Well now I'm not certain the problem is always heat-soak related. I started the car this evening after it had sat for 24 hours, and it stumbled and died three times on the way to the store.

Maybe it is exacerbated by heat, but something is clearly still flaky when the engine isn't hot.

I thought for a moment that the ignition-on relay in the front right engine bay fuse box might have been acting up, as I was unable to get the engine to start-stumble-die after replacing it with another I had lying around. But unfortunately it acted up again.

So checking the ECU and cam-sensor, and related connections, is still on my list for this week or weekend. I'll update as I check more.

....running out of things to check or replace

.

 

While checking some of the last simple things are still on my list first, I'm mentally preparing for how to check some of the less simple things.... and I'm running out of sensors or "actuators" to test.

But two things that are still possible problems, both of which I would love to avoid dealing with if possible, are the IACV and TPS because both are difficult, risky and/or expensive to try to remove or replace.

At this point I suspect the TPS less, but the IACV is directly tied to low RPM/idle performance.

The TPS on the XJR is a real problem to access based upon my experience last year cleaning the TB, and if bad is very expensive, and would require a reorientation if replaced. So I'll probably leave anything with the TPS to a shop.

The IACV is tough to replace on any XJ6 due to the thread-locked bolts, but adds additional difficulty with the XJR due to its placement up under the intercooler. So before trying to pull it off and install a replacement, I wonder how one could test if the IACV may even be the problem?

I think I read somewhere that the IACV can be actuated with WDS/IDS, but I unfortunately don't have that. So I wonder if another approach might work...

Here's what I was wondering: Could one unplug the IACV when the car is idling normally, and when unplugged would the stepper motor/plunger remain in position and not move? And if yes, what ill effects could one expect upon driving the car with the IACV stuck open?

I'm sure that leaving the IACV plunger open would cause air mixture issues when the throttle is not closed, but if it would still run reasonably that could be a good test if the car doesn't die anymore at idle. So one would be exchanging one problem for another, but might identify if the IACV is sometimes not opening properly at idle.

What do you think? Is that a reasonable test to identify or eliminate the IACV as a potential contributor?

.

 

Al,

I don't know the answer as to whether disconnecting the IACV might be a means of testing it. My first thought is that when reconnected, the plunger might be in some position other than the one expected by the ECM. I think the ECM can readapt the IACV, but it may trigger one or more DTCs first. You might study pdf pages 88-90 in this manual to see if there are any clues:

Jaguar Engine Management Systems Self-Study Training Course 801S

As far as I can recall, failure of the IACV stepper motor is rare. But it is common for carbon to build up on the pintle/plunger/piston and in the valve bore in which it operates, preventing the pintle from fully closing and allowing unmetered air into the intake.

Cheers,

Don

 

So, this is interesting.... I was looking through some of the Jaguar DTC decodes, still not finding the codes that I originally posted in this thread, so I thought "what the heck" and Googled them.

I'm certain I had Googled for the codes before, but maybe I only searched for Jaguar associated codes?? I don't know, but here's what came back:


B30F4: Nothing found, other than lots of questions on various forums asking about these two codes together being set on a Jaguar, and what they mean.

P13B0: Camshaft position sensor? Hrmmm

https://www.autocodes.com/p13b0.html

https://www.engine-codes.com/p13b0_bmw.html

https://www.2carpros.com/questions/j...ar-vanden-plas


Anyone have an iATN login to see the full response in the following:

1997 Jaguar XJ6 4.0L Hesitation, Cuts out, Stall, Misfire - iATN



So, that's mighty curious that at least the P13B0 code seems to be tied to the camshaft position sensor function on other European cars. And we've been talking about long crank times, and if that could have any other impact while running. So the camshaft position sensor is definitely on my list to check.

.

 

OK, still no solution.

This weekend I cleaned various connectors on the right side of engine bay.

I replaced the "ignition on" relays with new in the right engine fuse box, right heel board, and auxiliary location in the trunk.

I also bought a new camshaft position sensor element, rebuilt the camshaft position sensor and timed it properly. Good news on this minor point is that the car now starts right up on one key turn... when it is not acting up.

But as per all past reports, all I have to do is run the car around town or on the highway for 10-15 minutes to get it good and hot, then it will reliably die when dropping to closed throttle when stopping. It also will be hard to start, taking a feathering of the throttle to get it to stabilize and idle.

I still need to check out the ECU connectors.

I also have unplugged my MAF when the car is running well, and as expected the car will stumble and die. When the car isn't starting, unplugging or having the MAF connected has no effect. So would you agree the MAF doesn't sound like a likely culprit?

So I'm running out of things to check.

I've attached a zipped scan log that I pulled from DashCommand. It is a CSV so can be opened in MSoft Excel. If one looks for the engine RPM where it falls below approximately 300-500RPM, you can find the places the car died when coming to a stop. There's lots of extraneous data that is irrelevant and I think DashCommand just makes up, but there is also a lot of real data too.

Maybe someone can see some parameter that looks unusual as a clue of where to look next? I'd appreciate any OBD log file gurus taking a look.

...once again, I KNOW this is going to turn out to be something simple, one component, one wire, one relay, something that just decided to go into zombie partial-death about 6 months ago. If we can just FIND it. Unreal.

Thanks.

.

 

ELM327 makers do make up stuff based on other data points and calculation assumptions to say look we can give you 600 things . Only trust actual sensor values .

If you where to take a heat gun and warm up the stepper motor in the IAC valve you may find a 1 of 4 windings open as the motor warms up . You would have to take a piece of paper and make a column 1 - 4 including up to 3 - 4 , as any of the 4 pin combinations would need to be checked . This is on the assumption that as the ECU sees rapid decrease in TPS valve to full close it would open the IAC wide open as a anti stall feature and as the RPM settles down from high to the normal 700 the valve is scheduled down more closed until the RPM reaches the idle setting . You may have a winding bad that gives you that initial wide open position in the schedule .




Reviewing your runs .

I see the data notepad but my Excel licence key is up in the F$(*#) cloud somewhere .

 

Thanks, the IACV is one of the last components that hasn't been replaced, so it is suspect.

I have a new IACV already, but the challenges of the infamous thread locked bolts have kept me from replacing it until it is a last resort. I've broken several of those bolts at the wrecking yard trying to remove an IACV from the TB.

But it's on my "potential" list, and I've got some acetone and methylene chloride ready to go to try to dissolve the thread locker.

.

 

Someone recommended putting some heat on the loctite

 

Yes, but putting heat on the bolts on the XJR is tough. I may try, but it is tricky to get in there and apply the heat.

So I'll look into softening the thread locker chemically.

 

I forgot that that you have the unfortunate luck of having a SC engine and the difference .

Vrom ........Vrom............Vrom,Vroooooom .

On the NA would involve removing the TB and applying heat on the inside of the throat to the area of the treads .

One possibility would be to warm up the engine up to the point where the fault occurs and reading the 4 wires for resistance at the ECU connector . That way you would have definitive proof that replacing or not is the direction to go .

There a 6 different pin 1 , 2 , 3 , 4 pairs to check on the black ECU connector towards the valve step motor as marked .

Your combinations to check are :

R - G =

R - P =

R - U =

G - P =

G - U =

P - U =

 

Thanks, I'll look into that when I check the ECU connections for water contamination.

I just finally called a well known local (well 40 miles away) independent mechanic that's been recommended for a few years, Dias Automotive, and described my problem.

He suspects the ECU after I told him all of my problems and what I've fixed so far. He was really great to talk to, and joked about how "unhelpful" the OBD is on these cars when you have a weird problem like this. But he's seen it before.

His son has a 96 XJR, and they've offered for me to bring the car up to the shop the Sunday after next and they'll be happy to let me swap out ECUs and put it on WDS/IDS to see what they can find. I've very excited about that opportunity and to find someone local with some of the necessary specialized diagnostic tools.

.

 

Look for on the ECU on the socket side tho 2 tabs that pinch the pins / blades . Mine had 4 of these tab pairs missing . I have a part number and source if needed . The release tool is a 2 prong device to release 2 locking tabs at once .

https://www.rennsteig.com/en/products/accessories

 

I'll cut one of the ECU connectors in half so you can see how the sockets release out and you may be able to salvage some used sockets before you were to touch your connector as practice for tech to do or yourself if you identify any on yours that are bad . The sockets can be sodiered on without the special crimping tool .

 

I couldn't find that exact tool you have illustrated above. Do you know the tool part number?


Thanks for the offer to show how the clips go in.

Now I'm on the lookout for a 96 or 97 USA (or maybe Canada too?) spec ECU for an XJR6. I think the 95 didn't have EGR, so I doubt the ECU from a 95 will work.

.

 

Andy ( XJR Engineer ) in England may be able to reprogram any of the X300 series ECU's as he has done for " Q " in Hong Kong on his 95 XJR transmission converted over to manual . The hardware in the box is the same , just the software if I"m correct .

Tool # TOL - 019 . I don't have one but plan to as I replace all of my sockets on both of my ECU connectrs . I could order them to you and then sent it to me after you are done . 36 x 2 is 72 pins should I order 144 ?

https://www.simtekuk.co.uk/product.p.../?k=:::4475179

 

So I don't know if anyone has had an opportunity to look at my logged scan data. But I've been replaying it and re-educating myself on short-term (STFT) and long-term (LTFT) fuel trims, and I'm far from an expert however I think there may be a clue there that may be at least showing something of concern.

Most of the materials I've been watching say that there are two quick "rules of thumb" to diagnose normal O2 and STFT and LTFT fuel trims. The O2 sensors should oscillate regularly between a bit over zero V and 1V, averaging about .450V. And the STFT should be as close to 0%, but typically are considered normal between +/-3%. LTFT should ideally be close to 0% also, but again a general rule is that the sum of the STFT and LTFT should not exceed +/-10%.

Looking at my logs, based on those rules above, the O2 sensors seem to be oscillating between 0-1V and therefor working fine. I think. Feel free to look at the logs and validate that deduction for me.

The bank 1 and bank 2 STFT and LTFT do have some wild spikes, but generally are running around +/- 3 to 5%.

However, bank 3 and especially bank 4 STFT are in the positive high teens and lower 20%, and the LTFT are almost solidly positive 7 to 9% which I think indicates a very lean condition where the ECU is trying to add fuel, normally because of an vacuum/intake or exhaust leak.

The car of course has four O2 sensors, so I assume DashCommand is calling bank 3 and bank 4 what are actually bank 2 sensor 1 and bank 2 sensor 2.

If I had a vacuum/intake leak I would assume I'd see these high STFT and LTFT readings across all four sensors, not just the ones on bank 3 and bank 4. So this leads me to suspect an exhaust leak.

Now I am almost certain I have cracked exhaust headers because I can sometimes hear it, although I haven't removed the heat shield to look. Up to this point I just assumed it was a noise nuisance, but now I'm wondering if it is causing me some fuel ratio issues.

Could this cause my stalling at idle? I have no idea, thoughts?

But even if this isn't causing my stalling, it certainly can't be good for performance and economy. So it looks like I'll be looking for an intake or exhaust leak this week as well, and if the exhaust headers are the cause of the fuel ratio issue, I guess I'll temporarily plug the cracks with furnace sealer/putty and see if that helps.

....just another clue.

.

 

Hi Al,

If you discover you do have cracks in your manifold(s) and can access them to apply a patch, I've had good success with a product like this:




On our '93 XJ40, a previous mechanic had stripped the EGR pipe fitting into a manifold. I glued it back in with this ThermoSteel and the patch was still going strong at 198,000 miles.

Cheers,

Don

 

'positive 7 to 9%' isn't very lean and should not affect you in any meaningful way. It wont be cracked manifold either. I think at this point, you're overthinking this and you'd do with a fresh pair of eyes looking into it, especially with this being SC car which is significantly rarer than NA cars and therefore less users are able to help(me included as not familiar at all with the SC side of things)
You can unplug the IACV no problem, just make sure that its in a parked position(which is fine for idle) and it should tell you whether it gets stuck while extended.
Your TPS readings looks ok and never drop below 12.2% which is fine and if these readings are reliable I'd leave it alone. You can clean/change it if needed, just make sure to set it up to 12.2% when closed afterwards. If this is unreliable, eg this reading drops below 12% and just doesn't get logged because the car stalls, then this could be a whole different story and it would of course cause stalling(although normally this would usually happen at other speeds too)
Stalling when getting to stop is usually caused by air leaks, poor fuel pressure or weak coils. My straight six car would stall with air leaks(eg vacuum lines disconnected from the intake), with poor fuel pressure(clogged fuel filter and faulty fuel pressure regulator) and with dying coils(which were still working but giving weak spark). I assume you have correct throttle plate gap when closed.
Checking ECU might be a good idea, open it up and see what's inside, other than that and considering your troubleshooting - a fresh pair of eyes is what you really need here

 

I have developed a patch for my crack between the # 2 and 3 cylinders from the front but have not applied it yet . It involves a bracket I made to insert straight ( not bent ) bicycle spokes to hold some stainless steal mesh / screen materiel to hold the Thermoseal product in place . I haven't executed the layup yet so I don't know if it would work in the long run .

 

I'm very late on this... sorry.

I've no idea about the first, but P13B0 is very weird. DTCs with letters in the last 4 chars didn't come in till about 2007 and I would not expect them in these cars.

Granted, being P1xxx it's allowed for the maker to do as they please, but I suggest ignoring the code entirely. Looks more like a software bug than a code! (For this era car.)

Just to emphasise, all P1 codes are non-generic. Makers can make up any meaning they like, can change them any time they like and can make them quite different by year, car model - well, anything. They could even make them unique per car (no-one does).