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old ECM in what happens. crank no start or no crank no start, saying unresponsive doesn’t help.
if somebody wants to be actually be useful go into IDS erase your keys and add the mininum required. then try to start to the car with an unrecognized key. x100 owners need not apply only 103 and 105
Thanks to everyone for all of their suggestions, I have tried everything that has come up a few that haven't. Still the same run for 2 seconds to 1100 rpm. and shut down.
Yesterday I called a Jag specialist who was recommended in Ottawa, and he kindly spent quite a while listening and asking questions. He has been a Jag specialist for many years, but he had never heard of this one. He said he would ask around the guys in the shop and get back to me if they had any ideas.
I then called a place in Toronto that specializes in Jag, Rolls and Bentley whom I have bought used parts off and visited in the past. He worked for Jag and has been dealing with them for over 40 years and he assures me that he has never had a car he couldn't fix. I have now sent her off to him as a last desperate act. Thank you, CAA, Plus membership for the 200 km. tow.
I will wait patiently now and hope they have the magic touch at Berkshire Auto. One thing I did get from both fellows is if it is the Key Transponder Module not recognizing the key the car would not even turn on let alone run for a couple of seconds.
I have made this point before but I don't think the implications have been fully absorbed.
Since the 1970s all cars have had a system to increase the voltage to the plug during starting because a cold plug needs 40% more HT volts than a hot one. Originally this was called ballasted ignition where a 6v coil was run on 12v during cranking and via a ballast resistor for running. If the ballast failed the symptoms were the same as you have.
Now a modern computerised version could have extra HT volts for the first 2 seconds before it reverts to normal. Internal switching within the ECU . Probably just a transistor went open .
The system is a constant energy system so that means limit the current to say 8A while cranking(2 sec) then limit to say 5A for normal running ....so you have your two circuits with current limiters ..the second has failed.
So I think that's where the problem lies ...in the ECU as it contains the ignition controls.
Last edited by Pistnbroke; 10-19-2022 at 10:28 AM.
WRONG
There is some lack of logic in this ..you are saying the crankcase is open to the atmosphere so all that can happen is the crankcase ventilation system can draw air ...but the throttle is almost closed so little suction in the corrugated pipe . Tried mine and it starts and runs fine with the oil filler cap off.
The crankcase is actually not vented to the atmosphere. The purpose of the crankcase breathing system is to use engine vacuum to create a slightly negative air pressure in the crankcase, which helps prevent oil from blowing past the crankshaft seals and piston rings, and routes crankcase vapors containing combustion byproducts back into the engine intake so they can be burned in combustion rather than vented to the atmosphere as occurred on older engines.
The engine will start and run with the oil filler cap removed, but it will eventually trigger various diagnostic trouble codes due to unmetered air entering the engine.
Current to the ignition modules/coils is controlled by the ECM. You would think that if the ECM were detecting ignition failure, it would trigger at least one DTC. But maybe not. I think there's an explantion of the ignition control in this manual:
Another possible factor that occurred to me is the variable valve timing system - but I would think that if it was not responding properly that would also trigger at least one DTC.
At the very least, we would think that Flight Recorder data should be available to the dealership technician.
So what sensors are fitted to detect sump pressure ///none /
The OP says it runs 2 seconds ..mine ran far in excess or that // ????
This is a red herring
I have my fingers crossed that Berkshire Auto can resolve this issue or at least put a finger on the problem. My gut feeling is they'll find the new ECM is at fault, narrowing it down to corrupt instructions if they dig deep enough.
I want to thank everyone who has jumped into this thread with suggestions.
I will give the current update.
After retrieving the car from the JLR dealership where they told me everything that was not the problem, fuel pump, injectors, throttle body, ignition etc. I sent the car via float to Berkshire Automotive in Toronto. A repair shop that specializes in Jaguar, Rolls, Bentley etc. with many years of experience so I am told.
The car got there and the first thing they did was ask me for $2000.00 to get started on it so they knew they would be paid. I-E transferred the money and they called and told me again all of the things it wasn't, fuel pump, injectors, and so on. So, I basically paid 2 garages at $145.00 an hour to tell me what it wasn't even though I had already confirmed all of these things myself. After about 12 weeks they called and said they had spent the $2000.00 in time with no solution and if I wanted them to keep going, I should send more money. At that point I have $7000.00 in this problem so I said I could not continue to pour money into it, so I had her floated home, another $800.00. That was about 3 months ago and at the same time I got a call to go back to a place I had worked before as an automotive engineer for a 3-month contract, so I have not had time to get into the problem myself and she sits outside under cover on the battery tender until I can have time to resume fixing her. After everything I have read, I am convinced it is a computer problem having something to do with some override for theft protection or something like that. Stil the same starts, sounds great, runs to 1100 RPM in about 2 seconds and shuts off. No stumbling like a fuel shortage or intake air problem. Just shuts down like I turned off the key. I never thought I could get so attached to a car but after 8 years of working on her because I enjoy that and driving her because I enjoy that even more it makes me very sad to look at her everyday under wraps. I will be done with this job in a few months and then hopefully she is back on the road for summer.
How depressing! Are you game for one more "Hail Mary" that won't cost anything?
Fuel, spark & air (and a bit of compression). You've confirmed there's gas and fuel pressure as well as verified spark. We can tell it gets air since it fires up, air for 2 seconds anyway. I had to chase down an intermittent limp mode issue and shared what I learned in a post "TPS and PPS adjustment via OBD." The computer has to start the engine blind, spraying gas at a preset rate to match the air it thinks is flowing in with the butterfly and Idle Air Control Valve. The combined flow should tally up to what the Mass Air Flow Sensor reads, but I have my doubts the MAF sensor is consulted at startup.
I don't know which device controls the lion's share of startup air, but at least I could visualize the butterfly in operation. I could've had my wife turn the key but elected to clip on my cell phone borescope to watch the butterfly. You can see the details..... https://www.jaguarforums.com/forum/x...ia-obd-264918/ You might have someone start the engine and watch to see if the butterfly shuts after 2 seconds. It may be worthwhile to spend some time adjusting the throttle cable and Throttle Position Sensor.
The IAC valve (Idle Air Control valve) is designed to keep a steady idle speed. The idle speed, also known simply as “idle,” is the amount of revolutions that the engine keeps when our foot is not pressing the accelerator. The IAC valve is controlled by the computer and it balances any burden upon the engine, like the usage of the air conditioner, the lights or the sound system. When the engine is cold, it helps it start by keeping the revolutions somewhat higher until the engine heats up.
Symptoms that show that your XK8‘s IAC valve is failing
The engine stalls when the car is idling (idle speed)
It is hard to start the vehicle when the engine is cold
Unstable revolutions that go up and down
The engine stalls if the air conditioner is turned on
The “check engine” light comes on
I assume the hole pictured bottom left inside the throttle body is the air source for the AICS. You would expect a Check Engine Light with tattletale error code pointing a finger at the IACS if the sensor had an electrical malfunction but maybe not for a mechanical issue. Chances are slim that the IACS is the culprit.
I thin k what is above is good but would not opening the throttle slightly with your right foot when starting over ride that problem?
If this was mine I would (refer to diagram04.2 in jag repair.com) remove the ignition coil relay centre of diagram , and jumper 3 and 5. This will ensure 12v for the coils on B and RW. See if it runs.
Then you need an oscilloscope old or a new hand held one for $50 and connect between any of G/u etc and earth. You should get a pulse when the coil fires. If this goes when the engine stops then I think you can be sure its an ECU issue.
You could then remove a coil ..fit a plug and join GU to earth ( ign on) If you get a spark when you touch it to earth it says coil system OK ECU not doing its job.
I dont think its a security issue as I dont think it would start at all.
I agree it's not a security issue, and also agree that you need a 'scope, or something that clearly shows what is happening. Can IDS do that?
My is that the spark may continue to show, but the ECM is killing the injectors, hence the abrupt stop. It really beggars belief that a supposedly 'specialist' repair shop can't at least diagnose the symptoms properly within $2000
Ignition coil and injector relays were deleted early in the 4.2 life cycle, according to the EG.
I feel for you Daro31. I also have faith you can solve the problem yourself. With willingness, a couple of free afternoons, the beverage(s) of your choice, a code reader, circuit light and a shop manual, there are few things that are unsolvable on these cars.
I'm sorry you had to spend all those bucks, but this seems like a situation that requires thought, and it might as well be your thought than that of a $145/hour technician with no skin in the game.
I’ve never heard of a garage that demands a 2,000 pre payment for repairs. Any shop should have used the results from the Jaguar dealer’s work as a starting point and then mentioned possible problems and solutions.
10-16-2022, 11:05 AM
is that the spark may continue to show, but the ECM is killing the injectors, hence the abrupt stop. It really beggars belief that a supposedly 'specialist' repair shop can't at least diagnose the symptoms properly within $2000 
