Lately, my Jag has not been behaving properly when moving off from a stationary start. It seems to lack acceleration, and occasionally has been revving higher and higher without changing gears or even going faster. It sometimes gets up to 4,500, nearly 5,000 revs before it changes from 2nd to 3rd, which seems high to me. It also shudders slightly while doing this. I could understand it if it was rocketing off while doing it, but the acceleration is just not there either.

Strangely, it only seems to do it when I'm leaving the house in the morning. When I leave from work in the evening, it doesn't do this. I think it might have something to do with the fact that I live very near a busy road, so almost as soon as I get past the front gate, I try to move off quite quickly to merge with the traffic, and that's when the issue starts. When I leave work, I have to go through a few side streets before I get to the highway, so the car has more time to casually work its way through some gear changes before anything much is expected of it. Of course, that could be complete codswallop, but that's how it appears to me. Also, it only started after I'd started the car and was unable to drive because the parkbrake wouldn't disengage, which was as a result of a failing battery. I disengaged and reengaged the battery and the problem rectified itself, but the gear issue appeared the next morning. The battery has since been replaced, but the issue remains. Not sure if they're related in any way.

Does any of that make sense? Any ideas as to what the issue might be? I've been told that the adaptive transmission might need resetting - not sure I even know what that means.

 

Adaptive is tech speak for "it learns". It doesn't lose its learning when the battery is off so I don't think it's relevant.

You didn't jump start the car or the like?

Otherwise, I'm puzzled.

 

No, it never needed jump-starting. The battery was failing and the Jaguar dealership told me that it needed replacing at its service about 6 weeks before, but at the price they were quoting me for a new battery, I told them I'd do it myself. The guys that eventually did it replaced it while the engine was running, which I thought was quite clever, but the issue had already made its appearance by then.

I'm just wondering if with the adaptive transmission I taught it something that I shouldn't have, hence the possible need for a memory wipe?

 

Hey Bliksem,

I have a similar issue with my vehicle that I've been struggling to diagnose:

In the morning I get a shudder / hesitation when accelerating normally.
It's never there in the afternoon, or beyond 10 minutes into the drive.

I'm looking into purchasing a diagnostic tester this weekend hoping to find some more information.
From what I can gather, it could be the following:

- Low transmission fluid. Once the fluid heats and expands the shifts come normally. This explains why it only happens after the car has been sitting for 10 - 12 hours or more. Currently my number one suspect.

- Bad coil. Coils might be going and causing misfires, but might only happen under specific sets of circumstances (for the time being). Do you get the same phenomenon when the engine is under increased load (trying to accelerate while going up hill at lower gears / rpms). I don't think this is likely as it would be a consistent issue, rather than a once a day thing.

- Vacuum hose / O-ring leak. Common problem, known to cause "hesitation". The issue with this is most people seem to find it under 'hard' acceleration when already at highway speeds, and it is a constant issue rather than just first thing in the morning. I considered that the seals might be leaking but expanding / sealing properly as the engine heat hits them, but that seems unlikely. The hesitation seems to 'feel' like it's coming from the rear of the car as well, rather than the engine (if that makes any sense).

- Differential failing / low diff. fluid. This one I don't think is likely because the problem is once a day, but I'm wondering if it could be the same type of scenario as the transmission theory - the differential oil heats and expands after the first few minutes and the problem is alleviated. The symptoms are the same, the hesitation. I don't have the 'knock' when accelerating after a stop though, so I'm considering this one unlikely as well.


The one I hadn't considered was your thinking: The adaptive transmission. My battery was also replaced the day I purchased the car, so maybe that is the issue all along.

Any members that can point us in the right direction?

So far, my thinking was the low / old transmission fluid, and I was planning on doing it in the next couple of months, but maybe it's a case of transmission programming?


Anyway, that's what I have come up with searching for issues that mimic the symptoms I'm getting.

 

This issue (Oxford's) is likely one of the common ones for that engine and at that kind of age (coil(s) by far the most likely, air leak, etc). Please start a separate thread if you're not happy with the many existing ones. As I've posted, it cannot be the adaptive trans because it is not lost by changing the battery.

 

Bliksem - changing a battery like that is very risky. A slight slip and probably get a fire or blow something up (alternator or electronic/computer module). I really hope that is not what is now the problem as it will be very painful if so.

What I would do next is buy an OBD tool which can show "live data" (they're very cheap) then:
1. check for codes (and check for P1111, else P1000)
2. when warmed up check LTFTs (long term fuel trims) at idle and at 2500 rpm (in P or N)
post what you find so people can try to help.

 

This morning I purposefully left the house very gently, light acceleration only to the first traffic light, and then drove a little more vigorously after that. It drove perfectly. Smooth, swift gear changes, splendid. I'll keep doing that for the rest of the week and see where it gets me.

Oxford, I also thought it might be the transmission fluid. I'm often at work for 10-11 hours, so the engine has another chance to cool all the way down, but in over 40 degrees Celcius (over 104 in your 'Fahrenheit' system), can it ever really cool down? Only at night I think, hence the problems in the morning. Again, just another theory that I have, so I'll be interested in hearing how you get on.

JagV8, thank you for taking an interest in this. Please excuse me for not being particularly mechanical, but what is an OBD tool, where could I get one and how would I use it? I'm more than willing to seek one out, I just need an idea of where to look. I was also alarmed at the way the guy changed my battery and warned him many times about the possible hazards and his substantial liability should anything happen, but he waved me off and carried on. I got the feeling he'd done this many times before. There were no problems, and anyway, my issue had started before he changed the battery. If anything, it got slightly after the battery was changed.

 

Bliksem,

I do have a bit of a mini-update:

Yesterday was the first day of cooler fall weather here, and the temperature never hit above 10 degrees C.

It was also the first day that I had the hesitation (though more slight, and only once) pulling out of the work parking lot in the afternoon.

It definitely would seem to be temperature related, and this time I definitely felt & heard the 'whirr' / subtle grinding noise from under neath and behind the drivers area, suggesting the transmission.

I'm nearly positive that it's the low fluid issue.

I recall reading that the transmission fluid does loop through the rad area (to warm the fluid on cold days and cool it when the engine and trans. is operating), so perhps both of our issues may be solved by simply allowing the vehicle some additional idle time until a top-up or fluid change can be done.

Right now I'm thinking I'll top up the existing fluid this weekend to ward off potential damage, and do a fluid replacement / sleeve replacement / pan replacement in a few weeks time when the parts finally arrive after being ordered.

If I get to it this weekend, I'll let you know how it goes, and whether it fixes the issue.

 

Bliksem - there's a good OBD thread in the General Tech forum. On your era car I'd consider an ELM327 or any of the ones people recommend.

 

I "think" I have a similar issue - however, mine is the opposite and intermitient - when I first start off in the morning - smooth 1 -2 upshift and after the car is warmed I get a slight vibration/shudder going from 1 - 2 but not really out of the norm.

I had a rebuilt trans installed 2 years ago (I have an extended warranty) and even the master trans tech had a hard time picking it up.

He pointed out the possibilities:

* low or spent trans fluid (I had my trans fluid serviced - still there sometimes but drives like a champ)

* The other things you pointed out above.

* Worn engine mount, worn drive shaft or worn bearing causing vibrations that are magnifying the up shift to be felt as a shudder. (one of my engine mounts is down - going to change them both this weekend to see if that cures the vibrations)

Just my $0.02 - hope you find the root cause of the issue.