This was suggested as an FAQ by Jason/MoJ as a PM reply to him yesterday.
Here's a synopsis - hope it's OK if I'm brief:
Get fuel injection cleaner spray (not carb cleaner as it's too harsh), and have an old toothbrush (heat and bend brush part 30 degrees toward direction bristles point) and some clean rags on hand. Park truck on as steep an angle leaning to the right as possible (helps cleaner/crud run out of throttle body intake). Removen rubber tube connecting throttle body to air cleaner (helps to remove air cleaner and go easy on this ribbed tube so you don't crack it in the ribbed area).
Prop throttle valve fully open (I used a vise grip) and sparingly spray cleaner in and on the butterfly valve itself. The objective is to clean the grundge you'll find all around the edges of the valve itself, AND where these edges seat when it's closed. Those are the two most important surfaces and really the whole ball game. Alternately wipe with the rags and brush as much of these surfaces as you can until you don't seem to be getting any more of these oily deposits out. Forgot - put a rag where the cleaner fluid will drip onto the engine. Once done, you'll find that the valve will close with a crisp metallic "clack" rather than silently onto the oily deposits. If you feel you're getting a lot of the fluid deep into the intake, be mindful it's going into the cylinder and valves and thence a bit into the engine oil, so perhaps good to plan at the same time as an oil change afterward. Good luck!
DougM
Here's a synopsis - hope it's OK if I'm brief:
Get fuel injection cleaner spray (not carb cleaner as it's too harsh), and have an old toothbrush (heat and bend brush part 30 degrees toward direction bristles point) and some clean rags on hand. Park truck on as steep an angle leaning to the right as possible (helps cleaner/crud run out of throttle body intake). Removen rubber tube connecting throttle body to air cleaner (helps to remove air cleaner and go easy on this ribbed tube so you don't crack it in the ribbed area).
Prop throttle valve fully open (I used a vise grip) and sparingly spray cleaner in and on the butterfly valve itself. The objective is to clean the grundge you'll find all around the edges of the valve itself, AND where these edges seat when it's closed. Those are the two most important surfaces and really the whole ball game. Alternately wipe with the rags and brush as much of these surfaces as you can until you don't seem to be getting any more of these oily deposits out. Forgot - put a rag where the cleaner fluid will drip onto the engine. Once done, you'll find that the valve will close with a crisp metallic "clack" rather than silently onto the oily deposits. If you feel you're getting a lot of the fluid deep into the intake, be mindful it's going into the cylinder and valves and thence a bit into the engine oil, so perhaps good to plan at the same time as an oil change afterward. Good luck!
DougM