Previously, I'd run across some information on cleaning the intake manifold on the car by using vacuum hoses to suck in cleaner or ATF fluid while the engine is running clean the manifold and thereby increase performance. After that, I ran across this picture of the inside of the upper half of the VG Intake manifold a guy was selling on Ebay:



Shortly after that, I ran across a post on Sentra.net by a certified mechanic that warned against doing this. He claimed oil vapor from the PVC system combined with intake dirt forms a thick "not very combustible" sludge that can come off in large pieces. He claimed these pieces can lodge on valves, pistons, and even go all the way through to the Catylitic converter and damage it.

Any comments on this? Is this paranoid bunk?

NOTE: I've already spent hours searching all formums on this site for info on this. The posts may be there, but the Search feature is not finding them. The search feature is also not finding other posts I KNOW is here.

 

It's not a bad idea. I'd take it off and clean it by hand if I were you. I didn't clean and port this one (Thanks Mike!) but you can see the difference between that dirty one and this clean one



I do kinda expect to see a LITTLE bit of a gain when I put it on because I'm sure mine is incredibly dirty

 

Nice Job, KLoWnPR109. I plan to do just that eventually; I'm going to need to replace injector harnesses, injector O rings, and possible an injector sometime in the next year plus I plan to do some throttle body and maniflod porting work when I DO get around to it. But I've got DIY projects for may car stacked quite high right now, and pulling the intake maniflod is a ways down the road.

My question was directed to doing in on the car WITOUT removing the manifold.

 

Sucking ATF or water through the engine used to be a old machanic trick to try to clean the ports, free up gummy valves and dislodge carbon deposits. It worked sometimes and sometimes not. Seafoam and Winns has a product that is used like this. What you would do is rev the engine up and suck a steddy amount of the fluid into the engine. Lots of smoke out the exaust. Keep rpms up untill smoke goes away.
I don't know if I would try it on the newer vehicals. It may have na effect on the O2 sensor and might damage the Cat-con. But I still see stuff for sale inthe stores, so it might be ok.