Car is a 98 ES300

After a bit of troubleshooting Ive traced my lean combustion issue down to a leaky intake plenum.
You can hear it, and surely enough the classic carb cleaner trick revs up the engine some.

I bought a new gasket and installed it, though the old one didnt look at all damaged, maybe a bit flat if anything. That didnt fix it (you can still hear the poor thing sucking air in). I took all the proper precautions of torquing the bolts from the inside to out, and gave each 32lb ft.

I also cleaned the mating surfaces and inspected them closely, couldnt find anything by the naked eye. Could I be missing something? I dont think I skewed the installation but what might cause this to persist?

 

Maybe the bracket at the back is preventing the plenum from dropping down properly onto the intake?
http://www.japan-parts.eu/lexus/us/1...&pa=1712520010

 

That what my thought was initially, so when I installed it I torqued down the 4 main bolts first for a good seal before securing the rear bracket.

The leak is moderate, car puts down decent power up until it enters closed loop fuel control, then it barely wants to stay alive. I cant lie, the thought of putting some high temp gasket there has crossed my mind, but the thought of gooped up valves has stopped me thus far.

 

Remove the acoustic valve that's on the end of the plenum. At night (dark as possible) shine a light into the plenum runners see if you can see it leaking out anywhere. Tie a string to your light so you don't drop it into the engine!

Even better if you have a bendy style light.

 

Hello,

What gasket did you get?

One other option to add is to make sure that both mating surfaces are flat and square. You can use a flat rod that you trust to check for a gap, but it can get complicated without taking the intake completely off the car.

For a different way, you will need some very thin paint, almost like water, and something that you very much trust to be flat, the longer the better - apply the paint to the gasket surface and drag a reference surface across, then see where the paint wore off, which will tell whether your intake's mating surface is flat. Below is a similar process done to the vice, just to give an idea.


Hope this helps and best of luck!