plastic under intake manifold
 

Was looking things over and noticed some broken plastic pieces in the valley of the motor...so under the intake manifold. The plastic is kind of thick but very brittle. I was able to get some of the pieces out but more or less broke pretty quickly.

Getting ready to possibly pull the heads off anyways to replace the head gaskets, but was curious what that plastic is so I can replace it.

I'm pretty sure mine being a 99 I have a metal intake, so not sure what that plastic box thingy would be.

Anyone know? How concerned should I be about the plastic being all broken up?

Thanks,

The black plastic box is a PLENUM extension that tunes the intake for more torque.
The parts you see is the insulation cover that has come apart.
You should see an electrical connector in the front that runs a motor inside to change the air path length when signaled by the PCM, at about 2800 rpm +/-.
There is very little written about this feature.
Good luck.

Interesting. I tried to search but had no clue what it does or what it was called. I guess I'll have to check it out when I take things apart.
Thanks for the reply.

That plastic insulation layer isn't replaceable. It was glued onto the lower intake plenum. You could replace the lower intake Plenum. That's a lot of money for just a little insulation. If you were truly worried about intake Plenum heat soak, you could wrap it with some thermal blanket or other type of aftermarket insulation.
If you have the lower intake Plenum without the torque tuner, Dorman makes an aftermarket all aluminum lower intake Plenum. If I recall correctly it's around $260.

total necro post, but trying to put this back together tomorrow, on my 2001 --- custom

anyways, I got the dorman aluminum lower. do I need the plastic insulator thing also or no? I am hoping I do not

The plastic and insulated cover, is to keep engine heat from the block off bottom section of intake manifold.
If there is an electrical motor connector in the front, this is the IMRC for the 4.6L engines in a different form.... from what a V6 uses.
Heat reduces power. Example:::: Stock cool air intake system through the fender panel area drivers side.

yeah, it is a 2001 5.4L 2v but I am putting a 1999 PI aluminum upper and a Dorman aluminum lower on it.....

I don't have that fan thing on the front so I had to make a custom block off plate for it.