Welcome !
I can only answer 3rd question in some respects .Being an earlier model ,your tranny might hurt if you abuse your car jusr like red lining by using your sport mode .I would never do that but that might be only me

 

Sorry cant help on the first two.
Re the sposts mode?....By all means have some fun with it now n then but use it continually and yeah, I'm sure it won't do any good whatsoever, apart from which your gas mileage will drop like a stone.

Jim

 

Pics of the first two so that we may better help you. As for #3, the tranny is weak, so be nice to her. Treat her like a hoe and beat her once in a while when you feel the urge, but don't take her home and bang her every night. Also, gas mileage will go down the drain in sports mode.

 

Nice one, bigdreams...

Q #2, sounds like the interior light just popped out of its holder. Your gonna have to squeeze your big head in there and reinsert it...

 

Welcome good luck fixing your problems...like the analogy bigs but since when do you talk like that?
Don't even bother with the sport mode I personally like the j-gate it does the same thing but with more interaction and control on your part!

 

Hi Guys,

Im new here, so please forgive. Posting here because I'm not even sure how to open my own new post.

We have a '03 Jag x400 (3.0L V6) and there are a few things I would like to sort out.

A) The alternator light keeps coming on, mostly a few minutes after being started and it stays on. Apparently the alternator is over charging. I has been to auto electricians and has had a new alternator fitted, light still comes on.

B) Gas milage seems down the drain. If the sports mode button is pressed, it lights up, but does nothing to RPM or driving feel. Could it actually be stuck in sports mode?
What is the sports mode supposed to do? We have a 540i BM and when pushed into sports mode you can see the revs jump. Does the x400 work on the same pricipal?

C) At cold start up idle is very rough and irregular and sometimes dies and has to be restarted.

 

Hi Guys,

Im new here, so please forgive.

We have a '03 Jag x400 (3.0L V6) and there are a few things I would like to sort out.

A) The alternator light keeps coming on, mostly a few minutes after being started and it stays on. Apparently the alternator is over charging. I has been to auto electricians and has had a new alternator fitted, light still comes on.

B) Gas milage seems down the drain. If the sports mode button is pressed, it lights up, but does nothing to RPM or driving feel. Could it actually be stuck in sports mode?
What is the sports mode supposed to do? We have a 540i BM and when pushed into sports mode you can see the revs jump. Does the x400 work on the same pricipal?

C) At cold start up idle is very rough and irregular and sometimes dies and has to be restarted.

 

jagx400, welcome to the site. I think you will like it here. Lots of good knowledge to be shared here and people more than willing to share it.

As for problem A. From the sounds of things, your problem is coming from the sensing wire. There is a high resistance in it and that is causing the computer to see a lower than normal voltage which then makes the computer attempt to raise the voltage in your car to correct for this "lower" voltage. A quality shop should be able to diagnose that in no time flat.

As for question B. Sports mode is a function that adjusts the shift points of the tranny based on how the car is being driven. With the light off, Sports Mode is turned off. So, you have normal shift points. With the Sports Mode turned on (ie, red light on the center console next to the "S" button), if you step on the gas to make the car rev up to say 5,000 RPM with Sport Mode off, it will now go up to say 5,500 RPM. But, if you were to lower that down to say 3,000 RPM (Sport Mode off), it may only shift now at 3,300. So, the higher shift point is a function of how much gas you are using. As for Sport Mode causing mileage to drop, I leave Sport Mode ON all the time. I still pull 26-27 MPG on the highway with ease. If you drive easy, you may find that it will help the mileage some as you are allowing the engine to shift a little higher, which is going to keep the engine more in the power band, letting it perform in a more efficient region. Most probably see the mileage drop when using sport mode because they are taking the engine up to 5,000 to 6,000 RPM which is pushing the motor way out of any efficiency point.

As for question C. This can be caused by a few things. First off, I would start with cleaning the throttlebody out with some throttlebody cleaner (not carb cleaner). If you see a brown stain on the inside of the throttlebody, squirt it with the throttlebody cleaner. You may need to manually open the butterfly valve with your finger so you can get inside too and also on the edges of the metal disk. After that, do a look over of the vacuum line running from the intake to the brake booster. See if you spot any cracks in that line. Then, if you look to the left of the throttlebody, there will be a large hose that runs from the intake to the front valve cover. Check the underside of that hose. This is known to split and it will cause all sorts of havoc with the car.

 

Hi Chris,

Thanks so much for that really really long response!

We actually took our BM to the auto electrician for something and that is where we saw the Jag. The guy mentioned how it has been by them for a while because of the alternator light, and they can't seem to get it to go out. They basically stripped the car trying to find the problem (And actually caused lots of untidyness. Wires were not tied up, closed up, bound etc. So the engine wiring looks quite untidy now as opposed to how it should look.)

Silly question, but could you please clarify what leads/wires i need to check for the problem? Would it be found from alternator to battery? Or battery to ECM?

Not doubting you, but I read the following somewhere.

A guy had the same problem on his x400, Jag put in 3 new alternators, still the light kept coming on. Then an auto boff said its not a problem with the wiring, or the alternator, but with the ECM. On an auto, the alternator has an "electronic clutch".
When the car is started, initial voltage drain is high, so the ECM sends a signal for the alternator clutch to change to a "high voltage". When the ECM sees the car has warmed up, it sends a signal to the alternator to change down to a lower voltage. According to this guy, the ECM is not picking up that the car is now warm etc and needs to lower its voltage, hence the overcharging and continueous battery light. This really makes sense to me, should the alternator actually have a ECM determined output voltage. How does this sound to you? And, if this is the case, how would this be fixed? A new ECM? Reloading software?

By the way, now that I think of it, if the ECM signals the alternator according to engine temperature, could this not be why the car actually does not idle properly in the first place? Maybe the temp sensor that the ECM needs to adjust voltage and idle speed is actually stuffed?

Ps, if i am not mistaken, if a battery is continueously overcharged, it will not last very long, it will become dry, and it will swell. Is this correct? Because the battery is fine, water level 100%, and cranks strongly every time. No problem and its the same battery since we bought it standing at the auto elec ( a few months ago )
So is this a "fake" battery light? Not overchanging and not undercharging, however lighting up?

I am just throwing idea so please don't shoot me! : )

Ps, the breather pipe across the top of engine was superglued around the end by whoever messed with it last. Cant find a new one so fived it up pretty well, however car still does not idle on cold startup. That break booster one way valve has seen its days, its white and cracked, however there seems to be no leak or "hiss".
I have read this car is known for having leaks on the intake man gasket or something.
I will however do as you said and recheck pipes, clean throttle etc and let you know.

I do appreciate your assistance very much.

 

Welcome to the forum jagx400,

To start your own post, click on the New Thread button top left of the list of threads.

Thermo has already picked up on your issues in this one so it might as well stay here.

Please also post in the New Member Area - Intro a MUST to introduce yourself and your X-Type to all the members.

Graham

 

jagx400, when it comes to the initial charging of the battery after start, you have the idea correct, but there is no clutch with the alternator. What happens is the ECM sees the car start and then for a finite period of time after the car is started, it will artificially raise the voltage to make up for the losses starting the car. This is all done by affecting the amount of voltage going to the field windings of the alternator.

TO prove that the alternator is overcharging the car, what I want you to do is to get your hands on a multimeter. Now, set the multimeter to the "VDC" range and make sure that it can read up to 20 VDC (normally will have an "AUTO" range or the dial will say something to the effect of "2VDC", "20VDC", "200VDC"). Connect the red lead to the positive terminal of the battery and the black lead to the negative terminal of the battery. With the engine off, you should be seeing 12.6 VDC (if it is at 12.5 VDC or lower, then you have a battery issue - highly unlikely in this situation based on what you are saying). With the aide of a second person, start the car. You should see the multimeter ramp up and go to about 14.4 VDC, hang there for about a minute or so and then ramp down over a few seconds to 13.7 VDC. If you happen to see the multimeter ramp up to around 15.0 VDC and then down to 14.4 VDC, then let me know. If the multimeter is at 13.7 VDC and the battery light is on, then you have a problem most likely inside the dash. If the voltage ramps up to 14.4 VDC right after starting the car and then never comes down, then odds are you have a problem with the ECM.

HOpe this helps.

 

Hey Chris,

Ok, went to buy a digital multi because i couldn't find the old school one.

Anyway, below is the voltage kind of averaged out, it jumped around by point digits, so not sure if that is normal? For eg 13.2, 13.3, 13.2, 13.4, 13.7, 13,2 and thats how it would go. I know you said 12.5 or lower is a shot battery, but at times with the car off I was getting 13.1

These figures are from one attempt:
Dash Multi
Car Off 12.2 12.5
Car Started 13-14 14.6
After a few sec 14.4 14.9

The voltage seems to stay at 14.9, even at hot idle.

You said to let you know if it ramps to 15.0 and then 14.4, what then?
What could that be?

It is definitely not the actual alternator. They swopped it out with a new one and the light was still coming up, so its anywhere from the plug of the alternator. Where the exact problem is, is anyones guess.

Are there any diagnostic codes for charge faults chat could pinpoint the area of concern or even narrow it down? I have see P### codes on lists that touch on charge system.

Need to get it sorted as they won't pass roadworthy with the light on.
Plus my dad is convinced the wiring is going to go up in flames!

Really Really REALLY tired of this fault.

If it's the ECM, does it have to be replaced or software reloaded?
If it's the dash, do we need a new cluster?

About to push it off the cliff!

 

jagx400, not to get too technical on you (as you are not a wiring guy), some multimeters read the average of the wavering voltage, some read the peak voltage. In the case of our cars, the actual "DC" voltage is an average of 13.7 VDC, but it will jump between 13.0 and 14.4 in actuality. It does it really fast, so, to the eye, you do not see the fluctuations, but they are there. hence why when you have problems with the filter in the alternator, you will start seeing all sorts of strange things as the voltage now starts jumping between about 12.3 and 14.4 volts. This little bit extra really takes the computers and tosses them on their heads.

Because you are seeing 14.9 VDC and it is steady there, that is telling me that the ECM has a problem or there is a wiring issue. Because the voltage drops to around 13.X initially and then goes up to 14.9, I can be fairly certain it is not a wiring issue. So, that pretty much tells me that you have an ECM issue. I would recommend spending the few extra dollars to have a shop confirm that before you just start swapping out parts "just because". The ECM will also need to be flashed with the necessary data to make it talk with the rest of the car. So, this isn't something that you can do in your driveway (unless someone else can prove me wrong).