I wanted to clean this to address some rough idling on my 98 CL 2.3 but couldn't find where to do it, some clues in this thread https://acurazine.com/forums/1g-cl-problems-fixes-71/99-2-3-egr-port-locations-495350/ on splitting the intake manifold.

Here's what mine was like.

I split the intake manifold upper portion, leaving the complete throttle body on the upper manifold. Not too hard, just one hard to reach vacuum hose at the back on the left. No gaskets needed this way, be careful with the metal gasket for the upper manifold.

Mine was not completely 100% clogged but still pretty clogged and filthy after 135K.





Here's my EGR passage after cleaning below, from the rectangular hole under the removed EGR valve it runs diagonally up to the corner of the lower intake manifold, you can see the corner of the metal gasket in the upper right hand corner of the photo. You can get a small screwdriver in to clean our carbon and crud but mostly have to reply on spray on the diagonal passage, used two cans, both Carb/Choke cleaner and brake parts cleaner, both pretty effective. Try to keep all the carbon particles and cleaner fluid from running down the intakes into the cylinders, you can mop it out.



Here's my intake manifold lower and upper after cleaning ready to put back together, no real tricks there.





Unfortunately, didn't cure my stumble and rough idle.

Good luck and happy cleaning!

 

Nice work, thanks for the writeup

 

Nice and well pictured examples. I do have a question: Do you have to replace the EGR valve since everything else was cleaned? My thought is that carbon will clog the EGR valve too (right).