XK8 'noob here (1 week) so pls be gentle I've noticed that, when driving, if I release my foot from the gas pedal the motor exerts quite a noticeable drag on the forward motion. It's particularly noticeable in the morning when I first start the car. If I don't reach 2nd gear, and I release my foot from the gas there's a pronounced drag. In neutral gear it coasts as it should. Is this normal? There are no warning messages. The gear shifts are smooth. The engine is quiet. The temp gauge reads normal. Perhaps I should mention that I just had a coolant leak on the car, resulting in overheating. Cost big bucks to sort that out but I even asked the Jag dealer service manager if all damages were fixed and he replied yes. It's very annoying and certainly detracts from my enjoyment of the car. Normal or a problem? If the latter, how big? $$$?

Thanks in advance. In case it's important, the car has 72,000 miles on it.

 

If it has the ZF 6HP26 as I think it does then it's trying to heat up the trans oil I think.

 

I'm in So. FL - high 80's today. And the car had been driven for over an hour. As much as I'd like that to be the explanation, I highly doubt it.

 

Could also be a caliper that is sticking.

 

Thanks, but as I mentioned, in neutral it coasts along effortlessly.

 

Not sure and hopefully someone else can confirm but this sounds about normal. You say you have not reach 2nd and take your foot off the gas, so the car is still in first. Just like a Manuel transmission the car will engine brake. If you speed up and get thru the gears and let off the gas does it coast or drag? Also this may be a stupid question but you do have the car in drive not in a lower gear on the J gate, correct?

 

It's definitely in drive and yes, if I speed up and get thru the gears, then let up on the gas pedal the motor will put a very noticeable drag on the forward motion instead of letting the car coast along. And the drag force varies a bit - e.g. when the car hits around 30mph you can feel an extra drag on the forward motion. If I accelerate when this is happening it almost feels as if the engine is working against itself - wanting to accelerate as well as decelerate at the same time. Oddly tho the engine remains quiet and the shifts are smooth as silk.

Essentially, any car will not 'coast' as freely when it's in drive vs. neutral. The problem here is that this effect is much more pronounced and noticeable.

 

That is strange, wish I could help. Mine will just roll along while in drive, no overly noticeable "drag" or engine braking when I take my foot off the gas.

 

If you lift the rear, put the gear in drive, engine off and rotate one rear wheel? Should be smooth. Block the other and see if the diff action makes a difference. Maybe interesting to run the engine and drive train on the stand to.
Justmy thoughts

 

There's one small "been there done that" which many of us have discovered after a few days of ownership and which often catches out the unwary ..................... are you sure the handbrake (parking brake) is off. The whole set-up is counter-intuitive, and is the source of many posts on this forum.

 

Strange symptoms . . . .

Another SWAG. While costing in gear touch the brake petal enough to turn on the brake lights but not enough to feel any braking. That should release the torque converter lock up. Any change?

I had a transmission control module that would not release the lock up solenoid valve on shifts. Had to use a grafting PID reader to see it.

 

Thank you for this suggestion. If/when I bring it in for service for this problem we'll give this a try.

 

Absolutely - not my only Jag so I'm familiar with the hand brake. Also, there is no forward drag when the car is switched to Neutral.

 

humm, drive it for a bit and go around and feel the rims or the caliper for heat that you should not be feeling? Hung caliper or ebrake?

 

Everyone is mentioning this. If I place the car in neutral there is NO drag - it just coasts freely. Unless I'm nuts (a possibility), this would rule out the above.

 

You say your familiar with the hand brake, so tell me this: When you pull up on the brake does it move freely up about 4 inches or so and then becomes hard, or does it feel like it's applying as soon as you start the pull up?

As to the coasting, say your driving along a 60 MPH and then let up on the gas. Does it drag down right away or coast for a moment or so then start to drag down?

Remember this. You have a six speed transmission there and when you let up off the gas around 55 or 60 MPH, the transmission will coast for a moment then down shift to the next lower gear, on through the gears. Once it get's to the fourth gear, the drag will really start to show and if you let it, once it get's to the third and then second gear the drag should be very pronounced. Once you get the shifts vers the rpm memorized, you'll be able to know when the next shift will take place (only during coast down). In drive (D) up shifting is determined by you and your foot pressure---with-in reason that is.

 

No joy, but thanks - that would be too easy

 

My first thought was as some else mentioned; the torque converter not releasing. I would not say that with my car there was such a pronounced drag you have that I interpret from your descriptions but, I may have had a similar issue.

I bought my car with 60k miles on it. I never had any real issues (except reoccurring fuel pump failures which is totally unrelated to this subject) until I was at about 98k miles or so when I started experiencing very slight surging issues, so slight that most people likely wouldn't notice. I have a thread on this forum about that, so I won't go into great detail here, but you can read the thread if you want to by doing a search on the forum. Over time and a few thousand miles after the surging started, the problem degraded to engine failsafe mode intermittently and it became progressively worse. Codes indicated a throttle body issue, which likely was the TPS. I replaced the throttle body (which comes with a new TPS) which resolved my issues. What I did not expect was how different the car feels at slower speeds, particularly when coasting, and coasting to a stop. Initially AFTER the TB replacement I would actually think the engine was stalling when coming to a stop because when letting off the gas pedal and coasting there was a distinct disengagement between the engine and transmission and looking at the RPM's I would notice the needle would drop to around 600 RPM while coasting. This never happened before. While subtle, it was a significant change to the way the car ran prior to the TB change. In fact, even now after several thousand miles, it still catches me off guard. I also have noticed that the throttle is not as sensitive or touchy as before - Upon starting from full stops, I had always felt that the throttle seemed very difficult to smoothly pull away, as if I was in a race, even though I was trying to smoothly pull away. I am not saying the throttle was either off or on full, just very overly sensitive at starts.

I had surmised that the original TPS possibly was never properly adjusted, and it was sending incorrect signals to the ECU and TCU, causing the transmission to think I was still on the throttle and not allowing the torque converter to disengage the transmission from the engine until it was forced to based on land speed. I also notice now that I need less braking pressure when coming to a stop (makes sense).

So again, I don't know that my issue was so pronounced as yours, but maybe similar? I don't think there is any way to actually test or adjust the TPS, and $350 or so to replace the throttle body (yourself so no labor in that cost) may seem like an expensive test. Good luck.

 

When I started driving some Mercedes (300/500sl) I'd found the transmission would feel much different than my American cars. I tried to explain it to my brother in-law but it's a feel like it's more tightly coupled, of course neutral takes this away but it's not a power gear. I have the same feel in my xkr, so you're probably feeling this (not sure what ur other jag has for transmission). Do you feel this when using the j-gate gears (i didn't see u mention this). There is also some learned behavior in the shifting, since u're new to the car it has all the po settings and may take time for it to relearn your driving. I think you can reset this and go through the driving cycles, some one here can chime in or you can do a search on how this is done.

 

The hand brake doesn't get tight until around 4 inches up, and the red brake light goes on. We can rule out an engaged hand brake.

The drag doesn't seem to take effect until decelerating to around 45 MPH and it isn't constant. As I mentioned it gives a strong tug at around 30 MPH. It's also somewhat unpredictable - e.g. if I accelerate, then let up, it might coast freely. I guess I can safely say it's related to downshifting. But I've never drivein a car in which you can't simply coast down a hill. I wonder what effect it has on gas mileage.

My local Jag dealer's service advisor is going for a ride with me tomorrow. I'll keep everyone posted.

As I mentioned in my first post, the car overheated around a week ago, resulting in a huge repair bill. No one has mentioned the possibility of the trasmission fluid getting to hot, causing it to lose some of its properties - e.g. lubrication. It was a thought that occured to me.