Hi,
I got an opinion on my 98 GEMS P38 Range Rover regarding the throttle body assembly. The dealership says it needs to be replaced. Will cleaning it make it work? There have been low idle/stalling issues. It seems to be the right diagnosis, but I need to know either way based on your experience. Thanks.

Matt

 

The throttle body can easily be cleaned by a DIY, the large butterfly valve can be cleaned with carb cleaner spray and even a small soft brush if desired. There are also going to be other ports on the body where hose attach to bring PCV vapors or supply air to the PCV system, these can also be cleaned out. The Idle Air Control Valve (IACV) can be removed, spray cleaned with carb cleaner (don't physically move the tip), and the bore it fits in also cleaned with carb cleaner.

If you peer into the open end of the throttle body (remove MAF hose) it should be clean metal, not black or sludged.

The throttle body simply moves air, fuel is sprayed into engine further along. The dirt and gunk in the throttle body can make the butterfly valve stick. Build up from the PCV can block other passages. The IACV controls idle, it is a 200 step computer controlled vacuum leak. A very worn throttle body might have a ridge you can feel that the butterfly valve sticks in (unusual). The throttle linkange can bind (and can be lubed). IMHO try a can of carb cleaner first. Engine will crank strangely at first, as extra fuel not commanded by the computer is present. I have cleaned mine on a D1 with 175K plus, and the throttle body is not worn out yet. It is just a chunk of precision made metal. Not a lot of parts to wear, but a good many to be gunked up.

Also check air fliter (have you ever changed it?), air box lid (latched), and MAF sensor and rubber hose (no cracks). The MAF sensor is very costly, but can be cleaned if needed with a spray made for the purpose (not carb cleaner). Only do this when the engine is stone cold, don't even switch on radio. When truck powers up, a spot inside the MAF is heated to 350F plus. Hit that will a cold stream of cleaner and it can crack the internal elements.