Howdy all,

Well, my first few weeks of Jaguar ownership have been character building to say the least, suffice to say I think I have enough character now and just want the car behave itself as it's my daily drive.

First day of ownership the water pump packed up. That has since been replaced, not a drama.

Now it idles erratically when warm to full operating temperature. It starts okay, seems relatively okay when cold, then 10 minutes or so into the drive it gets temperamental, the revs are all over the place and it cuts out. Not pleasant in city traffic that's for sure.

Once hot, it seems to settle down.

The car is dual fuel, and now will not operate properly on LPG. I have put injector cleaner in the tank and have been running on petrol (98 octane unleaded) for a week or so now, hoping this would cure the problem.

I have Googled the problem, but am a bit lost as to where to start looking for a solution. A few weeks ago there were some loud bangs from under the bonnet whilst running on LPG, I have checked for damage but everything seems intact.

Is it best to take it to a specialist? Would really like to 'uncomplicate' things by ditching the LPG system, I reckon the Jaguar is fickle enough without having all this other guff getting involved.

Any help would be greatly appreciated.

Thanks.

 

@Undertaker

I read your post a few times and I'm trying to work out exactly the symptom....... it sounds like the car starts fine, and runs fine when it's really warm, but at some point during the warm up it starts idling strangely ? When it acts up, is the idle just going down and causing it to stall? or is it going up and down ?

If thats the case it would narrow down the list of areas to look (ie something to do with the cold start/warm up system)

Was the car ok when you got it ? (Did you get to experience a full warm up cycle before the water pump gave up?) So far in my few years of Jaguar ownership I had came to learn that it's quite common for a problem to occur while something else was getting fixed........ Obviously changing the water pump requires a lot of fiddling around in the engine bay....... if the car was ok before the water pump failed, then that would suggest to me something has been knocked or disconnected during that job.

As for the LPG loud bangs under the hood.... thats a bit concerning. Same question there...... was the idle ok before the loud bangs ??

A lot of my own sleuthing has resulted in me finding I did something to cause a new problem while trying to fix a different problem.

 

Thanks for your reply. The problem is getting worse, so I ran it from a cold start yesterday in the driveway to full operating temperature. Started fine, idles okay for about 5-7 minutes, then idle speed suddenly drops and it wants to stall.

Did the same thing this morning, starts fine, idling just under 1000rpm. Five minutes later idle speed drops to about 800rpm. Then a few minutes later when closer to full operating temp, idle becomes erratic. It seems to run okay when on throttle, but when you lift off as you would for traffic or stoplights, it wants to stall and starts 'hunting'. So I need to manually keep the revs up to prevent it from stalling.

As for the LPG, it feels like the handbrake is on compared to running on petrol. As far as that goes, I just want to use the gas I have and then remove it.

I've only had the car a month or so, so don't know the history of the vehicle, and trying to unravel what the previous owners have done under the engine bay is a nightmare.

So I'm not sure if this is an electrical or mechanical problem, another reason why I hate ECU's and EFI, too much stuff to even attempt to diagnose for the home mechanic!!

I'm thinking something's gone amiss with the LPG converter thingy ever since it made those loud bangs, which it hasn't done since I've been running solely on petrol.

Any ideas would be greatly appreciated, or do I do the basic system of elimination, plugs, HT leads, fuel filter, coil etc? I've checked for vacuum leaks, there appear to none.

 

Hi, if your car has fuel injection, then this series of articles might point you in the right direction.
One of the early pages talks about the problems which can occur with the air flow sensor after a spitback in the inlet manifold. I don't think that is causing your idle problems, but worth looking at.

Below is a link to the articles; they are written by Roger Bywater, who was a development engineer at Jaguar.

Fuel injection and the Jaguar XJ6 4.2 Series 3 / AJ6 Engineering


This page has details of the idle control setup

Fuel injection and the Jaguar XJ6 4.2 Series 3 / AJ6 Engineering

Last page has some good fault finding tips

Hope this helps

 

Ide be willing to bet its the idle air bypass malfunctioning. I didnt see anyone else mention it?
Its the odd shaped aluminium thing attached to the water rail that has a black hose connect into it. Inside there is a flap that controls the amount of air let past the throttle butterfly. It is governed by two means, 1 it has a by-metal strip in it that closes off airflow as the car warms up and 2, there is a small servo that the ecu uses to open the airflow up a little bit. From experiance when they play up all that is needed is a good rinse out with carb/ airflow meter cleaner followed by some inox or wd40 or whatever to keep it lubricated. removing it is an issue because the thick black hoses that run into it on the top and out of the bottom and back into the manifold almost always fall to bits as soon as you try to remove them. The one on the top can be substituted with a bit of heater hose as its not under a great deal of vacuum but the bottom one needs to be the genuine deal as the manifold vacuum will completely crush anything soft like heater hose at idle. I think you can buy the hoses new but they are fairly expensive. mine are held together with tri-bond at the moment.

Otherwise it could possibly be coolant temp sensor, tho I doubt it. might also pay to change the thermostat as the by-metal side of the air valve relies on it working correctly.
As to the gas i would seriously think about having someone look into and fix it up, you will probably redeem repair cost in the fuel savings you make in the first few months. Also, once gas is running right it is going to be far less problematic then the slew of Lucas sensors, clips and wires that run the fuel injection system. Depending on how the system is set up the only electronic device you should need is the ignition amplifier, which is reasonably reliable.....

All food for thought,

Jay

 

Hello Jay,

Thanks for the tips, I will investigate. Funnily enough my car originated from Melbourne until the owner saw sense and moved to Adelaide, (sorry, couldn't resist).

Anyway, I've discovered a service invoice from 2006 informing the owner the Airflow Meter has a bent flap as a result of backfiring on LPG. This is what happened to me a few weeks ago, 2 x severe backfires after which I have only driven on petrol.

Mechanic recommended replacement, but there's no record of this being done as the owner sold the car shortly afterwards.

So I rang the Adelaide Jag specialist today re price and availability of a new or recon AFM and was told there's none in Adelaide. There is a new one in Sydney at AU$1100-00, and a used one at AU$350-00 with no guarantee of it being serviceable. They reckon my best option is to import one from the UK.

I've since removed the AFM to see if it can be serviced or reconditioned or bench tested. What I really would like to do is convert it to carbs, I hate all this ECU and temperamental relays and sensor stuff.

Beginning to think the Jag was a bad idea, despite it being a beautiful car and a real head turner, should stick to my ZG Fairlanes!!

Cheers,

Paul.

 

I dont know whether you are allowed to recommend people but i deal with this guy a bit and he is quite reasonable compared to allot of the others with his prices.

Jaguar XJ6 Series 3 AIR Flow Meter | eBay

He has most of the stuff you would ever need through your series 3 and as I said is cheaper then most out here in oz but ide give him a call and make sure he can still get them first.

Regards Jay

 

Idle problem has now been resolved. I scored a new Bosch Series 3 AFM on Friday, installed it and changed plugs and filter. Necessity meant I had to also remove the LPG converter, as I was a tad careless and accidentally snapped one of the fittings whilst fitting the AFM. Fortunately I had isolated the tank, so no danger.

Anyway, car fired up first attempt and idles perfectly with no fuss or erratic 'hunting'. It was hot today in Adelaide, and even in city traffic, stuck at lights etc, it behaved itself. Result! Just needs a proper tune.

Onto the next problem, installation of a stakedown kit.

Cheers.

 

Well, after relieving my wallet of $560-00 for a new AFM, it seems that was not the problem as the car stalled twice today on the way home from work.

So, I have a new AFM, new plugs and air filter and disconnected all LPG stuff that could contaminate or interfere with the factory EFI system. I have checked all vacuum hoses and ignition wiring, all appears fine.

Car runs okay once at operating temperature, albeit a low idle which I'm not too comfortable with. And it is over-fuelling, but I cannot afford a professional mechanic to tune it.

This stalling happens during the warming up cycle, and I'm now worried that it will stall, flood, and then really embarrass me by not re-starting in the most inconvenient place.

As money is now ultra tight, which of the sensors should I be looking at first in an effort to fix this problem. I am going to clean up the idle air bypass thingy tomorrow, but with the car behaving this way I'm not keen driving it again until fixed.

Any ideas would be greatly appreciated.

Time to drag the old Ford out of the shed again...