Fuel soaked plenum gaskets...

[19dabeast85]

I pulled the plenum to replace the "cold start high idle" valve underneath the TB because of an erratic cold idle i've been having.

I found both plenum gaskets to be soaked in fuel except on the very outside edges where some portions were just soft. There was a little oil mixed in from the pcv system, but definitely a strong smell of fuel on the wet gaskets.

Also, all of the inside edges of the gaskets on the rear runners (H23 IM) look burned and crispy like the fuel in the plenum has been slightly igniting at times...??

Is it possible for the fuel mixture to come back into the plenum? Doesn't seem like it should be. Thinking this may have been causing at least some of my idle issues.

I'll get pics up a little later tonight.

[19dabeast85]

Here's some pics, sorry for the huge one but wanted to show the discoloration of fuel. The whole center sections were saturated, some of the outer barriers were wet but all outside corners were dry:



What looks like burnt-crispy edges:



Have very small puddles in the runners that you can't really see here:

[19dabeast85]

Updated with pictures. I've got it all put back together with a new fast idle valve & new IAT sensor. Put new gaskets with RTV this time especially where the upper plenum vacuum ports die into the IAB plate.....very potential vacuum leak there.

Now to figure out why my gaskets were fuel-soaked??

[F22HB]

Don't think thats from fuel. How would fuel go the oposite way of the vaccum??? Thats what all my gaskets looked like when I took mine apart too. The oe gaskets tend to be kinda rubbery, which is what you want. Pretty sure your good.

[19dabeast85]

1. This is definitely not the first time I've removed honda plenums.......never seen them exactly like this.

2. These were dry as a bone around the edges in most places but extremely wet on the insides. You could argue the it's just the oil from the PCV system, but I'm running a catch can so only a tiny bit of oil gets through and that still does not explain why the gaskets smell very strongly like gasoline. I'm with you in that it makes no sense that fuel could ever flow against the vacuum, but then I swear these gaskets are drenched in fuel, what gives?

[cp[mike]]

im going to say that that wetness is oil from the PCV system, which would lead to the brown edged gaskets, and the fuel smell could be from blowby, giving the oil the smell? have you smelled under the valve cover/oil cap?

[19dabeast85]

im going to say that that wetness is oil from the PCV system, which would lead to the brown edged gaskets, and the fuel smell could be from blowby, giving the oil the smell? have you smelled under the valve cover/oil cap?

I haven't smelled under the VC within the last week, but I do do so randomly just because I like the smell of oil! Yeah, I got problems, lol. I'll take a sniff at it though and see if it resembles fuel.

I probably don't need to worry about it, it could just be that the plenum just begins to smell like fuel since so much goes through the injectors.