Since we have electronic throttle body in our X350 and we need to have the key on and press the pedal down to let the butterfly valve to stay open while cleaning.

The question is, when it's in that key on mode and if I accident move the butterfly valve by accident and moved it to different postion than stock, will it screw the computer calibrate up or the computer will recalibrate itself to the correct position upon restart procedure?

Planning to do the throttle body cleaning this Sunday.

Thanks.

 

It has a spring to return it to closed position and uses PWM to drive the motor to open it up as needed. The sensor is attached to the shaft of the flap and measures the absolute position. It won't get miss-calibrated.

That said the throttle body sensor is one of the weak spots on these cars, so if you get "DSC failure, engine system failure, park brake failure" combo this is likely the problem.

 

I think the best way to clean the throttle body IMO is to remove it from the engine since most of the dirt will be on the engine side if the butterfly.

If you don't want to do that then I would ensure key off and move butterfly manually to clean. When doing this you can feel/hear the drive motor turning.

I have done this on a spare TB and I think it will not cause any damage.

 

I cleaned my TB yesterday as part of my ongoing diag. with a huge string of vehicle faults. Removed and cleaned the MAF and cleaned the TB. As stated above you can manually move the throttle and when doing so you will feel the drive motor, you let go of it and it will return to it's normal closed position. As a follow up I'm going to do full intake de-carb and intake cleaning. Something I've done on other vehicle's but not yet the XJ. At work we have a kit my MOC that contains a fuel tank additive, can of throttle body cleaner, and a bottle that will remove carbon from the intake and vales which is added using manifold vacuum. I'll try to update my results after doing so.

 

Well due to issue at work didn't manage to get it done this weekend. I don't have any issue but just wanted to clean it since I thought I have nothing to do over the weekend and last time when I have the upper intake elbow off I saw there is some build up that I just wanted to clean it off for the time being.

 

Can you PLEASE post some pictures? This is something I want to do as well.

 

Someone please help, I could not remove the throttle body pipe. Do i need to ply out the pipe from the throttle body?

 

Hi Jayson,

I'm not sure, but the answer may be in the X350 Workshop Manual, in the Powertrain section. You can download all six sections of the manual from the links below:

http://www.mediafire.com/download/md...f+contents.pdf
http://www.mediafire.com/download/aa...nformation.pdf
http://www.mediafire.com/download/n3...2.+Chassis.pdf
http://www.mediafire.com/download/9b...Powertrain.pdf
http://www.mediafire.com/download/0i...Electrical.pdf
http://www.mediafire.com/download/4j...+and+Paint.pdf


Please note the cautions in the manual against cleaning the throttle body and take care not to remove the special coating on the back of the butterfly plate.

Cheers,

Don

 

Thanks Don, I got the manual, and I followed it step by step. However, when I loosen the clamps, I used a lot force to try pull out the air intake pipe from the throttle body neck, it won't come off. I was wondering is there a specific sequence to remove as in the manual, it simply had an arrow pointing to the clamp, but didn't show any procedures thereafter.

 

I had this problem recently when I wanted to check the condition of the air filter.

It helped to take the resonator box off it's bracket but you have to be a bit

'tough' with it to get the pipe off the TB.

Try compressing the corrugated bit by pulling the pipe right back.

A bit of gentle heat from a hair drier will soften the corrugations.

 

Hi Jayson,

I can't help you with the throttle body end of the intake pipe that mounts on top of the engine - I haven't removed it on our car yet but intend to in the near future. From your description, I assumed you are talking about Part 4 in the attached parts diagram? If so, it certainly appears that it is secured only by the hose clamp, Part 9.

If instead you are talking about the pipe from the air filter housing to the intake pipe, Part 3 in the diagram, the photos at the links below may be helpful:

Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page


Please keep us informed,

Cheers,

Don

 

I'm not sure why, but a lot of Jaguar specialists advise against cleaning the butterfly on an x350. This is in comparison to an x308 where it was almost a recommended procedure. I think the concerns stem from the fact that there are more electronics controlling its position etc.

I cleaned mine in an attempt to cure a spurious MAF fault which was bringing on the MIL almost daily. The clean seemed to have cured the problem but the car seems to have now forgotten its idle speed from cold. It starts at 1400 rpm and gradually drops down to correct idle after 5 minutes. It never did this before. I have been given a procedure to reteach the car what should be 100% throttle and normal idle speed but haven't got a round to doing it yet.

Paul

 

Hi Paul,

The reason Jaguar dealers and specialists advise against cleaning the TB on an X350 is that there is a special coating and the X350 Workshop Manual specifically states that the TB should not be cleaned to prevent damage to this coating.

The warning appears several times throughout the manual. Here's the warning from the Throttle Body section for our XJR:

CAUTION: Do not attempt to clean the throttle body. The bore and the throttle plate has [sic] a special coating applied during manufacture which should not be removed.


The other issue is that, if I understand correctly, the butterfly valve is operated by an electric motor and it is apparenlty easy to get things out of adjustment when disturbing the TB.

Cheers,

Don

 

Thanks guys on all the ideas and description. In regards to Don, yes, I am talking about part 4, and the hose clamp(9), it's already tough enough to loosen and retightening that clamp. I will try again to see if I can use a little leverage and gently ply it out with a little heating like Meirion indicated but there are sure lots of electrical wires in that area! Wish me luck, thanks guys.

 

Sorry but I only have part 2 and parts 7 on my 3.5l engine but maybe some of my

advice is still valid.

 

Thanks guys! I finally were able to remove the air intake pipe from the throttle body. There are actually 2 clamps, and you have to look closely because 1 for connecting to the throttle body neck, and the other one to the air intake itself. You want to remove the clamp that is secured to the throttle body. Don't be like me, I felt like a fool for trying so hard to ply it out. I am currently cleaning the butterfly, and notice a lot of gummy stuff is on the side wall underneath it. I will update you guys if the code P0101 is gone. Anyhow, thanks again for all the help and encouragement.

 

After cleaning the throttle body, I reassemble air intake system back and let it seat for a couple of hour so all the solvent can dry up before I try to start the engine. It took a few turn to start the engine, but it finally started. When I apply gas to rev the RPM to 2500, I notice that the RPM drop back to 1200, and from there take 3-4 seconds hesitation before going back to around 600rpm. Anyhow, I drove the car for 25 miles on the highway, it was fine. But when I take it locally, the hesitation is very irritating. It seem as the throttle body is a little sticky. After which I drove another 10 miles are so, CIL went on with a code of P0171 and P0175, and from the live data, I notice my long term fuel trim will not go under -12.5. I read in the forum, it be a good idea to give the throttle body a little WD-40 for lubrication. I have a feeling it is the throttle body, that is the problem, but not really sure. Any suggestion to what my next steps in resolving these issues will be very appreciated.

 

Jayson,

That is a very odd combination of codes. P0171 indicates "Right-hand cylinders combustion too lean," and P0175 indicates "Left-hand cylinders combustion too rich." I'm not sure I can recall ever seeing that before.

Is it possible that your P0175 code is actually P0174 ("Left-hand cylinders combustion too lean")? If so, I would suspect an air leak in the air intake plumbing between the MAFS and the cylinder head, allowing unmetered air into the system and causing all cylinders to run lean. Given the work you've just done, a likely suspect for a leak would be at one of the joints in the air intake pipes you disconnected between the air filter housing and the throttle body (Parts 3 and 4 in the diagram in my earlier post). Another common leak point is the throttle body gasket.

BTW, you can look up the possible causes of any Diagnostic Trouble Code (DTC) in the X350 Workshop Manual, which can be downloaded at the links I posted earlier. The P codes are in the Powertrain section, C codes in the Chassis section, B codes in the Body section, and U (Undefined) codes are in the Electrical section.

Please keep us informed.

Cheers,

Don

 

I think U are Network codes though why they're not N I don't know.

 

I don't know either. Most if not all of the U codes have to do with one network or another (CAN, ISO, D2B, etc.). My assumption is that when the OBDII standard was being developed in the early '90s, the U codes were left "Undefined" so manufacturers could define them in the context of their own proprietary implementations at their discretion.

Hopefully one of our members can educate us.

Cheers,

Don