Sods Law Trouble

[carlo]

Hi Guys,

Just put the Mk1 LS400 back on the road after its winter rest to get ready for trip to France this weekend. Felt it wasn't performing as well as usual on its way for service. But, new set of plugs, clean air filter, general service, & it seemed ok.

BUT! get it up to normal running temp. and accelerate to 70ish, then drop down between 40 - 55 and it judders - feels like a petrol starvation but the revs are ok & it idles smoothly. Ok at low speeds, 30ish but that mid range brings back the judder. Any ideas of cause? Plugs are recommended for model. I've onl;y one day before leaving & will have to revert to Nissan Almera instead if no solution. HELP!!

Cheers,

JM

[cleverdick]

Mmmm....

Could be a number of things, and the symptom quite probably will disappear after a long run to France. Cars don't like to have a 'winter rest', they need to be exercised otherwise bad things can happen!

It could be that the throttle body needs cleaning inside (hopefully you still have time to do it) or even as simple a thing as the fuel having deteriorated in the tank. You could perhaps add some Wynn's Dry Fuel just in case there are globules of water being sucked up. What were the plugs that were put in, BTW? Denso iridium I hope!

Can't think of anything else right now, except that if the Battery has been disconnected or lost its charge then the ECU will need to re-learn your driving style for optimum performance (so I believe).

Good luck...

(C'mon everyone, let's see if we can help this guy out!)

[Alex JB]

Do you think it's definately engine related not brake discs or prop shaft rubbers deteriorated over the lay up?

Is it worse under breaking (discs) or is it under acceleration (prop shaft)...

Just a thought :)

[carlo]

Hi Guys,

Thanks for the thoughts.

I know it's a strange one. I've put additive into petrol to ensure it's not carbon build up & to clean out jets. The plugs were Denso & the Battery was kept on trickle charge over winter.

I do think it's engine related since the hesitation ( judder ) in power feels like fuel starvation. I've heard of judder from prop shaft rubbers but would that tend to occur at a certain speed or be a constant symptom?

I've always used normal unleaded petrol ( not supermarket ) 85 octane & wondered if a higher octane was needed?

What is the throttle body that might need cleaning inside?

All suggestions gratefully received - but beginning to look like a long uncomfortable trip in the Almera!

Gulp!

Cheers,

JM

[usuf_x]

From the sounds of things if your breaking down to 40-50 id say get you brake disc / pads checked

[ontheroad1]

I would change the fuel filter and definitely not use 85 octane ( 95 minimum or higher )

[carlo]

I would change the fuel filter and definitely not use 85 octane ( 95 minimum or higher )

Sorry! Meant 95.

JM

It's going into my local Lexus garage after Easter. Will reveal the fault when it's discovered & cured ( hopefully ).

Cheers,

JM

[Alex JB]

does that mean you have to go on the holiday in your Nissan ? :(

[bazgtr]

Had this problem at 48mph to 50mph. When travelling at that speed the car would judder a bit.

Have changed the trans fluid and filter and find it's a lot smoother around that speed than before. 80% better. Changes through with no judder or going down through it.

The other 20% I can feel I think is something I read over on a US site and that the early LS400(90-94) have a little judder at that speed. They mention that around 50mph is the change over point of the auto box and can't decide if you're going to go faster(Shift up) or slower(Shift down), So gets in two minds switching from the two gears. Once you go faster or slower then it's happy at that speed. You can make it worst by just resting your foot on the pedal lightly at 49MPH. M<ove the pedal either way and the judder goes.

Would like your feedback on the 50mph judder. Do you agree or not about the changing point or is there anything else we might be missing.

Trans & engine mounts may also be worth changing

[carlo]

Hi Guys,

Thanks for all the comments on this. Had to travel in the 1.4 Almera & got tennis elbow for the pleasure after 650 miles.

I don't think it's a gear shifting issue as the judder is quite pronounced. I think it's a petrol thing & hopefully just the filter. It goes fine on first use with the auto choke on but after a run & around 50 mph it judders badly. I'll probably book it into Teesside Lexus ( near Yarm ) in the next week or so if my general mechanic guy can't suss it ( rather significant differences in labour costs prompts this action ) though I'd apprerciate comments on the benefits of having a Lexus diagnostic done.

Meantime,

Thanks again for the help.

JM

[ontheroad1]

they have moved to Preston park Stockton

[carlo]

they have moved to Preston park Stockton

Thanks for that bit of information.

JM