Hey guys, so I noticed that for some reason, my dad's Jaguar doesn't seem to be idling at one spot, instead it jumps up and down as seen in this video:
Now I do notice that some carbon deposit is present in the throttle body, should I clean it up? And I noticed that it is not really as "mechanical" as other cars (There's no way to move the flap unless if you directly touch it, while other car you can open/close it easily since there's a lever outside of the TB that allows you to move the flap).

Also is there any other thing that may add up to this little issue? If so then please let me know >

Thanks.

 

Sounds fine to me, from what i heard, have the spark plugs been changed?

 

Idle air valve acting up a little.

 

I don’t think it has ever been changed.

 

Oh really?

 

Their first called for change is @ 100,000 miles.

Changed mine out a little before that, with new coils from China.

 

Alright, so after finding out that the ETB flap can be opened using the gas pedal while on the 3rd position, we cleaned it with a throttle body cleaner, and well, things starts to get a bit worse...
When we started it up, it had a pause before fully compressed/started up and it started with a "CLANG CLANG" noise, following by a squeak which were gone, and although the idle seems to sit at one spot, the check engine light was on.
Also it wouldn't start without the air filter + assembly (It started without it when we were doing the serpentine belt/pulley job).
Anyway, things came back to a "normal" state when my dad unplugged the TPS and plugged it back it (Which turned the check engine light off), idle is back to where it was (As seen on the vid).
So what do you guys think? Should we buy a OBD2 scanner to clear the code? (Because it may still be stored in the computer).

 

A Jaguar specific reader is a must to have, to read, & clear the different codes

 

That very slight rpm needle movement is normal. Don't give it another thought.

 

Mine does not hunt at idle - yet!

 

Hi Tom,

My first recommendation would be to make a small investment in the DashCommand app and an ELM327 WiFi OBDII adapter for iPhone, or the Torque Pro app and an ELM327 Bluetooth OBDII adapter for Android. Around $20.00 for both (search eBay for ELM327 adapters). With this setup, you can scan and clear Powertrain diagnostic trouble codes with your phone, and you can also view Live Data. If you will view the Short Term Fuel Trims (STFT) and Long Term Fuel Trims (LTFT), you will know whether the engine is running lean or rich. There are lots of places your engine can develop air leaks, which lead to lean running and unstable idle speeds. The X350 engines are typically very smooth and stable at idle.

Regarding the throttle body, Jaguar advises against cleaning it due to the risk of contaminating the Throttle Position Sensor/Throttle Motor with cleaning solvent. I do clean them, but take care not to get excessive solvent around the ends of the shaft where it could seep into the sensor/motor assembly.

The Mass Air Flow Sensor (MAFS) is mounted in the air intake pipe close to the air filter housing. It is a critical engine management system sensor, and your engine may or may not start if it is disconnected or not in the path of the air being inhaled by the engine.

Cheers,

Don

 

Hey Don! Thanks for your answer.
About the OBDII scanner, would it be able to reset the Throttle Position Sensor values? Is it reliable (As in not losing connections while running a scan)?.
About the ETB, we never know about any of that assuming that it's all fine as long as we don't touch the butterfly flaps (But yea, maybe we messed up something, and the idle only returns to the beginning state seen in the vid when my dad disconnect the TPS and reconnect it).
About the MAFS, yea that would make sense, but I recalled that the engine started with a "Restricted Performance" message, maybe only on that occasion it wouldn't start due to us cleaning the ETB and messing up the value (I'm not entirely sure since I had responsibility to held the gas pedal, so I really can't tell what was going on while my dad cleaned it).
Also after that event, I'm quite worried about the engine health/condition (The first time we started up the engine after cleaning up, it sounded like a tractor, making a ton of clunking/tapping noise, which reappear on one occasion when we were about to take a bit of a trip. The belt squeaked again for unknown reason, rendering 4-6 hours of replacing it and the pulley useless). We're not sure about what's going to come, but sometimes, it's just unexpected (Recently, my dad turned the AC on and the engine stalled randomly, even though the battery was in good shape). Do you think if there's any sort of issue happening with the engine itself?
I really appreciate your detailed answer, but do you think if you can help us out once again? Especially since it's the main family car that my parents take to work every day.
Please reply ASAP.
Thank you.
(I do apologize if some of things aren't making much sense, it's a bit of stress and my bad English).

 

Hi Tom,

Yes, the inexpensive scan setups I mentioned are reliable and losing the bluetooth or WiFi connection while scanning is rarely an issue and of no consequence if it occurs since scanning codes is a unidirectional function and cannot damage the car. As with any scan tool, you do need to take care when inserting the OBDII adapter in the Data Link Connector to avoid bending any connector pins and potentially shorting pins together.


It just dawned on me that if you were opening the throttle plate by holding the gas pedal to the floor, you must have had the ignition switched on. It is never wise to clean critical components, or to disconnect sensors or other components, while they are powered.


It is quite likely that the engine was misfiring as the cleaning solvent used on the throttle body caused excessively rich running in some or all cylinders. However, I'm not happy to hear that this clunking/tapping occurred on another occasion apart from the throttle body cleaning. Are you keeping the engine oil topped up and using the correct viscosity and type of oil, and are you changing the oil at proper intervals (3,000 miles for conventional, 5,000 miles for synthetic)?


Belts can squeak for many reasons. Condensation, oil contamination, coolant from a leak, a failing and intermittently seized bearing on one of the belt-driven components, etc. When you had the belt off, did you spin the pulleys on all of the belt-driven components to check for bearing roughness or play?

Cheers,

Don

 

Hey Don, first of all, sorry for the late answer, it's been a busy week, and second, thanks for your answer once again.

About the first question: Sweet! But I'm still considering that and this scanner that I've found on Amazon: . Should I go with the ELM327 or this one?

About the second question: Yes, I did put the ignition to the 3rd position which allows the butterfly flaps to open. Also about the sensor, well we didn't know that it's bad to disconnect it while the battery is still connected (Maybe next time it's better to disconnect the battery, I think that's a lesson learned :v).

About the third question: Yup, seems like that is the issue (Because I recall my dad cleaning it 6 times to get all the carbon deposits off, which would lead to many of it going into the TB, causing a misfire). About the other occasion, I've just remembered that despite it sound quite clunking, it's more of a sound of something stuck in the way of another moving part (Which is weird, considering the fact that we cleared everything off, so nothing could get in the way). About the oil change, I think that we should replace it (34,269 miles at purchase --> 38,800 miles at the moment = Around 4,500 miles)

About the fourth question: Yes, my dad checked all the pulley while we had the belt off, and it's all good. Also no leaks, no anything, and when we clean the Throttle Body, we had covered the body with rags, so when the cleaner came off, the rag would absorb it.
Honestly it's funny that the squeak came back when we cleaned the Throttle Body, but before that, it was all quiet, even starting in cold weather condition, it wouldn't squeak at all.

About the car: It's been some time after that, and despite the fact that it runs fine, I'm still quite worried about it.

Anyway, hopefully we can find the issues and fix it so we wouldn't have to worry much again.

Thanks.
Tom.

 

Funnily enough yes. The workshop manual actually lists that as a possibility, even though the X350 4.2 does not have one. When one goes to the possible corrections it lists all the usual, such as air leaks etc.

 

Well, that could be a possibility.
Anyway first thing to do is to get an OBD2 scanner that can clear codes/troubleshoot things before moving onto that case.
Honestly I'm quite worried about the idle, especially when stopping at the red light, you can feel the engine rev goes down and up.

 

As a matter of interest - does it always do the low rev and back to normal when coming to a red light? Or is it only sometimes? If you let your foot off the gas quickly the car cuts off fuel, to give engine braking, since it figures you want to stop. It is supposed to cut it back in so the revs do not fall below normal. If you sneak up to the red light with a slow release of throttle, and then brake, the fuel is not cut off. Try that and see if it is only doing it on one scenario.

 

When stopping at a red light, yes. You can really feel the engine speed going up and down, up and down, up and down...
Also about your second question, well my dad's way of driving is gentle, so yea, he did almost what you said when you're talking the fuel not cutting off. Sadly, the idle seems to keep "hunting".

 

OK that narrows it down a little. Could not remember if I had mentioned the TSB for the hunting idle. The fix in that case was to do a professional injector clean service, under warranty at that time.

 

Well I don't really know if the original owner of this car have that issue (We have the car for almost a year now).
Also about the injector, should we buy injector cleaner and put that in the gas?