I'm wondering this, because I just did mine, but shining a light into the plenum reveals a dark and spooky cave of buildup. So, what effect is there in the advice to clean just the throttle body? To help the plate move freely? Is airflow affected by the slope grade down into the plenum? It's hard to see the point of this operation when the whole innards seem like they might be caked. My understanding though is that a seafoam ordeal can do a lot for the caked buildup?

I'm just wanting to understand my truck.

 

mine was so bad on my 85 4runner the only thing that cleaned it was i took it to a shop and they put it in there ultrasonic tank for 24hours it came out almost like bran new.. oh , sorry I took my plenum tank in for this service not the throt body

 

It depends on how much buildup you're talking about. If there is large amount of buildup, Seafoam will do little to nothing. Take the throttle body off and give it a thorough cleaning.

 

Carbon build up will affect airflow thru the throttle body but not enough to where you will notice it, unless, its horendously caked and impedes airflow across the throttle blade. Minor buildup in the plenum is normal, its difficult to detect a drivebility issue related to carbon coating. Again, it would have to be heavily coated to where it actually reduces interior volume at a measurable level.

Seafoam will clean it up, follow the directions on the can.

 

I have had cars that will throw CEL's because the buildup on the throttle plate will make it stick and not allow it to close all the way affecting the base idle and the TPS readings, this of course is on newer cars that have smaller tolerances for everything than our old trucks do, but still I believe that a clean TB will be noticable after driving around with a dirty one for a while.

 

The build up is in just more then your Plenum. You probably have some plugged lines and hoses in worse case scenario. I blocked off the EGR on my 88 build and have it listed on my 88s build. It is alot easier to pull it off and take the Plenum to the carwash and get the carbon out. Just remove your Throttle Position Sensor before washing.

Seafoam wouldnt do much to clean carbon out. It not to difficult to remove and clean.

 

Okay, I have a rough idle situation too. I picked up an intake gasket set - when I take it all apart to clean things, do I need a sticky product to apply with the gasket materials, or do they just get positioned in place?

Also what is the cause of say a quarter inch of this black sticky buildup in the intake over 15 years or so?

 

Typically gaskets go on dry. You can use rubber cement or 3M spray adhesive if you choose. Everybody has their own solutions to attaching gaskets on vertical and inverted surfaces. I've always set my gaskets dry. The key is a properly prepped surface for the gasket to seal to.

Also do not overtorque the mounting bolts as this could displace the gasket and cause potential leaks.