The check engine light is on, on my 2005 STR, I have less than 88k miles on it. Jaguar says that the throttle body, gasket, and O2 sensors need to be replaced. My mechanic told me that the gasket for the throttle body might be bad because there's a hissing type sound under the hood. I agree that the gasket for the throttle body would be bad, but disagree that the throttle body is bad, it probably needs a good cleaning. I told my mechanic that the code I have on the check engine light is the infamous O2 sensor code. He told me that it would be best to change the gasket first since it might be the cause to trigger the code. Does anyone know the part number for the throttle body gasket?

 

From JEPC

AJ83445 for the 4.2 S/C

 

What codes are set?

Did your mechanic actually locate the source of the hissing sound?

It could be one of the vacuum lines has a hole in it. It should be a fairly easy find. Find a length of 1/2" - 1/4" hose. Put one end to your ear and run the other end around the throttle body and other hoses. You should hear the leak when you get close.

 

I'll have to rescan the car for to tell you the code that came up. I looked up the code and every where I looked it up it said O2 sensor.

 

Are you planning to clean the throttle body before considering removal? I know that cleaning these is pretty commonly done howeve I've seen cautions about damaging seals, etc. It might be safer to clean it after removal. Mine is currently removed and on the bench and it is certainly dirty, quite black on the underside of the plate.

 

The warning about not cleaning it is because of the internal coating on the throttle body. Most cleaners remove this coating and it's not a big deal but the coating is there to help reduce the buildup of dirt.

So if you remove the coating the throttle body will build dirt on its inner surfaces faster. Now I have cleaned and removed a bunch of these coatings in the past and I can't say I noticed the dirt building up any faster but that is the explanation.

Nothing to do with the seals? Now you can get throttle body safe cleaner which is supposed to remove the dirt buildup without removing the coating. I can't say how well that works.
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I would think if you had a leak bad enough that it produces a sound it would throw a code. I would get a second opinion! As for cleaning the throttle body use a throttle body cleaner and I use CRC. Now you hear a lot about the coating on the throttle body and that should not be a concern as long as you do not scrub it with a brush. MANY of us have been cleaning the throttle bodies with no repercussions. As for the O2 what was that code. We like codes not what they mean.

Link to how I clean the TB JagRepair.com - Jaguar Repair Information Resource

 

What exactly is the code? It could well be a dead O2 sensor, mine went this year and I replaced.

 

If you've got a hiss find where from and fix it, then see if O2 code returns.

Leave TB alone until the above is done.