O'Riell has a tester in the back room ( Innova 4400 ) that can test the coils in many ways and give you a pass / fail . The staff doesn't know how to use the machine so you'll probably have to do it yourself . The power switch is on the back . Adapter # is 34 off the top of my head . Not all stores have the tester so you would have to call first . All of my original coils passed

There is the old school method of adjusting a gap on a tool for the spark to jump across and in this way you can look on the tools scale and see how much voltage is generated by the coil . The scale didn't appear to match the physics of the matter because as the Chinese when copying it didn't reference an engineer but you can still use it as you compare one to another on this scale .

Wells has a specification table for this X300 coil as a Wells # C1203 ( double check complete ) and will give you the new % 100 output voltage of the coil . Only problem is that page was missing from the Wells book at the Autozones I've checked .

 

Thanks! Yeah I had noted a post in another thread where you recommended that coil tester, so I called every O'Reilly within 100ish miles of my location.... and not only did they not have one, they were really confused when I asked and tried to describe it

...really disappointing too, as that would have been a great way to check if one had any bad, or maybe even good spare coils.


Of course, for my specific issue, cross your fingers that it is the infamous crank position sensor. I'll know in an hour or three.

You know, a little more than a decade ago I didn't know what a crank position sensor was, but then just about every vehicle I've had since the early 2000s has had a mystery failure that turned out to be the crank position sensor. It seems to be a critical weak link that perhaps should be designed a bit better.

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There was talk of removing them from the stores as a employee liability

Someone recently found some metallic debris on the face of the CKPS clouding over the signal

Community coil swapping program ?

 

Well, the crankshaft position sensor was not it.

It turns out that I had the original crankshaft position sensor on the car though, dated 4/96 so I guess I owe it an apology as it has held up fine for 22 years. But hey, now I've got a new one that should last another 20 years

But the car still dies at idle when hot. This time it just didn't want to start after having been driven about 20 minutes, then sitting for a couple hours, then another 5 mile drive, then sitting in the Autozone parking lot for about 10 minutes and heat soaking. It took three tries to start it, and the throttle had to be feathered on the third try to keep it running. As before, once restarted it idled fine.

So, I'm pretty convinced this is a heat induced intermittent failure at this point as I've said before.

So far I've replaced:

- alternator
- battery
- plugs
- fuel injectors
- fuel pumps
- fuel pump relays
- ECU coolant temperature sender
- crankshaft position sensor

I also have three new relays for the ECU, fuel injectors and ignition coils. I need to install those and test.

If the new relays aren't helpful, the cheap "test" coils are next I guess.

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Heat soak can also effect marginal electrical connections that I'll cover when I get back in an hour .

Heat soak also opens up the windings on marginal coils .

By the time you're done you will have completed the Tour de Jaguar as well as me learning alot .

 

Well, turns out that I misread the relay diagram. The separate fuel injector and ignition coil relays shown were for the XJ12, but I did replace the "ECM controlled relay" which I assume is for the ECU.

I'll use my two spare new weatherproof relays for the starter and secondary air injection locations I guess.

But replacing the "ECM controlled relay" didn't make any difference.


This is very predictable & reproducible now though. Drive the car for 15-20 minutes to get good and hot, then park for 10-15 minutes. Then the car will not start with just a turn of the key. The starter will turn over just fine, and the engine will fire, but the RPM will then fall and die. To get it to run I have to then feather the throttle to keep it up over 2k, then it will run fine.

So, coils are next.

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Thanks, what is interesting is that this was a sudden onset failure where this stalling just started one day, had never presented itself before, and I hadn't done any recent work recently prior.

So I'm really suspecting a component(sensor, coil, etc) versus electrical connector, but you never know I guess

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Have you checked your fuel pressure regulator? When you changed your plugs did the coils have any cracks or obvious defects in them. Was there any obvious arcing from the coils to the cam cover?

I have read that if you take off the plastic coil cover that in the dark you can observe defective coils shorting out as they produce a light show.

 

The ECU controlled relay doesn't provide power to the ECU but after the ECU is powered up by " First Power " the ECU provides a ground to command the ECU controlled relay to provide power to certain regulation valves and sensors that don't use the 5.0 volt reference the ECU provides .

The " First Power " comes from fuse X and through the Papa Indy 1 or 61 connector off the top of my head without looking .

I'll go through the tricks or bypasses for your issue in the morning to keep everything powered .

As the coils heat up and ground on the side of the spark wells they can induce bed electricity into either the power wires or the intelligence return wires to the ECU causing problems that can't be followed using traditional fault / resolution methods . So that in my opinion would be the first thing to swap since you have them .

 

Al,

Sounds very similar to the issue I had. By chance did you ever mess with the two upstream O2 sensors? The reason I ask is because I had the same issue when I removed mine and plugged them in to the wrong harness. Once I switched them I no longer had that issue. Give it a try as this process is fairly simple and should take 5 mins.
The reason I mention this is because it only happens when the car is warm or in "loop" when the O2 should be in working order.

Another possible issue, throttle plate sensor? I had removed mine before and cleaned it out but did not know it needed it to be calibrated after removal.

I currently have the QYL from ebay and have had them as well for 10 months or so with no issue. I regularly check the rubber boots and still in fantastic shape.

Let me know what you think.

 

Al ,

So your Jaguar has a spot of stumble under the bonnet . It bri - ish you know . In your quest to become one with the Vrom......Vrom,Vrom ..............Vroooooooooooom .

We'll break this down into areas of concern like fuel injectors , spark , TPS adjustment ,and fuel pump and you can focus on these one at a time without giving you a target to do like checking to ensure you don't have the O2 sensor connectors crossed . This check has a valid point but in order to cover the each area fully we'll focus on one . You mentioned in you observations that the issue was a sudden onset which may be caused by your disassembly .




Spark : From the fuse # 12 / 10 amp in the RH engine fuse box there is a connector directly under and on the box itself . White / Pink wire in position # 4 of the Papa Indy 1 connector needs to be looked at . The king relay in the corner of the fuse box can be swapped with the horn relay in the corner of the LH engine fuse box in case that relay has contact issues with heat . To bypass all this bring power into the White / Pink wire after the Papa Indy 1 connector from the B + terminal post on the fuse box . Inspect the splices in the wire harness as it goes towards the coils . Inspect the ECU Black connector coil grounds in the pic below . Ensure all your grounds concerning the ECU itself are clean including the case ground as the lower rear mounting bolt .

This fuse is also the " First Power " to the ECU at the Red connector pin 33



Fuel injectors : They get there power from the Red 17 pin of the ECU and the ECU controlled relay through the Brown / Yellow wire in the Papa Indy 1 connector position 3 from fuse # 11 / 20 amp RH engine fuse box . The control wire of this relay is powered by the Brown / Orange wire from fuse # 6 / 5 amp RH engine fuse box though the Papa Indy 1 connector pin 6 where the ECU gives this control by providing a ground on Black 18 . This fuse # 3 and # 6 is hot at all times so no king relay . Same check on the connector under and on the fuse box . This same power source wire is also tapped into the EGR valve ( not on the SC engine ) , EVAP valve , and MAF sensor

TPS adjustment : It should read 0.60 + or Minus 0.02 volts dc at the closed stop on the Green / Yellow wire with just the key in the on position only before start . You can read this wire as it goes over the top of the fuel rail . Make sure the connector is locked on under there . Vee suggested you can slightly twist the blades / pins on the connector for better contact .

Fuel pump :


Editing

 

Yes, brand new (1 year old) Bosch fuel pressure regulator.

I didn't notice any coil issues when I changed the plugs a few months back, but I've ordered the cheap package of 6 coils to test, and I'll replace the plugs again since they are $2 a piece.

I've had my coil cover off for a while, but I haven't noticed any arcing with the nighttime test yet.

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Thanks, no I haven't messed with the O2 sensors at all.

I cleaned the TB last year, but was careful about the TPS. I don't think this is a TPS issue since it is heat related and the TPS is in a relatively cool location, and the RPM range is fine and not "notchy" in any part of its range or at idle other than this dying issue.


Thanks for the tip on the QYL coils. I should have them Tuesday afternoon to test if this is a coil issue.

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I changed out all six coils using the inexpensive QYL coils, and things do seem "better", but all is still not quite well.

I'm not willing to call victory, but following the replacement of the coils, so far I am unable to get the car to stall at low RPM, such as coming to a stop. The RPM seems much more stable. We drove the car around town quite a bit tonight as a test, stopping at a few locations, and so far it has been OK. But it also is quite cool tonight, so I won't have much confidence until I can drive the car in the heat multiple times on longer drives without issue.


However, I'm still having the start, stumble and die issue a few times. Before I changed the coils I could reproduce the "die" part of the experience very reliably. All I had to do was get the engine heat soaked, wait 10-15 minutes, and like clockwork I could try to start the engine, it would start, run up to RPM and then drop like a rock, stumble and die unless I feathered the throttle.

Well now I've tested this same scenario multiple times and have only been able to get it to die once, but it almost always stumbles... and drops below 1k RPM.

I've tried to catch it dying on video, but of course it won't do it when I have my phone ready. But I have caught it stumbling on startup. Here are two videos showing what I'm talking about:




The second video's stumble is so strong that you can actually hear the "death rattle" of the engine almost dying.

In both of these videos I did not touch the throttle. If it had dropped further or died, I could have given it some throttle and it would have recovered and then idled rock solid and smooth.

I've not had this issue with the engine cold that I can recall.

Over the last four years I've owned it, the car has always very occasionally done this when starting, but it became more of a regular occurrence last fall around the time these larger issues with the alternator then the low RPM stalling started. Maybe related, or maybe not and I just had multiple issues arise. But I suspect the starting and stumbling is something that I've had as a minor issue for a long time, but has deteriorated further in the last few months.

Any thoughts on what is causing the hot start stumble?

Any chance this is related to the camshaft position sensor since it only exhibits this issue upon initial startup, and if I give it gas I can power through it and then it runs fine? As I understand the camshaft position sensor's function on the X300, it only is significant upon initial startup, then the crankshaft position sensor takes over which as you know I've just replaced.

I'll at least visually check the camshaft position sensor setting since it is so easy to do:

https://www.jaguarforums.com/forum/x...or-aj16-73874/


https://forums.jag-lovers.com/t/x300...ensor/241139/5



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It's an interesting question about the Cam sensor, one that I've wondered about before.

You're right that the Cam sensor is only used on start up. It is also true that the absence on a Cam Sensor signal forces the ECU to use the Crack Sensor for positioning and the car will start with a long crank. I've tested this on my own car and proven it to be the case.

But what if the Cam signal is present but a poor quality signal, or intermittent, or out of timing? I don't know.

So a valid test would be to unplug the Cam sensor and start the car. Remember a long crank is required so hold your nerve. If it starts without a stumble you may be on to something.

 

Agreed, I'll put disconnecting the camshaft position sensor on my troubleshooting list.

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Al, it could be the ECU, something similar to what I experienced a while ago. Thought it was the fuel system, temperature sensors.....but it only misbehaved when the engine was hot. Once replaced, the problem disappeared.

 

Interesting, I'll keep that in mind.

The trick would be to find a used one that is the right part number and known good. Apparently there are several part numbers, which the parts listing makes it sound like one needs diagnostic tools to identify properly?

https://www.jaguarclassicparts.com/u...e-supercharged

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You may have overcleaned some of the connectors in your long tinkerins and you my respray them if there dry . Free

 

Yeh, there are so many different ECUs on eBay. Maybe the model number on your own ECU would be a good way to match? Anyway, ECUs are probably only different in terms of (a) 3.0 or 4.0 engine (b) NA or Supercharged, (c) Manual or automatic, and (d) Emission region. I guess if you go to pull one from the breakyard that match your engine size and whether XJR, you do not need to worry about emission as all X300 in the US would have the same emission specs. One good thing about X300's ECU is that it is programmable. I got mine from Andy who remaps the ECU to match the auto-to-manual conversion and also take care of the timing advance so I do not need the Andy's bracket. So I think the model number on my ECU has no meaning as it has been remapped by Andy anyway.