I keep a few spare coil packs in the trunk. Since I bought the car in Jan 2021, 3 have failed. I recently changed the #8 a week ago. I bit the bullet and bought the final 5 and going to change them all out. The coil packs were original to my car.

I'm sure that someone mentioned that the adaptation readings should be checked via a scanner. If the pressure readings are off maybe that could be affecting your shifting. I'm not a transmission expert ( i have rebuilt one ) but there is a lot of ZF tranny info on YouTube.

Good Luck!

 

As has been pointed out, misfire(s) from the engine causes the TCM to go into 'limp mode' to protect the gearbox.

Another area to check is the battery voltage. Use a voltmeter to read the battery voltage across the terminals with the ignition in the OFF position. There should be a minimum of 12.6 volts present for all the modules to communicate correctly. If there's less than 12.6 volts, charge the battery for five hours at 2 to 5 amps and retest. If there's still less than 12.6 volts showing, replace the battery.

 

Problem solved, It was the coil. The car ran great the morning after sitting all night on a cold start. Now I feel much better spending the money to finish fixing all the other problems.
Oil leak at the oil filter housing
Rebuild suspension air pump
Upper control arms
Squeaky brakes, rust build-up from sitting for 6 months
I'm thinking of powder coating the wheels with a dark bronze color to give it a little more modern feel. I'm still thinking about this and I would like to hear some comments.
The front and rear bumper have some paintwork as well and the crease in the rear driver's door (see photos). I have a dent guy coming today to look at. I showed him a photo and he thinks he can get out because it's aluminum it has a little more flex.
Finish it off by tinting the windows all around to go with the darker wheels.
The tires could be replaced but I'm going to wait on that.
Thanks for all the help and comments.

 

That is an incredible looking $200 XJ... good to see the progress! Totally worth keeping the momentum going and sorting the car. Check out the TSBs attached that RoadMaster2 shared with me in my thread yesterday on clearing the drains. And I'd keep those wheels the stock finish as they complement the car beautifully. I have the same ones in chrome and wish mine were that silver finish. Unless the tires are more than several years old (check the date codes on the sidewall) for safety purposes or rock solid, I'd get the car mechanically sorted otherwise first and do those last as a cherry on top. Looks stunning without the tint in that color combo, but 30% all around is a good finishing touch if needed.

 

The tires are old, I think they are seven years old and they have about 30% tread left. I have checked all the drains and we are all good there. I would like to see some photos of Champian colored XJ8 with darker color wheels to see if I like it or not. I have a 2000 XKR that I redid the wheels to match the dark gray trim color and I just love it and I get a lot of compliments on the color. the old ones the chrome was peeling off so I needed to do something. I think this car would make a great rental car on Turo. I have done some Turo cars in the past and had good luck. Just a thought. I should have all the mechanical issues sorted by Christmas. I will keep the progress updated as I move along. thanks for the info and the encouragement.

 

I've seen other X350s for less than $1000 but they always have dirty/worn interiors that are sad, sad, sad. Yours looks fabulous. My Platinum '05 had darker wheels, and they looked great. PO had a younger son who insisted it would make the car look more up-to-date, and he wasn't wrong. Problem was, PO then had trouble selling it to the traditionalists, which explains why it took a while to sell, and why I got a steep discount. My new '08 has chrome wheels, and I'm leaving them alone. The whole car has too much bling for the younger set, but I'm not a member of that group. Original bling looks great to my eyes.