Well, this just started after the car sat for about a week and temperatures started to be consistently in the 20-40F range.

Car starts fine, idles smoothly at about 700-800, pulls away and accelerates as expected. But occasionally now has started dying when decelerating and stopping. Once at a stop and at idle, RPM drops under 500, then a very slight misfire vibration... and dead. Put in park and it starts right up. One time it died right after restart, but then starting again and idled fine. Over two days driving, it's done it three times.

I've never had this happen before over the last 3 years and 50k miles, although it has always had the very occasional and mild stumble at idle.

So I'm attributing this new development to the cold, but that is of course premature.

No work was done in the week prior.

Coils are original, but seem fine so far, but maybe? Plugs are a year old. TB cleaned a year ago.

I haven't checked the battery voltage yet, and the battery predates my ownership, so that's always a possibility and batteries tend to reveal weaknesses during the cold. So that's on the list.

I did see the two OBD codes that the scan tool can't decode, B30F4 & P13B0, both of which are asked about in several old threads in this forum with no clear answers, and they seem to come in pairs. So if anyone has figured out what these codes may truly indicate, that would be helpful.

Any thought on what the codes may mean, or what other cold induced problem could cause this behavior?

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Here is a thread that may be helpful . Injector cleaning or water in the fuel ?

https://www.jaguarforums.com/forum/x...-codes-142881/

http://www.iatn.net/techhelp/49/2004...-stall-misfire

 

I read a few discussions on various forums and these codes are indeed mysterious, but the good thing is they are pending codes, not permanent? The possibilities quoted elsewhere include fault with the secondary air pump, variable cam timing (determined jointly by crankshaft position sensor and cam position sensor), MAF, water in the tank, possible leaking gasket and plug well full of oil......

Let us recap the symptoms being
(a) stalling upon deceleration and stopping
(b) occasional misfire
(c) unsteady idle
(d) dying upon re-start

To cause all four to happen would likely be fuel related, like water in fuel, contaminated fuel, or a dying fuel pump relay and/or the fuel pump or a badly clogged fuel filter, or a faulty fuel pressure regulator.

If you suspect this is a temperature related fault, a possible culprit would be the intake air temperature sensor, but such should have been reflected in the codes?

Incidentally I am identifying the causes of my stalling as well, but the symptoms are different, which I would try to share in a different thread.

 

Low fuel tank allowing tank condensation with the flux in Temps. ? This may relate to open EVAP valves .

 

Turns out, looks like it's the alternator, not keeping up.

 

Voltage regulator part number IN435

https://store.alternatorparts.com/in...regulator.aspx

the screw holding the 2 Reg. to brushes together may be fused stuck , mine was

https://store.alternatorparts.com/pa...ternators.aspx

verify that the rectifier is good by having the auto part store spin it up before ordering

https://www.walmart.com/ip/NEW-ALTER...=sem#read-more

 

Interesting; did the voltage meter on the dash show any abnormal sign before this happened?

 

Yes, the voltage gauge was indicating under-charging when at low RPM, I just hadn't noticed prior to this issue. I don't know if it was gradual, or sudden, but all was fine last week.

The stalling and under-charging became worse over a the last couple days, and I could minimize it by shutting off the AC/Heater blower and radio.

Autozone tested the battery and alternator, indicated good battery but failing voltage regulator.

Good news, Autozone has some purchasing anomaly where I can buy a brand new Nippondenso alternator with lifetime warrantee for $200 (will get core charge back too), and the re-manufactured unit was more expensive. Seems like a good deal, so it's on the way. I'll change the belts and paint the pulley/damper with a stripe to detect any future damper failure while I'm in there.

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Yeh, an affordable, new alternator would be nice for our cars at this age.

 

Sounds like my alternator is due for replacement as well, as just yesterday I started getting the occasional voltage drop from 15 to 11 while driving, and it almost died at a stop, fluctuating around 500 rpm instead of the usual 750. I will be sure to kill electrical use, thanks for the tip!

I wonder if it has something to do with me having to tighten up the belt to eliminate squeal recently. I will replace the belt while I'm at it.

 

Got this new alternator on its way from Rock Auto:
POWER SELECT 13524N
Along with the Contintental belt:
CONTINENTAL 4050385

http://www.rockauto.com/

Anybody using this one yet?

 

An update: This problem persists, but I can now somewhat reproduce it consistently, and think I have eliminated some things.

I had a few other related threads going about ground straps (now replaced) and alternator/battery (both replaced) because at one point I thought this may be a charging issue at low RPM or some other intermittent electrical issue. However I have now watched the car stall several times and voltage did not significantly drop, although it did drop a tiny bit of course as the RPM dropped and the car eventually stalled. But that's normal as the car is then on battery alone. I do think I did have a bad alternator as well late last year because it was not charging, but I think this may be coincidence.

What I have been able to reproduce is that the car will start, run and idle perfectly initially. So I don't think this is an IACV or TPS issue. And short drives will usually not have the problem show itself strongly. But occasionally the RPM will slightly dip and there may be a minor stumble when coming to a stop even on short drives, but it usually will not stall.

But on longer drives, usually at highway speeds for 10+ minutes, the car will begin to show the problem repeatedly and actually stall the car.

When there is no issue, the idle is rock solid around 700-800RPM in park/neutral, and drops around 100RPM when in gear at idle.

However, when the problem presents itself, the idle will drop to 300-400RPM, stumble and stall.

I don't see any CEL, transmission or other warning lights.

The scenario is when one slows to come to a stop or perhaps a turn after cruising at higher RPM (30+ MPH) and one lets off the throttle completely and braking.

I have not had the problem happen without braking, but I haven't exhaustively tested the scenario of just closing the throttle and coasting to see if it will stall. I do have a defective brake booster that only partially boosts the brakes and leaks vacuum slowly, so if that were related it would be a vacuum issue. So not sure if vacuum is a big issue with these cars like older cars with regard to this scenario?

So I'm just going to keep driving it to narrow down the symptoms further.

One curious thing is that my Dash Command OBD software says the throttle is showing something like 23% open when it should be closed, and 80% when I have the pedal to the floor. This is going from memory, I don't have it in front of me so I need to recheck. I don't know if Dash Command is just in error, or if perhaps I indeed have an issue with the TPS or ECU misunderstanding the position of the throttle or the cables are out of adjustment again. After I recheck the readings and cabling, I may have Jaguar do a throttle adaptation.


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OK, some additional symptoms I've noticed after driving the car all day yesterday and some testing this morning:

1) I can pretty reliably 50% of the time get the car to stumble if after soon starting the car I put it in reverse, then come to a quick stop. The RPM will briefly drop to around 500RPM, then bounce back up. Watching the tach, it almost looks "fluid" as if it were in tune with say fuel in a tank sloshing. That may just be my overlaying wishful thinking though.

2) Almost every time I start the car, whether sitting for a while or after one of the stalls, the car will usually start without any need for accelerator input (I just turn the key) but once started will immediately dip to 400-500RPM, barely stumble, and then recover and idle at 700-800RPM.

3) I didn't get the car to stall by coasting using no brake, but I did get it to almost stall using the emergency/hand brake. So I don't think the problem is related to braking directly, although deceleration clearly is the direct or indirect trigger.

4) I pulled the fuel pump #1 relay and cranked the car about ten times, and as expected the car did not start. I was curious if there were some sort of fail-safe where the secondary fuel pump would come on after several failed starts as I thought I had read somewhere, but that didn't happen. So I don't know if that is a fault or normal. But then once I replaced the fuel pump #1 relay (and swapped with an adjacent one) I was unable to get the car to run, although it would fire briefly, stumble and I could keep it running for a second by feathering the accelerator but it would then die every time (about 5 times). It produced a fair amount of white smoke and smelled pretty rich/unburnt. After letting the car sit for about 15 minutes, I went back out planning to jump the secondary pump as a test, but before I did that I tried to start the car and it started right up and idled fine (with the aforementioned brief immediate dip/stumble to 500RPM, then good idle). I'm not sure if this was just because it took a moment for the fuel to get fully through the loop and pressurized after all my "dry" cranks 15 minutes prior, or?

Since the X300 doesn't have any fuel pressure test port, is there anything in OBD data that I can look at that would be a proxy to indicate if I am having fuel pressure problems?

Should I consider pulling power to the primary fuel pump and try manually jumpering the secondary fuel pump and drive on that as a test for fuel pump function?

I'm used to fuel pumps failing or working, but not in-between, so can a fuel pump be failing and only providing partial pressure/flow?


BTW, I installed a new Bosch fuel pressure regulator and fuel filter last year as preventative maintenance when I cleaned the TB.

I put in a bottle of "Heet" water remover into the fuel tank this morning too.

I have rebuilt fuel injectors from last year, but haven't installed them yet.

I replace the "copper" Champion spark plugs annually, and it's time to do so again, and plan to do so this weekend.


Not sure if any of this provides any clues, but just a bit more info.

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Today I replaced the fuel injectors with a set of XJR injectors that I had rebuilt last year.

I didn't really expect that to make any difference, and it didn't.

After getting car warmed up by driving it about 10 minutes, then letting it sit for about another 10, it still exhibited the same behavior.

Initial startup had it start, catch and bump up to about 1k RPM, then drop immediately to dead. After two or three attempts I was able to get it to run by feathering the accelerator.

After getting it running, it hovered around 600 RPM in gear but had a slight stumble and tried to drop below 500 RPM and die a few times.

So I then jumpered the secondary fuel pump so it was constantly on, and pulled the primary fuel pump relay. It seemed to run a little better, and I was able to drive home without it dying, although it still would dip to around 500 RPM at stops.

I then decided to try to run both primary and secondary pumps at the same time to see if it would stabilize, and it did for about a mile or two where the RPM stayed stable around 600-700 RPM. But then I had it drop below 500 RPM and die when I was slowing to make a turn.

So that is a mixed result.

I figured that if either or both fuel pumps were weak that running both should likely fill any deficiency of either pump, but having it stall with both pumps running makes me think it may not be a fuel pump issue.

I can't put a fuel pressure gauge on it yet as my fittings didn't quite work out, but should be able to soon.

My next step is to replace the crankshaft position sensor.

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Could it be transmission related, like oil needing change or sensors or some sort that have been causing various problems?

 

Hi Al,

Sorry to drop in so late, but since your mystery is ongoing I thought I might offer a few wild guesses.

Regarding the fault codes, I thought they looked like some Ford or BMW codes, but a quick search doesn't turn up anything that seems relevant, and their format with extra letters doesn't conform to early DTCs anyway, so I think they are just the result of your Dash Command trying to make sense of hexidecimal information and failing.

One issue that has been associated with stalling when braking or slowing is low transmission fluid, although I think this has been with the ZF gearbox rather than the GM, but it would be worth checking just to rule it out.

Another thought is that if you haven't cleaned the Idle Air Control Valve (IACV) stepper motor and port in the throttle body, it would be worth doing so. They tend to get fouled up with black carbon gunk and if they can't close completely, they act like a vacuum leak, leading to rough idle and stalling.

Speaking of vacuum leaks, have you checked? One suspect might be the supercharger bypass actuator and its hose. In fact, thinking about that, a problem with the bypass valve and actuator might possibly be relevant, since it is supposed to redirect excess pressure back to the supercharger intake. See pages 104-105 of the EMS Manual at this link:

Jaguar Engine Management Systems: AJ16 AJ6 V12 801S

Cheers,

Don

 

I agree with Don that another possibility could be an air leak somewhere. Last year I was trying to hunt down engine hesitation and stalling problems of an X350 and an XFR - the factory scanners VCM/IDS/SDD were not too helpful as a bunch of DTCs has many possible causes. After many trial and error, the culprit was found to be an air leak from the air box or one of the vacuum hoses at hard-to-see places. A smoke test might save a lot of guessing.

 

Thanks for the additional ideas.

Regarding the fault codes, I haven't seen them since, so I think that was a red herring.

I've checked the transmission fluid level, and that looks good.

I did clean the IACV port extensively when I had the TB off a year ago to clean it. But I didn't actually pull the IACV off the TB or replace it. So that is suspect. I've actually got a new IACV, but am hesitant to change it given the risk of breaking the bolts and having to get heat in there to soften the thread locker with the TB still on the car since it is a MAJOR job to get the TB off again. But if enough of my other testing doesn't reveal anything else, replacing the IACV is on the list.

I'll be replacing my crankshaft position sensor this week as well with a Jaguar genuine part. I don't really think that's the problem, but it's probably good maintenance as the existing sensor is at least 4 years and 50k miles old.... or possibly much older.

The fuel pressure is still suspect. As I mentioned, I'm no longer suspecting the fuel pumps as much, but perhaps the check valve or fuel pressure regulator is acting up. I replaced the FPR last year with a genuine Bosch unit when I cleaned the TB, so I doubt it is bad. But the check valve could be suspect. Until I can monitor fuel pressure that is an unknown though and just speculation.

I've also got a new fuel tank purge valve and relieve/check valve. I don't have any "whoosh" when opening the tank filler, but those parts are 20+ years old, cheap and easy to install. So while I'm refreshing most of the fuel system, might as well eliminate another possible fault point.

I've also got two new Jaguar relays for the primary and secondary fuel pump on the way, again, might as well.

I don't know if I've got any vacuum leaks, but I don't think I do. Fortunately this car has very few vacuum connections.

The tip about the bypass valve is interesting. Not sure how I'd check that easily for proper function, although it probably wouldn't be hard to figure out, but I've not heard of that being a failure point before. When I had the TB off, that looked like a simple mechanical mechanism that wouldn't be prone to failure.

But after the crank position sensor and emissions valves, there won't be much left to replace, just fuel pumps and IACV. So that's somewhat good news as I'd hope to finally just run across the problem at that point. If after that it still is a problem, then that's going to be a real head scratcher.

I tell you though... in the last few years there have been a bunch of these "stalls while stopping, or at idle" threads popping up, and I think none so far have ended with a "fixed" post by the owner even after several pages of similar troubleshooting. So that makes me think we may have a common age related failure that the OBD isn't picking up and isn't one of these standard parts or electrical failures we all seem to try.

I bet it is a common but unknown issue we just haven't thought of (or been confirmed), and if we can find that elusive issue, it will be a huge relief to owners.

Or maybe it's the IACV or fuel pressure after all. We'll see.


I appreciate the brainstorming.


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Replaced both fuel pumps with Denso units and augmented with heavier duty check valves. Good news is that I now have new fuel pumps ..bad news is that I'm still stalling when coming to a stop after the car gets warmed up

The car starts right up, and idles rock solid. I can drive it for about 10 minutes, then eventually it will drop RPM below 1000 and die when coming to a stop. I don't think it has much to do with the act of stopping though, as I've had it stall like this when just pulling away and letting off the throttle too. When it stalls it then will take me 2 or 3 cranks and a little throttle get it started again, then it will idle again steady and will drive away.

I'll change the crankshaft position sensor next and see if maybe it is having some intermittent issue after it gets heat soaked. It is at least 4 years and 50k miles old. It may be older than that.

I'm not getting any diagnostic codes set currently so that makes it tough.


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Anyone think this could be a coil issue? BTW I haven't changed the crank position sensor yet, so that could still be it. I'll be changing the crank position sensor today.


I was reading another couple threads where someone mentioned that one of their coils was intermittently dying once the car was heated up and the car would stall.

I have a pile of used coils, but don't really have any way to test them. So it would be a crap shoot, especially if intermittent.

I'm thinking of buying a set of the $60 QYL coils off Amazon just as a test at least. One owner has been using them for about 10 months with no issues.




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