Nicols400

I have a 1993 lexus ls400 with a 1uzfe. The engine breaks up right when it hits 3000rpm when accelerating, falls flat on its face. Its not a misfire, it seems like the air fuel ratio is bad right when it hits 3000rpm. I can smell gas in the exhaust. Its worth noting the engine has power as it should through the full rpm range when the engine is cold. Once it starts breaking up at 3000rpm if I continue to give it gas it will struggle to rev up and really resist, but will slowly reach about 3500-4000rpm and jump back to good power and take off. Also has same issue if engine is not under load such as reeving it in natural. I am not sure what the issue is, possibly the fuel pressure regulator? Any suggestions on what I should look into would be appreciated. Note: Replaced ECU last year due to different issue so most likely not an ECU issue. And I also replaced spark plugs 3 months ago for general maintenance so also most likely not the issue. I run 91 gas.

dicer

You should start looking for fault codes. A suspect is the engine coolant temp sensor. Yes check fuel pressure too.

basilpluss

Honestly, I would run 1 can of seafoam per every 10 gallons of fuel. Had an issue once where the catalytic converters were actually clogged up. Seafoam helped after a couple days of driving. And if you are really crazy just dump two bottles of 99% rubbing alcohol into the tank.