The supercharger bypass valve on my 01 XJR isn't opening, and there's a sucking sound coming from an open hose attached to a harness end down behind the throttle body (see red arrow in attached photo). When I plug the end of the hose, the bypass valve closes. However there's nothing obvious the loose end should be connected to. The other end tucks under the left hand side of the throttle body and heads forward, I can't see where to.

Anyone know what the hose should be hooked to?

 

it should be connected to the MAP sensor, see this thread, I included a picture and diagram.
https://www.jaguarforums.com/forum/x...-sensor-90816/
hope this helps

 

Thanks Sean,

Where's the MAP supposed to live? I've found some pictures of one,and it looks like the unit in the centre right of your photo, sitting beside the wiper motor, just under the mounting bracket for the centre cover. Is that it? In which case, I don't have one on my car.

Any idea if the MAP sensor was standard fit for all XJRs? If not, maybe that hose is just supposed to be blanked off.

 

Yes, it's mounted to the bracket, it's a Denso unit and has a little nipple underneath you push the tube onto, my tube was loose so I cut it back 10mm and used a smaller zip tie.

As far as I know all R's have a MAP sensor...it won't throw a CEL if not connected so someone's been in there.....have a look for the 3 wire connector. Once you find the loom connector it's time to get the MAP plugged in.

You'll then enjoy the full power of the car. My question is why has it been removed?

 

If I were in a cynical mood I'd say "To hide the fact that the EGR's playing up". Which it has been since I bought the car. However it's been dealer serviced since new, and the previous owner didn't give the impression of being overly tech-savvy (not a tool in his garage when I went to try the car), so that's probably overly paranoid.

I actually don't think there's ever been a MAP sensor fitted. There's no paint damage where the bracket mounting screw should go (assuming the MAP sensor bracket attaches under the centre cover bracket), the grime underneath the centre cover bracket is evenly distributed without a clean patch where the MAP bracket would have been, and I can't see a loose lead, (although there are a couple of blanked off harness plugs nearby). Plus the hose is neatly cable tied to the wiring harness in such a way that it couldn't have stretched up to a MAP sensor. Lastly, the vac hose parts diagram shows a vac hose with a blanking plug (#21): I think this might be it, and the plug's just fallen off - I was messing around in that area recently replacing the EGR, and I've probably knocked it.

If one believes Wikipedia, a MAP sensor on a car which also has a MAF sensor is basically only there to check EGR function - I wonder if Jag saved themselves a few $$ by deleting it for markets with no emissions testing (like NZ).

At any rate, I've blanked the hose off and the car seems perfectly happy - sounds OK, grunt's OK, and it was doing 28MPG on a run this morning. I'll hook a reader up tomorrow and check fuel trims and codes, but barring that showing a problem I'll leave well enough alone.

Thanks for your help.

 

That could well be it, having only dealt with emission controlled UK cars I'm happy to go along with that assumption mine behaved well without it connected, apart from the slight hiss.

You can also blank off the EGR valve by using a couple of blanking plates, it saves crud going into the intercoolers.

 

Hi guys,

I'm a new forum member, although I've been reading these threads for a while now & they have helped me diagnose all manner of problems, so I must say thanks to all for the info that is posted on here..

I have a similar issue as to the one listed above. I have a running problem on my XKR and was reading this post thinking this may be my problem. Found the hose mentioned above and guess what? A bolt has been stuck in the end to cap it off?!

However I cannot find the MAP sensor either. There is a stud sticking out of the bulkhead in the position where the denzo unit is on the photo referenced in the above post, but thats it. (BTW this is a UK car, purchased from NI).

Any ideas? Seems from the above that the car will run without this MAP sensor anyway?

Problem I have is that the car won't rev correctly. If I hammer the throttle, it coughs and grunts, then will get to just short of 3000 rpm & then start hunting a missing. If I rev the car gently, it will get up to the same rpm smoothly & then behave the same way.

I've changed 4 coil packs, replaced plugs and am now starting to think that it isn't electrical, or ignition at any rate. The worst issue is that the car isn't throwing any fault codes! I know the fault code system is working, because I can remove plugs from sensors and it will throw me the correct code, but for this running problem I get nothing from the diagnostics.

If anyone has any ideas it would be massively appreciated!!

Cheers

Andy

 

Andy

With No codes... spark could be jumping from the boots to the engine

Does the engine appear to misfire while idleing? Also did you observe oil or fluid in the spark plug ports when you changed the plugs and put dielectric grease on the Coil/plug
boots?

 

Bigdadbear,

Thanks for the quick response.

There is no misfire upon idle, infact it starts 1st turn of the key & runs like a clock.... until I hit the throttle.

When I 1st went to change the plugs I did notice some water/oil residue down the nearside bank of 4 ports. I also noticed that the header tank had been replaced, which I thought was odd & made me a tad suspicious. This is the side where I have replaced the 4 coil packs, as these seemed in poor condition, albeit physical.

I've cleaned all that up now and there is no evidence of it returning (and I've changed 4 coil packs) thus far (taken some plugs out today and nothing seems out of place). All the plugs seem to have an even deposit on them. Its a black (ish) sooty deposit, but its equal on all 8 pots. This is what makes me think that it isn't an electrical issue. I wouldn't condsider myself an expert by any stretch, but I've done some methodical checks (isolating coil packs one at a time etc) and they all seem to be working.

its an odd one as its a pretty big misfire, a proper coughing / hunting episode and it doesn't go away - you can hold the throttle part way down and it will just hunt at around 2800 rpm. If you dump the throtle from idle it will cough and splutter, if you slowly build it up it will make its way to 2800 rpm smoothly and when it gets there, behave exactly the same way.

The grease you mention - didn't do this & its a new one on me. How does that work?

Cheers for your help.

Andy

 

Andy, are you talking about revving it in neutral, or while driving? Because in neutral there's a rev limiter which stops it going beyond 3000 rpm-odd. Not that that'll be affecting your low-rev problem, just might explain why it won't rev further.

I'd start by taking the MAF sensor off and giving the sensor wires a really good clean with MAF cleaner spray - MAFs can cause all sorts of grief, and it's a cheap thing to try first.

Failing that, what are the l/t and s/t fuel trims like, both at idle and when revving it in gear against the brake?

 

Hi Dave,

All of this is being done with the car parked - it isn't currently road legal so I cannot really drive it.

Regarding the rev limiter - seems like that may be half of my problem! Doh! But that's good, certainly reduces my list of problems!

So I guess now we have narrowed the fault down to a miss when I bury the throttle. If I slowly depress the throttle then the takeup is smooth. If I bury the throttle, it coughs and spluters before picking up.

I'll get some MAF cleaner and give that a go (although I've inspected it and it looks pretty clean). Is this MAF cleaner basically an electrical cleaner or is it more complex than that?

Not sure what you meant by "what are the l/t and s/t fuel trims like, both at idle and when revving it in gear against the brake" - is this the pressure to the 2 fuel rails??

Thanks for the help thus far.

Cheers,

Andy

 

Hi Andy
Update -- Info is on XJR - Looks like you have XKR - but the MAP sensor is the same.
http://www.partsgeek.com/catalog/200...ap_sensor.html

Here is what I found on the internet about pricing on the MAP sensor- there are a few UK sites that have it, but all seem to have same pricing. USA sites seem to have more mfg names parts available at lower prices.


SNG Barratt UK LNF1622AA £115.13 (£138.16) inc VAT

SNG Barratt - The Ultimate Jaguar Parts Specialist

Rock Auto Parts USA STANDARD MOTOR PRODUCTS Part # AS378 $171.79

2001 JAGUAR XJR Manifold Pressure (MAP) Sensor

Parts Greek USA MAP Sensor - Genuine W0133-1656925 $211.25

2000-2003 Jaguar Vanden Plas MAP Sensor - Genuine W0133-1656925 - - PartsGeek.com

Here is a JPEG showing for various mfg photos and prices on MAP sensor:

https://www.dropbox.com/s/80axy4tnnj...art%20info.jpg

Jim Lombardi

 

Hi Jim,

Thanks very much for that!

I spent most of yesterday looking around the vehicle for this unit and as per the posts near the top of this list, I'm not convinced that this was ever fitted to the car - There are no dirt or scuff marks around the mounting stud which would indicate that something was missing and more importantly, there is no electrical connector plug.

The consensus above seems to be that some vehicles were fitted with this MAP sensor and some were not, although I do find it odd (read unlikely!) that a bolt stuffed down the end of the vac tube would be a Jaguar factory fit?!

Cheers,

Andy

 

Andy
I just looked in the 1999 XK Electrical Guide - trying to find MAP sensor and realized that your 1999 XKR has an AJ26 SC engine and according to the Guide does not have a MAP sensor.

The 2000 XK Electrical Guide shows the AJ27 SC engine NA (North America) having the MAP Sensor wiring, but not the AJ27 SC engine ROW (Rest of the World).

It shows up on the 2001 XK Electrical Guide AJ27 SC engine - appears to be worldwide (no NA or ROW designation).

So it appears that the MAP sensor was not available on your 1999 XKR.

Jim Lombardi

 

Jim,

Thanks again!

So I can knock that of my list of possible issues.

Would a faulty knock sensor cause this type of running issue do you think? I'm hoping not as I've just been reading about how half the car needs to come apart in order to access it!

Again, I still have no codes & would expect a faulty sensor like that to throw up a fault code.

Cheers,

Andy

 

Looks clean doesn't necessarily mean is clean. Guess how I know. I'd guess MAF cleaner is basically electrical cleaner, but maybe with some additives - I just figure for the sake of a $10 can, better to use the "proper" stuff than regret it.

Long term and short term fuel trims are two of the PID readouts you should be able to get from your OBD reader (or rather 4 of them - the cylinder banks are separately measured). The engine management has a closed-loop fuel mixture adjustment based on O2 sensors in the exhaust, and the fuel trims are an indicator of how far it's having to adjust away from nominal to get the mixture right. If they're more than 5% or so away from zero, it's a pointer to something wrong: plenty of people here will likely pile in with suggestions if you post what you're seeing.

The readings can vary with engine rpm and load, depending on what's wrong: idle in neutral and revving in gear is just a quick and easy two points to look at. Long term trims are the main ones to look at, but don't totally ignore the short-term, especially if it's bouncing a lot in one direction.

There's a very good fuel trim tutorial somewhere in the stickies, but I can't find it to point you at it.

 

Hi Dave,

Thanks for the continued assistance - really appreciate it.

I'll get myself a can of MAF cleaner this week and give that a go.

As for the fuel trim data, I've just found the attached thread with some good info on:

https://www.jaguarforums.com/forum/g...ed-quiz-49317/

However I don't think my cheapo ebay code reader will supply me with this level of info:

U480 Any car OBD2 EOBD CAN BUS Fault Code Diagnostic Reader Scanner tool UK | eBay

(that isn't my actual unit, but has the same level of functionality).

Looks like I'm soon to be in the market for some software and a pc lead.....:-(

Cheers,

Andy

 

Good Evening All.

Thought I'd provide an update.

I have (at great insignificant cost!) procured a new ODBII reader and taken some readings at idle and also at circa 2300 rpm. Bear in mind this is all at standstill as the car isn't road legal (although once I sort this issue out I think it will be).

I have screen dumps for all of this but I haven't quite worked out how you are supposed to attach a file in here? Here goes, please let me know if this works:

file:///C:/Users/lovella/Desktop/XKR%20Data.pdf

Assuming you can read this attachment, I'd very much welcome anyone's assistance who might be able to interpret what all this means!! If you can't read the attachment could someone please give me some basic instruction??

Reading the above it would seem there is a problem as all the readings at idle are negative and are well in excess of 5% from Zero. At 2300 rpm the short term readings are +ve but the long terms are negative:

Idle

Bank 1 - Short term -11.7%, long term -15.6%
Bank 2 - Short term -12.5%, long term -15.6%

2300 RPM

Bank 1 - Short term +9.4%, long term -14.1%
Bank 2 - Short term +7.0%, long term -14.8%

Over to the clever people!!

Cheers,

Andy

P.S. the software that came with this diagnostic tool is proper winnets!! Damn thing crashes all the time and you have to minimise and then maximise the window in order to get the next screen shot - most annoying an un-user friendly. If anyone knows of a better download somewhere & could point me towards it that would be much appreciated.

 

From your figures there the idle speed short & long-term fuel trims are negative, indicating the ECU is reading a rich mixture & compensating by weakening the mixture.

The results at 2300rpm show a positive short-term reading, followed by a negative long-term reading. This would indicate the ECU richening the mixture as you 'snap' the throttle open to reach 2300rpm, then going negative on the long-term as the engine speed stabilises.

Both sets of readings are pointing towards a richer-then-normal mixture, and the ECU is trying to compensate by weakening the mixture. The readings are reasonably identical for both banks of cylinders, so the fault would probably lie with a component common to both cylinder banks.

The MAF sensor may be at fault, and it may be that the pins are not contacting the connector properly-this has been known to cause rich mixture problems as the electrical signal from the MAF becomes intermittent. The cure was to actually bend the connector pins slightly so they made a more positive electrical contact.

On a more basic mechanical level-are the secondary tensioners alright & is the cam timing correct? If the cam timing is out by 1 tooth, this can cause running problems as the combustion will be affected by late or early valve timing.

The ECU gets it's information on the exhaust gas quality from the upstream O2 sensors-these also play the major part in the feedback loop which controls the fuelling. If one of the O2 sensors has failed, then the ECU cannot properly 'fine tune' the mixture strength & may have defaulted to it's 'basic' fuelling maps.

As stated elsewhere in this thread, the S/C engine does indeed have a static rev-limiter which is set at 3000rpm when the car is stationary...

 

I just found the vacuum hose going from the left camshaft cover to the throttle body and purge valve, having some holes as it was rubbing on the windscreen wiper unit. A vacuum leak for sure can cause some engine malfunctions, just seen the example of dipstick pulling for the fuel maps alterations.
Any standard/correct data for the idle or 1500 rpm? Also some idle speed, air consumption or O2 sensors?