What causes this? What I don't understand is how this carbon (which is just burnt fuel, correct?) gets all in the intake. I mean, only air gets in there right? Or does the EGR let a bunch of fuel in there and that's what causes this carbon build up? Man, I took apart my intake today and there is gobs of carbon buildup in the upper, lower and runners.

I just don't think this is normal. There must be something causing this. Also, I can really smell fuel in there, even though the car has been sitting for awhile. I wonder if my injectors are leaking? I'm going to be sending those off to be cleaned, so hopefully that will help. But how else does so much gas and carbon crap get in the intake?

Also, put brand new plugs in and after just letting the car idle for a little bit, the plugs are already turning black with carbon crap on them. Man, what's going on here?

Any help on this would be appreciated.

 

I also had tons of carbon in my intake

 

Im pretty sure its normal. I had carbon build up when i took my intake off. Carbon through all the runners.

 

Dumping some engine cleaner in your gas tank when you fill it every once in a while cleans that out. Also taking it on LONG highway miles or even Dragracing it will clean it out.

 

It's partly unburnt fuel from the EGR system, partly oil residue from the PCV system, and partly dirt that gets past the air and fuel filters. I don't think I've ever seen a street engine that didn't get carbon buildup...it's really very normal. Keeping the PCV and fuel filter changed helps, as well as running an intake cleaner through it periodically.

 

damn emmissions systems clogging up youre engines!

 

Not mine.

 

GreatJ hit it on the head. The combination of the stock EGR and PCV systems gums up the works pretty quick on old TPI engines. I've seen this many times. There's a reason that factory TPI throttle bodies have an anti-carbon-stick coating on the backs of the throttle blades. The rest of the intake system is fair game for the stuck-on black sticky stuff, though.

Gotta clean it out manually. Fuel injection additives squirt out through the injectors which are WAY downstream of the TB area on a TPI intake.

 

They do have some stuff that sprays into the TB to clean the hell out of it but the only think I would be concerned is the TB and the IAT instead of the entire plenum.