When attempting to clean my throttle body out again, I noticed the engine side of the butterfly valve is coated in black in comparison to the brass color on the opposite side, and won't rub off with the throttle cleaner spray. I scraped just a tiny bit to reveal the brass color underneath it. This may be a dumb question, but the black is not a "special coating" or anything like that, is it? If it's build-up gunk, can you just scrub it off? Before I go any further, I want to make sure I'm not messing anything up. I know the manuals say there's a special coating on the throttle body. So basically, should the other side of the valve be the same shiny brass color as the front side?

 

I could be wrong but I thought they are not allowed to clean the inside of throttle body because of the coating.

 

It's Moly grease and it belongs there. Jaguar specifically notes to leave it. If you remove it, You would have to replace it.

 

I ended up pulling the throttle body out of the car so I can really take a look at it. The black stuff definitely was not moly grease. It was old caked on oil vapor gunk. Got it all off and car is accelerating much smoother now. I'm not convinced their "special coating" is anything more than a gimmick forcing you to buy an entirely new throttle body whenever it gets dirty, not unlike when the position sensor freaks out. We'll see what happens.

 

Maybe you are right. How did you clean it? Did you use the throttle body cleaner or just simply wipe it off? Thanks!

 

I used throttle body cleaner that says its safe for factory coatings, rags, and a toothbrush. That gunk was on there real good. It took a lot of elbow grease to get it off.

 

I think you are right because it will get dirty anyway after a long term use regardless the coating, and if it is not allowed to clean it, then what will be happened? It reminds me their ZF transmission was suppose to sealed for "life" but you'd better to replace the fluid before the life is over.

 

Sorry, maybe not specifically Moly but it is a protective film and is there to prevent build up of gun in the throttle body. It's used on Ford vehicles and probably why it was used on your Jag as it was built by Ford.

I bought a 3M throttle body/ injector cleaning kit that, like the manual, said if it's there, leave it on. If you've removed it, I think you'll just need to clean it more frequently, frequent being a relative term. Obviously it improved the performance of your vehicle.

From Popular Mechanics:
Some throttle body bores have a coating to reduce the buildup, but, in time, bores with protective coats can be affected. There are several ways to clean out the area. The best is with a professional tool called the Intake Snake, which comes with an effective yet safe solvent, and the simplest is with an old worn-out toothbrush with soft bristles and a mild solvent.

There are three reasons why you have to be careful, both in choice of solvent and in application: First, if the throttle body has a protective coating (as on many Ford products) to reduce the buildup, a strong solvent and hard brushing will remove it, so you'd have to do the job more often. If you see a warning label on a Ford product, that's why.

 

Interesting, Sean. That makes a lot of sense. I guess I'll check and clean it more often from now on to be on the safe side. Thank you.

 

I have a used TB and when I cleaned it I found a black coating about 6mm wide around

the edge of the butterfly.

There is no coating on the TB other than this black coating which looks like a Molybdenum

Disulphide compound.

IMO there is no reason why the TB cannot be cleaned as long as this coating is not removed.

I have noted a recent post stating that after TB cleaning the 'Base Air' should be reset and it

cannot be done using SDD.

I wonder how essential this reset is?

 

I'm afraid I can't answer how essential the reset is, but so far my performance has improved considerably. It seems to be getting better actually. Last night when I test drove it, it felt quicker but not dramatically so. This morning was about the same. I did a quick lunchtime run today and the performance felt really sharp. Nice acceleration, better stopping, better idling; really impressive.

 

How many miles on your Jag? I have a same 2005 XJ8L with 53k miles.

 

You have answered my question then XJ8JR.

ie not essential at all!

 

Mine's coming up on 139k

 

Thank you!