just make sure your fuel filter is fresh — otherwise, loosened debris can clog it.
• Professional Injector Cleaning: If you're set on cleaning through the rail, a shop with a pressurized system can do it properly without risking damage.

[McBrian]

Agreed on the above.

Throttle body cleaning and a fresh air cleaner do WONDERS for fuel mileage.

Two tanks of premium (ideally 93 E0) with a can of BG44k each and drive the crap out of it is the best FI cleaner out there. Most of the benefit comes from long drives at highway speeds.

The fuel rail cleaners and aerosols into the fuel rail, etc are pretty much worthless and especially that one at the dealership...

Fuel injectors atomizing hasn't really changed since they were designed. Cams/timing, engine size, friction management, injection type (port vs direct,) and NA vs forced are the ways fuel economy has gotten better. You got a "old" V8 in a big car. It's only gonna get so good.