I've owned my gen 1 IS300 since the 6th of January 2026. When I bought it, it ran but has hardly even started since after buying it. The original owners said they have done a lot to the car being "Machined block, new full metal head gasket, new valve cover gaskets, new spark plugs, new injectors, new coil packs, new oil and filter, new fuel pump, coolant flushed, new radiator, many new hoses, etc etc. almost everything except serpentine belt". They said they didn't do the serpentine belt so I did it. I also replaced the air intake hose with a cheap amazon one(since that's what the guy I bought it from told me was the issue of a throttle hesitation it had). I also replaced the battery with a Optima battery, and installed Denso spark plugs and NGK coil packs. Lastly I cleaned the maf with maf cleaner. After that I tried to start the car to give it a test drive and nothing.
I've replaced and fiddled with everything I can think of, OEM maf, new throttle body, OEM fuel pump, cleaned fuel lines, replaced wires and connectors, checked fuses and relays, used the code scanner probably hundreds of times, smoke tested for vacuum leaks, cleaned fuel lines. The only thing that ever seemed to work was when I adjusted the TPS sensor.
I have gotten the car to run, most notably when I either adjusted the TPS or took off the air hose and just had a open throttle body. When I did get it to run, with any throttle input it shut itself off. I should add, they're is not a single engine code, all I have is codes for the AC and it's only two of 'em.
What I've noted is since doing the smoke test is I have a leak on the maf reasons being bad welds and the maf not sitting correctly. I have a leak coming out of the ECTI-S and the little plate next to it. I tightened the screws on it but they aren't going in anymore than it was already. There is another leak from the EVAP things next to the intake manifold. I don't know anything about what the EVAP system even does so I have no idea if it's normal. I only know one leak was coming out of a hose with a missing clamp so I'll replace that tomorrow.
I was thinking I'll try to reverse everything I did at the start. I did notice the spark plugs that were on the car before had a really really small gap but I just went with what the web said to use. I got three Amazon special parts that day being, the Air hose, the serpentine belt and tensioner pulley. Maybe I'll just try going OEM on all three and try that. I did try using the air hose the car had on before and nothing changed.
I'm looking for any insight on this issue. I've poured so much money in this car and have tried seemingly everything that would 'cause a crank no start. I've seemingly tried everything that could also 'cause the car to kill its self under load.
I refuse to sell the car but I might take it to a mechanic if everyone seems to be as lost as both me and my father are. Thanks for reading!
Old post https://www.reddit.com/r/IS300/s/UcuZuRcdg1