alright guys,

just took a nice ride on the highway to school, and noticed the following problem.

At about 55-65 mph if i take my foot of the gas pedal the car jolts, and i put it back on and it jolts again.

It almost like a bad mount, but i really dont know....

Any suggestions...?

thanks,

Rich

 

Checking the trans mounts sounds like a good place to start.

Any other symptoms?

Cheers
DD

 

I had the same problem in my XJ40. When cruising try taking your foot off the accelerator slowly and smoothly to see if it still does it. Mine wouldnt do it if I was smooth on the accelerator.

I never had my problem fixed because I was rearended and the car was totaled before I got around to fixing it. But if I remember right it was the tranny mounts, but its been a few years so I cant remember if it was the exact problem.

 

so i checked out the trans mount and it looks good. I also checked the fluid and topped it off. Today while driving to work, at about 50mph i was cruising with my foot of the accel pedal and the car would drop down to 1600revs then back up to 2000revs. It was like the car was braking, if i put my foot back on the accel pedal it would be fine... Thanks, Rich

 

At the speeds you are mentioning it sounds like the torque convertor "lock up" is being a tad harsh in and out of lock up.

These cars lock up the convertor at somewhere around 52mnph to 60+ mph, depending on how much gas you got going on.

As said already, drive it with a nice and smooth steady acceleration, not pedal to the metal stuff, and see if anything alters.

Mine was a little harsh at first, and 2 trans oil changes later it is barely noticeable.

Having said all that, I looked at where you abide, and you did NOT get the 3.2ltr cars, only the 4ltr cars, which have an "electronic control" transmission, which is signalled from the TPS (throttle position sensor). Maybe that is going flaky and giving weird signals to the trans control unit???, dunno, my 3.2 is a good old cable controlled trans, simple as they come.

 

thanks for the input so far guys,

That seems to be the problem area 50mph+

I just got home from work, and it seemed a little better, but still not right.

I scanned the car for codes today, only old codes, which where o2 sensors, fuel air mixture, and a thottle body code...i think!

since i have had the car, i have been real gentle of the gas.

 

My suggestion would be to give the transmission a simple oil and filter change. Fresh oil will do wonders, if that "top off" has freshened things a tad, which it sounds like may have. Then do it again in a few months time, and slowly "flush" all that old oil out of the transmission.

Some "flush" the transmissions, I DO NOT, as too many failures have been reported from the "shock" of new oil, or maybe its all smoke and mirrors, dunno, I stick with my way with my cars, and never had a trans failure in 42+ years of Jaguar operation.

 

thanks grant,

you been a great help.

I will do a drain and fill on it hopefully over next few days, and let
you know.

thanks again,

Rich

 

would you reconmend me to put a conditioner/additive in it.

i was going to put a full synthetic in it?

Rich

 

I would stick with STANDARD fluid, no bottles of brew, I reckon your trans is just suffering from lack of TLC, and some fresh fluid will do wonders.

The first change will/should make things smoother, and after 2 or 3 it should be sweet. If when you drop the pan, it is CLEAN, the signs are good, so the next 2 or 3 changes can be done by draining the fluid out of the dipstick tube, undo the big nut and let it run out, and simply refilling as required. Once you are happy with it, one last time with a new filter, and then do it again in 2 years time as per normal procedures.

ZF do not recommend synthetic fluid in these "older" style transmissions, at leat down here they do not.

 

just got one more thing.

While driving to work today, after hit 50mph and my car do its "thing"

I stopped at a light, and revs where at like 1500, and then it did it again at the next light.

A few lights down and it was fine.

does this help, could this be a tps? no engine light on though...

thanks,

Rich

 

Could well be, but there are many things that control idle.

It could be the throttle cable sticking, or the return spring having a female moment, and I seem to remember a bulletin somewhere about these springs. From memory (this will be good haha) these springs were not wound tight enough, and did not return the throttle mechanism to zero some times, sounds familiar me thinks.

TPS maybe, but I reckon that would throw a code??.

 

thanks grant,

you really helped me out big time.

I clean the throttle body, and it has seemed to fix most of my problems...

i adjusted the springs, i didnt know which one to adjust, so i did all of them.
Which is the spring i need to adjust? or is it ok adjusting all three?

thanks again man,

Rich

 

Ah, the "gunk" on the throttle disc, now that is probably all your problem was, it is a pain, and causes the disc/shaft to jam at times. That is something I am familiar with on the V12's, and on the 6cyl that gunk runs down the shaft and into the TPS, with havoc following soon after.

Just did an oil change on the X300, and removed the trunking to get at the oil filter from the top (my choice), and the throttle body is quite dirty with black scum, and it is only 5k km since last cleaned, so the "big block 3.2" is no different to the "real engine V12", mmmmm.

Maybe something sinister going on inside the engine, but at 160k kms I very much doubt it. I will continue to drive it till it drops, could be a while.

 

so,

after a good drive for a few days.

It fixed most of my problems, but i still have a problem when coasting down
a hill that the revs with go up and down till i put my foot on the gas again...

Rich

 

OK, the revs up and down on coast (over run) at 50mph in "D" is the trans going in and out of lockup, it is that critical speed that is the issue.

Mine does it also if I "coast" down a hill and the car gets to 81kph (about 50mph) it gives a "thud" as it goes into lockup, and that is all and speed increases slightly (you are going downhill after all), BUT, if I dab the brakes and reduce speed to just on 80kph it becomes undecided, and hunts a bit, like its never satisfied, so I either keep it below 80, or above 80, and all is sweet.

DONT FORGET mine is a 3.2ltr with a cable from the throttle shaft to the transmission for gear change control, and the 4ltr have this done by electronics.

I still reckon some "fresh" fluid, maybe 2 or 3 doses will sort things a tad more, and that will definately be cheaper than delving into the innards of the transmission.

Maybe it is the TPS, at the end of the day, but it sure sounds like your trans will benefit from fresh fluid no matter what.

I, and many others on these forums, have salvaged a trans by getting the fluid freshened up as soon a spossible, it is a forgotten item, much like power steer fluid, it never gets changed, and then the pump dies, and then fresh fluid arrives for another 10 years.

ALL my Jags get trans and power steer fluid changes at 2 years, no matter how many, or few kms they have done, and just basic fluids, NO fancy stuff, or additives.
I have never had a trans failure, or a pump failure, maybe I am lucky, or is it the Aussie thing, OR the clockwise rotatation of fluids versus the anti-clockwise up there, haha.

Enjoy.