My car started to hesitate during mid to mid-high acceleration on all gears except the 1st. If I try to accelerate (without shifting gears) it feels like the traction control (traction light does not come on) kicks in 3 times a second or as if someone was playing with the throttle (2-3 times per second to limit the rate of acceleration).

The car still accelerates but when the gas is pressed between the medium (2/5) to medium-high (3/4) range it feels like as if there was a rate limiter on the acceleration. However, if i floor it and it shifts into 2nd or 3rd (gas pedal depressed mid-high to high) it pulls hard like usual (no symptoms of rate limit).

My transmission does exhibit the "lurch" issue and it had it for a long while ( the fluid has not been changed yet) but what I describe above has never happened before.

I have pulled of the battery terminal overnight (not sure if that actually resets or does anything) and in the morning the issue appeared gone on the way to work, however, on the way back from work the issue re-occurred. I should note that it was much colder (-16 C°) in the morning than in the afternoon (-3 C°).

When all this happens the following are true:
1. RPM needle does not exhibit any sudden changes
2. Flees like someone is cutting-off the throttle 2-3 times per second
3. The car accelerates but the rate of acceleration seems slow (slower than normal) and very constant no matter if pedal is pressed 1/3 or 1/2 or 3/5 ways down.
4. There aren't any messages displayed, check engine light is off.

Does the above symptom have to anything to do with some weired adaptive mode of the ZF6 transmission control module?

What can I do (at home) to force the Transmission into relearn mode?

All suggestions would be greatly appreciated.

2007 XJ8 VDP with 142000 km.

 

Are you on ice or anything slippery ? If wheel slip is detected the traction control will control the slipping wheel and can also reduce engine power. I'll have a look at my technical notes as soon as I can, but now I have to go off to pay my mechanic !

 

Hi Fraser

No this happens on dry pavement. The "slip warning light" never comes on. Perhaps to describe this behavior as if traction control was engaging was a mistake on my part. It's much more accurate to say that it appears as if acceleration rate is limited unless I floor it.

-Chris

 

In many cases of tranny oddities, a reflash of the TCM software produces results; it did for me and didn't cost much at all, but you need a main agent or an indy who can do it. Gearboxes themselves are generally very long lived.

Other question - is this symptom present when engine is both hot or cold, or just on warmup miles ?

 

Fraser thanks for taking the time to answer. I guess I will inquire with the local "main agent" to see how much/long it takes to reflash the Transmission Control Module (I have personally flashed many Megabytes worth of FLASH memory in minutes -- but i guess the "main agent" probably has his wicked ways).

The symptom is definitely present when engine is warm or at normal operating temperature and is non-observable when cold.

 

At my local main agent in Wilmslow, near Manchester, (a very good agent, BTW), I was charged about 30 minutes labour, no charge for software. Of course in the US it may be different. I have had two reflashes so far and both did the trick.

 

The problem worsened exponentially.

Screeching noise started, as soon as the gas pedal is pressed and 5 km/h is exceeded. Actually it may be better described as a noise that's in-between grinding and screeching.

Noise stops (most of the time) when i let off the gas or put it in neutral.

Noise comes back as soon as gas is applied - say I'm coasting at 40 km/h and apply the gas even in the slightest manner - the grinding-screech starts.

The noise - by the sounds of it comes from the rear (but really who knows where it comes from, there is too much road noise).

I'm lucky I made it home at 35 km/h. Now the beast is seating in the garage.

I'm planning to check the transmission fluid level tomorrow.

God damn it - I'm sure this is punishment for having sex with all the women I did not love.

 

Hmm, It could be new torque converter time. Not as expensive as a tranny, but still quite a lot. 142k kms = 89k miles. So much depends on how previous owners treated the car.

On the other hand with grinding noises from the rear, it could be traction or stability control related. If there is any false discrepancy between wheel speed readings the system might be trying to falsely control traction. It does this by a combination of (1) braking a slipping driven wheel (2) reducing engine torque to a lower level (3) selection of the traction control gearshift pattern