Alright, I'll be honest. It's driveable, but I have the brain of a 13 year old and floor my car almost everywhere. Apart from that it's well maintained by me, and 2 owners previous, up to 220,000 miles, it was dealership maintained. But the owner in between, I'll assume he got it from a scrapyard. Front end held together by zipties and the title says he got it for 500 bucks. Sketchy work all over the thing. When I got it from him, it had most of its power, and could spin the tires from a stop in the dry. Then, the car sat for around 4 or 5 months, and was started once a week but never driven. Once I started driving it again, I noticed a fuel leak. Leaking injector (great) so I get a supposed "OEM" Denso fuel injector set and replace all 8. First fire up, running absolutely horrible and knocking. Probably detonation, but a very distinct knocking sound nonetheless. Sound went away after 30 seconds of idling, but in that time about 6 codes came up. For a summary, MAF code, System lean Bank 1, and Knock Sensor bank one. Since then it has cleared up, and I decided I wanted a little more out of it and chopped the exhaust off behind the resonator and put a turndown on it (with intentions of putting a full exhaust on it soon to come) but I am noticing very high lack of performance. When cold, the car will perform almost as well as it used to, but as it warms up, throttle response and power start lacking, and backfires, (off throttle and on throttle) start occurring. When you let off and go to give it throttle it'll pop fairly loud, and on throttle (light or hard, doesn't matter) there is an intermittent miss followed by a small backfire, which you can feel the car buck almost like it's brake checking you. I timed the 0-60 and it was high 9 seconds, I definitely recall it being faster before. I'm going to start listing off things I was told to replace, not sure if some will help but I'm just repeating what I've heard.
1. Knock Sensors, which may be pulling power and adding fuel to help "protect" the engine
2. Fuel injectors, the supposed "OEM" Denso injectors I put in there are rebranded cheap Chinese injectors, which I was informed of by someone on another forum
3. O2 Sensors, they may have never been replaced and could be giving a bad reading, leading to the engine running rich
4. Spark plugs, again probably changed a long time ago or never (doubt it) and could be giving me inconsistent spark
5. Ignition coils, one could be going bad and cause misfire and loss of power
6. MAF Sensor, never replaced and had a code, could be the root of running rich and loss of power
7. Put an exhaust back on it, apparently there is not enough back pressure with the exhaust cut at the muffler and that could be affecting how the engine runs

If you guys have any suggestions please let me know, I really want to get this thing running better so I can be more motivated to take care of it.

 

I suggest you find a lower mileage LS400 that is running properly and use the one you have now for parts. The knock sensors alone are a huge job. This car has had a rough life from everything you are explaining. You could dump 3-4K into it and the possibility it still won't be right. The stuff you are explaining sounds bad.

 

so in interpreting your timeline, i conclude that after the injectors swap was where the car started running poorly. was the engine running well despite the leaking injector?

what did you do to clear the codes you received?

 

probably the injectors, try putting in used OEM Lexus ones from another car and see if the problems go away. Should be able to find plenty of them in savage yards.

 

The engine was running great before and during the leak, no odd sounds, codes went away on their own except for o2 sensor, compression is within spec. I found out it is running rich, that's all the info I have for now. I plan to do injectors from a low mileage parts car I found, and while the fuel rails are off do the starter and knock sensors so I won't have to go under the intake manifold again.

 

Would cam seals also be in the scope of this project? They're typically done with a timing belt job but require a lot of other work as well. Your engine has VVTI and is more vulnerable to failure of these seals. If yours leak down the road, you'll have to remove the timing belt, valve covers and cams to replace the 2 seals. I don't know how much work you will have already saved if you're only pulling off the intake manifold vs. doing a timing belt job.

Food for thought & something to consider. Best of luck solving the issues with the car.

 

Timing belt is definitely on the list, but still not due for another 20,000 miles. I believe the problem lies in something fuel related, injectors as the main possibility as Loisracer2 said. Knock sensors, o2 sensor, injectors and fuel pump and spark plugs and ignition coils are on the list for possibly solving the issue, after that I'd start looking at tuning options to get back to around 12.7:1, which is where these engines like to run.

 

Use Toyota knock sensors. Knock-offs are trouble.

 

Usually it's the water pump or a pulley or bearing that goes first. But yeah there is still some expected life in the belt, presuming it's not super old and age'd out.

Lot of troubleshooting to do!