Just started happening......when I am at traffic lights or low speed/revs with air con on the engine stalls. The only way it will start AND keep running is to turn off the air con. If I turn air con off the car runs perfectly under all conditions. Can anyone offer a solution please?

 

Hello, check your alternator output.

There are several reasons for this , but it would all be complete speculation because---

The forum members have no idea what year Jaguar you have or what model and any modification you may have done.
Because you have not taken the time to give the forum members any information by creating your signature (that is where all this info should go) it is very difficult for members in the know will be able to help you, as each model has differences that need to be known before repairs or suggestion can be given properly.
Please take time to create a signature, it does not have to have any pictures unless you want, but should include Model, year, any modifications at minimum the more info the better to be able to help. Where the car is garaged can be quite helpful as well. (Climate) Thanks and

Happy Motoring...

 

Silly me, I'll do that next. For information it is a 1999 XK8 left hand drive with no modifications done to it.

 

See this thread on how to read climate system faults: https://www.jaguarforums.com/forum/x...l-codes-33067/

Then get your OBDII engine fault codes read (buy a reader or have a shop read them; some parts stores may also read them for free).

This should arm you with much more information to solve the problem.

In both cases, record the codes first, then reset the codes, and see which ones return.

 

Update.....Had alternator and batery tested this morning and both apparently are good.

 

Perhaps the air conditioning compressor is starting to sieze up?????

 

Hello Phil, because your XK8 is on the older side, you should check what your level of power is, while the car is running. The Alternator and/or battery itself could be fine, but you could have wire corrosion through out the vehicle which would mean as you add load onto the electrical system to voltage would go down.

For instance the car is running fine and then you turn on A/C unit and the voltage goes down and then say you turn your lights on it goes down even further and if it gets low enough you start having problems with the car.
Maybe some P codes, maybe the computer starts saying strange messages or even the car starts to stall.

Check the voltage at the cigar lighter inside the cabin.

Sometimes you can see the corrosion and sometimes not , you could also have corrosion on the grounding wires so you need to check the voltage that is at your battery while car running as well, even check the voltage at the main connector behind the spare tire there is a high voltage fuse back there (you need to be careful though it is high voltage back there , I think it is 300 amps gold fuse) also check the wire for heat, when you have corrosion the resistance goes up and the voltage goes down you also get heat build in the wires and especially the connections.

I am not a car mechanic or electrical guy, I just know all this because to has happened to me and it took 4 pro's almost 30 hours to diagnose and correct this problem. They kept thinking it was the alternator and kept rebuilding it!
There are many, many connections that could affect the voltage in the car and can be difficult to track down. including many grounding connections to and since the car runs on a negative system it quite important the grounds are clean and connected to clean body ground connections.

But the cigar lighter is a good place to start.

This is just one possibility and I pass it on to you from my experiences. I hope this helps you get to the bottom of your problems.
Also the lower voltage reading always came up when the car came to a stop light (low RPM'S)and the alternator was not putting out the voltage as it does with higher rpm's. also when the car gets hot the high side of radiator fans kick in and that takes a lot of juice away from the electrical system. So with a heavy load lights, A/C ,Fans, stereo any other elect. Draw and if you have any corrosion you will get high resistance which equals low voltage and car or computer problems.
In the UK there is a lot of rain, water can cause corrosion.
See the correlation?
Good luck and

Happy Motoring...

 

Many thanks for all that solid gold advice. I will certainly check those ideas out tomorrow morning and report back.
Incidentally the car is in Florida not UK but lets be honest we have a ton of rain here also so the same rules apply!

 

Thanks for all the replies, it turns out that Batroute was spot on with diagnosis. The compressor has siezed up although it it is not totally siezed as if the air con is started at above 20mph it runs for as long as you like. If started below this it can't cope and stalls the engine.
Garage have quoted me $1500 for parts and labour, does that seem realistic? Also is it worth getting a used one at cheaper price? Or am I potentially wasting money with something that might not last long.
Any thoughts would be most welcome guys.

 

If I read correctly you are in Florida so for once being this side of the pond should make parts cheaper - try Advance Auto or Autozone - or google air conditioning pump/compressor - I think there is a specialist supplier somewhere near Tampa(note I said "think" ) :0)
Because the market for a/c is so huge here it should be possible to source a replacement from other than Jaguar - make sure whoever fits it changes the receiver drier and checks for contamination before fitting the new part. Let us know how you get on - any part numbers/ cross references will be useful for other forum members.

 

$1500 is a fair price for the job. I had the compressor in my Audi A6 seize and it cost a little more than that.

 

Phil, Advance Auto Parts sells a Nippon-Denso compressor w/clutch for a tad over $325 and they also have new receiver/dryers all for the '99 XK8. It really isn't that difficult to do yourself with a little ability and some skinned knuckles. To me $1000-1500 sounds way to high as it shouldn't require more then about 2-3 hrs. for an experienced tech so even at $100 an hour plus parts it shouldn't run more then about $700 out the door.

Not being familiar with the electrical system and the idle circuits on that car what follows is just an observation based on 30+ in the car business. Most cars have something built into the idle circuit so that when an extra load is placed on the engine at idle, such as an air compressor cutting in and out, then idle speed will be automatically kicked up to handle the extra load on the engine. While the 4.0 is a relatively powerful engine when on the cam it is probably producing well under 20hp at idle and needs help when a large external drag kicks in. I's check and see if the car has such a circuit and if so is it functioning properly. If it isn't then that may be the real root of your problem as opposed to a much higher priced compressor. In addition it's also quite possible that your compressor is low of Freon which would cause the compressor to turn on and off (cycle) rather rapidly, on the order of once every 10-15 seconds. That would give you idle problems as well and would be a sign of a potential leak somewhere in the system that if NOT sealed/repaired will eventually lead to total compressor failure.

When an A/C compressor does fail it is usually the front mounted clutch that locks up first and that is usually preceded by a very noisy bearing set that will rattle like crazy. I'm not saying your mech. is totally wrong but there are other much less expensive problems that could be plaguing your car that deserve to be addressed first as I've never seen a person diagnose a compressor lock-up before it happens without one of the preceding things having occurred first.

Of course I could also be well off base here as I'm really unfamiliar with the Jag set-up in any depth.

 

More and more curious, If I switch the air con on at anything above say 15-20 mph it runs sweetly and does not cut out. If I start the car, leave it on idle and then turn on the air con before moving off, the engine cuts out. Any further ideas? The unit is not seized obviously, A local mechanic says that it is partially siezed and that the Jaguar engine is more powerful than the air con unit so it obviously forces it to start! Possible?

 

At idle the engine is generating very little power and will be easy to stall, ie a sticky air con compressor could easily stall it.

A few years ago a managed to lock my car keys in the ignition with the engine running and was able to stall it with my foot against one of the lower pulleys from beneath the car.

 

Phil,

On GM cars the air con compressor clutch is a separate unit from the compressor and can be separately replaced. Jag used to use GM compressors, back in the day, and parts were commonly available. A special tool was required to separate the clutch from the compressor.

How the foregoing relates to your Jag and Denso brand components I can't say but it may be just the AC clutch is locking up. Worth checking out says I. Ask a local AC specialist. It may not be a job for you but it ain't rocket science either.

 

Phil, a partially seized compressor is like a woman whose a little bit preggers...there ain't no such thing. It's either seized or it isn't !

Your description has all the indications of a bad idle circuit, or whatever it's called these days. Try a little experiment if you will. Start the engine and let it steady up at a consistent idle. Give it just enough gas to get the idle up about 4-500 rpm BEFORE you switch on the A/C and tell us what happens. Don't let off the throttle when you start the A/C but I'm betting you'll see the idle drop anyway but hopefully it won't stall this time. If what I think is going to happen does indeed happen you'll be a whole lot closer to the correct fix.

Two other questions. First, does the A/C comp. cycle on and off fairly rapidly? Like every 10-15 seconds? Second question. Are you hearing any rattling or otherwise loose sounding noises coming from the compressor when it is operating. You might need an extra hand with this one so you can be near the compressor area when it cycles.

 

RDMinor.........Sorry for delay in replying, just had a flood in house, not been a good week!
Started car, left on tickover for a couple of minutes with AC off.
Tickover is about 750rpm.
Brought rpm up to about 1300-1400rpm (hard to keep it exactly at this) and switched on AC.
Several times there was a "click" from engine bay and rpm would drop instantly to about 500rpm for a couple of seconds (although one time it did completely stall the engine). Had the engine beeen at normal tickover I suspect the engine would have stalled every time.
Does this help?

 

Also, to answer your other question I do not hear any rattling sounds from the area of the AC compressor.

 

I am voting for the AC idle circuit being the problem. Most cars ECU have a way to add air to the idle mix when the AC clutch is activated to raise the idle speed and compensate for the additional engine drag.

 

phil the brit...have you seen any amber or red lights as a warning of problems? Have you had anyone pull codes? I haven't been able to nail down what the English would label as an idle circuit connected to the A/C circuits but I'm convinced that that's the core of your problem.

There has to be a connection between the ignition switch position (in this case the run side), the idle speed / speed sensor, and at a minimum the load sensor or throttle position sensor. By load sensor I speaking of load on engine not load in car. When you are slowing down with the A/C on the ECM is somehow getting an incorrect signal and is, with the A/C on, not allowing the engine to maintain sufficient RPMs' to compensate for the extra drag. I believe that the English would refer to this off-throttle condition as 'overrun' and there are some mentions of that relative to the ECM and throttle position sensor. In this case that's similar to US systems only ours were generally cruder because we only go to the extremes on up-market cars and not your average Fiesta<G>

Go to page 2406 of US004 Power train manual at the following download link low on the list that you'll find.

http://www.mediafire.com/?x11yhijup29yt#8viyccmusy9t1

Without any rattling coming from the A/C compressor when the clutch is freewheeling (not engaged) then it's a pretty good bet that the clutch is O.K. and a seizing compressor piston seems unlikely. You didn't mention if the A/C compressor was cycling rapidly or not, but a rapid sequence (10-15 sec.) would indicate a low pressure/Freon condition that will lead to a seized piston if the system doesn't do an auto shut off first