Xk8 shudder after 4 miles

this is a continuation to my last topic.
1999 jaguar xk8 4.0ltr 99000 miles,
After approx 4-5 miles the car shudders like you wouldn’t believe,
work done so far;
new plugs, new coils,new fuel regulator,recon injectors, pressor test within spec,tappets within spec,all vacuum hoses checked,new fuel filter, today I replaced the gearbox oil and filter just to eliminate gearbox problems.
So no idea what to do next

Please stick to the old thread, keeps it all in order and one place, it’s not a new issue.

bit rude, I will now leave this forum

Roger,
When you say “shudder”, do you mean you’re feeling it through your steering
wheel, or the whole auto. If mostly through the wheel, it can be several things.

  1. Pirelli or Dunlop on the most used
  2. Steering system is way off, or bent
  3. Tire alignment could be way off.
  4. Tire is not “rounded” enough, needs shaving
    I know this info may not be your vibration, but it helped mine,
    as well as doing about a dozen tire warm up turns side to side
    when sitting too long will get that flat spot ironed out.
    Bob

Roger,
Hope you’ll stay with us, love to hear how it all turns out.
We all do care, just another Jag lover, even though it is a
beautiful autos, that have a few quirks, just like we humans.
Best, Bob

Roger
Have you had you wheels balanced lately? Try to find an old balancer that spins the wheel on the car. That balanced not only the wheel and tire but also the hub.
I had a similar problem and although the wheel and tire were balanced, it was the hub itself that was out.

That’s why I said stick to the old thread…

If it only shudders sfter a few km it’s not going to be an imbalance.

Thanks Len, yes had all 4 wheels balanced plus swaping them around, the bit that I can’t get my head around is it only happens after 4-5 miles and you can accelerate through it??

Just done another compression test RH bank; avg 190
LH bank ;avg 140
I’m beginning to think that the engine is the problem!

Redone the tappets all within spec except 2 inlet which are 2th tight

Are you sure it’s the engine at fault, especially since there are now no engine fault codes being recorded.

Shudder at about 1500 Rpm is indicative of the torque converter lock up clutch randomly slipping when in partial lock-up mode.
This can be a result of glycol contamination of the ATF due to a leaking transmission cooler.

A change of ATF may help, but the old fluid need a glycol test performed to be certain.
the bad news is if glycol is the cause, only a full gearbox and torque converter rebuild will fix it, as the rumble is due to the adhesive holding the friction material on has been affected by the glycol.

If possible, lock out the torque converter lock-up clutch and see if the issue is resolved…for now.

Thanks, 3 days ago I changed the gearbox oil, filter and gasket, didn’t make any difference.
Today I cleaned the Part Load Breather, took the car out, after 4 miles had a vibration and shaking through the steering wheel, now I’m thinking perhaps its not the engine.
I will check out the torque converter lock up.

Check for a dragging brake. Drive till it shudders them carefully feel each wheel to see if one is smoking hot.

Hi, thanks for your comments, however that was one of my first things to do, I’ve replaced discs and caliper refurbishment, temperature is warm on all 4 wheels.
I’m thinking it could be the steering rack, not sure how to test it.thanks again for your input.

Roger,
Don’t change anything you’re doing. But, please consider the tires, are they true
round. My 2001 and most XK8s do shimmy about, according to Jaguar dealers
in Seattle and in Victoria,BC. The last resort was to have the tires shaved to true round.
I’ve put up with mine as the shimmy is only slight. I do warm up my sidewalls, race track
style, it helps dampen the vibration.
Best, Bob

S

Bob, many thanks for your suggestions, I have this morning jacked up the car with the wheels of the ground,
set up my lathe gauge 1/2 mm off the tyre and turned the wheels slowly to check for roundness, both front tyres are perfectly round. at least that’s 1 more thing that it isn’t!!
Tyres and wheels was my first thought with this problem, hence I had all 4 balanced and swapped around, but didn’t check for roundness, so thanks again.
i have ordered a new MAS which has just arrived, i have put it in the car and cleared the codes, it is sounding better i.e. no apparent misfire. now going for a test drive, will update.

well that didn’t work, so i have to make a choice , buy a replacement engine and hope that was the problem or scrap the car.

I know you’re trolling, but it would be worthwhile to document at what road and engine speeds it happens, which gear, change under braking, change under load, situation when restarting or slowing down,…

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Great advice offered.
When you get to the shuddering, shift into neutral and assess if it made a difference. That somewhat isolates the engine from the drivetrain and might help with your troubleshooting.

thanks for your advice gents, David; road speed is anything between 50-70mph aprox 2000rpm, can be 4th or 5 gear, doesn’t change under braking, IT IS UNDER LOAD, restarting still the same, slowing down or accelerating will reduce it considerably.
mminnich; great advice as you say including yours; I’ve had a couple of days away from the car, however been out today and after 4-5 miles it starts again, took your advice and shift into neutral and it STOPS!!!
So is it the drive train (No load) or is it a engine misfire!!!

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